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• How to Write a Literature Review | Guide, Examples, & Templates

How to Write a Literature Review | Guide, Examples, & Templates

Published on January 2, 2023 by Shona McCombes . Revised on September 11, 2023.

What is a literature review? A literature review is a survey of scholarly sources on a specific topic. It provides an overview of current knowledge, allowing you to identify relevant theories, methods, and gaps in the existing research that you can later apply to your paper, thesis, or dissertation topic .

There are five key steps to writing a literature review:

• Search for relevant literature
• Evaluate sources
• Identify themes, debates, and gaps
• Outline the structure
• Write your literature review

A good literature review doesn’t just summarize sources—it analyzes, synthesizes , and critically evaluates to give a clear picture of the state of knowledge on the subject.

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Table of contents

What is the purpose of a literature review, examples of literature reviews, step 1 – search for relevant literature, step 2 – evaluate and select sources, step 3 – identify themes, debates, and gaps, step 4 – outline your literature review’s structure, step 5 – write your literature review, free lecture slides, other interesting articles, frequently asked questions, introduction.

• Quick Run-through
• Step 1 & 2

When you write a thesis , dissertation , or research paper , you will likely have to conduct a literature review to situate your research within existing knowledge. The literature review gives you a chance to:

• Demonstrate your familiarity with the topic and its scholarly context
• Develop a theoretical framework and methodology for your research
• Position your work in relation to other researchers and theorists
• Show how your research addresses a gap or contributes to a debate
• Evaluate the current state of research and demonstrate your knowledge of the scholarly debates around your topic.

Writing literature reviews is a particularly important skill if you want to apply for graduate school or pursue a career in research. We’ve written a step-by-step guide that you can follow below.

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Writing literature reviews can be quite challenging! A good starting point could be to look at some examples, depending on what kind of literature review you’d like to write.

• Example literature review #1: “Why Do People Migrate? A Review of the Theoretical Literature” ( Theoretical literature review about the development of economic migration theory from the 1950s to today.)
• Example literature review #2: “Literature review as a research methodology: An overview and guidelines” ( Methodological literature review about interdisciplinary knowledge acquisition and production.)
• Example literature review #3: “The Use of Technology in English Language Learning: A Literature Review” ( Thematic literature review about the effects of technology on language acquisition.)
• Example literature review #4: “Learners’ Listening Comprehension Difficulties in English Language Learning: A Literature Review” ( Chronological literature review about how the concept of listening skills has changed over time.)

You can also check out our templates with literature review examples and sample outlines at the links below.

Download Word doc Download Google doc

Before you begin searching for literature, you need a clearly defined topic .

If you are writing the literature review section of a dissertation or research paper, you will search for literature related to your research problem and questions .

Make a list of keywords

Start by creating a list of keywords related to your research question. Include each of the key concepts or variables you’re interested in, and list any synonyms and related terms. You can add to this list as you discover new keywords in the process of your literature search.

• Social media, Facebook, Instagram, Twitter, Snapchat, TikTok
• Body image, self-perception, self-esteem, mental health
• Generation Z, teenagers, adolescents, youth

Search for relevant sources

Use your keywords to begin searching for sources. Some useful databases to search for journals and articles include:

• Your university’s library catalogue
• Google Scholar
• Project Muse (humanities and social sciences)
• Medline (life sciences and biomedicine)
• EconLit (economics)
• Inspec (physics, engineering and computer science)

You can also use boolean operators to help narrow down your search.

Make sure to read the abstract to find out whether an article is relevant to your question. When you find a useful book or article, you can check the bibliography to find other relevant sources.

You likely won’t be able to read absolutely everything that has been written on your topic, so it will be necessary to evaluate which sources are most relevant to your research question.

For each publication, ask yourself:

• What question or problem is the author addressing?
• What are the key concepts and how are they defined?
• What are the key theories, models, and methods?
• Does the research use established frameworks or take an innovative approach?
• What are the results and conclusions of the study?
• How does the publication relate to other literature in the field? Does it confirm, add to, or challenge established knowledge?
• What are the strengths and weaknesses of the research?

Make sure the sources you use are credible , and make sure you read any landmark studies and major theories in your field of research.

You can use our template to summarize and evaluate sources you’re thinking about using. Click on either button below to download.

Take notes and cite your sources

As you read, you should also begin the writing process. Take notes that you can later incorporate into the text of your literature review.

It is important to keep track of your sources with citations to avoid plagiarism . It can be helpful to make an annotated bibliography , where you compile full citation information and write a paragraph of summary and analysis for each source. This helps you remember what you read and saves time later in the process.

Prevent plagiarism. Run a free check.

To begin organizing your literature review’s argument and structure, be sure you understand the connections and relationships between the sources you’ve read. Based on your reading and notes, you can look for:

• Trends and patterns (in theory, method or results): do certain approaches become more or less popular over time?
• Themes: what questions or concepts recur across the literature?
• Debates, conflicts and contradictions: where do sources disagree?
• Pivotal publications: are there any influential theories or studies that changed the direction of the field?
• Gaps: what is missing from the literature? Are there weaknesses that need to be addressed?

This step will help you work out the structure of your literature review and (if applicable) show how your own research will contribute to existing knowledge.

• Most research has focused on young women.
• There is an increasing interest in the visual aspects of social media.
• But there is still a lack of robust research on highly visual platforms like Instagram and Snapchat—this is a gap that you could address in your own research.

There are various approaches to organizing the body of a literature review. Depending on the length of your literature review, you can combine several of these strategies (for example, your overall structure might be thematic, but each theme is discussed chronologically).

Chronological

The simplest approach is to trace the development of the topic over time. However, if you choose this strategy, be careful to avoid simply listing and summarizing sources in order.

Try to analyze patterns, turning points and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred.

If you have found some recurring central themes, you can organize your literature review into subsections that address different aspects of the topic.

For example, if you are reviewing literature about inequalities in migrant health outcomes, key themes might include healthcare policy, language barriers, cultural attitudes, legal status, and economic access.

Methodological

If you draw your sources from different disciplines or fields that use a variety of research methods , you might want to compare the results and conclusions that emerge from different approaches. For example:

• Look at what results have emerged in qualitative versus quantitative research
• Discuss how the topic has been approached by empirical versus theoretical scholarship
• Divide the literature into sociological, historical, and cultural sources

Theoretical

A literature review is often the foundation for a theoretical framework . You can use it to discuss various theories, models, and definitions of key concepts.

You might argue for the relevance of a specific theoretical approach, or combine various theoretical concepts to create a framework for your research.

Like any other academic text , your literature review should have an introduction , a main body, and a conclusion . What you include in each depends on the objective of your literature review.

The introduction should clearly establish the focus and purpose of the literature review.

Depending on the length of your literature review, you might want to divide the body into subsections. You can use a subheading for each theme, time period, or methodological approach.

As you write, you can follow these tips:

• Summarize and synthesize: give an overview of the main points of each source and combine them into a coherent whole
• Analyze and interpret: don’t just paraphrase other researchers — add your own interpretations where possible, discussing the significance of findings in relation to the literature as a whole
• Critically evaluate: mention the strengths and weaknesses of your sources
• Write in well-structured paragraphs: use transition words and topic sentences to draw connections, comparisons and contrasts

In the conclusion, you should summarize the key findings you have taken from the literature and emphasize their significance.

When you’ve finished writing and revising your literature review, don’t forget to proofread thoroughly before submitting. Not a language expert? Check out Scribbr’s professional proofreading services !

This article has been adapted into lecture slides that you can use to teach your students about writing a literature review.

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If you want to know more about the research process , methodology , research bias , or statistics , make sure to check out some of our other articles with explanations and examples.

• Sampling methods
• Simple random sampling
• Stratified sampling
• Cluster sampling
• Likert scales
• Reproducibility

 Statistics

• Null hypothesis
• Statistical power
• Probability distribution
• Effect size
• Poisson distribution

Research bias

• Optimism bias
• Cognitive bias
• Implicit bias
• Hawthorne effect
• Anchoring bias
• Explicit bias

A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .

It is often written as part of a thesis, dissertation , or research paper , in order to situate your work in relation to existing knowledge.

There are several reasons to conduct a literature review at the beginning of a research project:

• To familiarize yourself with the current state of knowledge on your topic
• To ensure that you’re not just repeating what others have already done
• To identify gaps in knowledge and unresolved problems that your research can address
• To develop your theoretical framework and methodology
• To provide an overview of the key findings and debates on the topic

Writing the literature review shows your reader how your work relates to existing research and what new insights it will contribute.

The literature review usually comes near the beginning of your thesis or dissertation . After the introduction , it grounds your research in a scholarly field and leads directly to your theoretical framework or methodology .

A literature review is a survey of credible sources on a topic, often used in dissertations , theses, and research papers . Literature reviews give an overview of knowledge on a subject, helping you identify relevant theories and methods, as well as gaps in existing research. Literature reviews are set up similarly to other  academic texts , with an introduction , a main body, and a conclusion .

An  annotated bibliography is a list of  source references that has a short description (called an annotation ) for each of the sources. It is often assigned as part of the research process for a  paper .  

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A literature review is a document or section of a document that collects key sources on a topic and discusses those sources in conversation with each other (also called synthesis ). The lit review is an important genre in many disciplines, not just literature (i.e., the study of works of literature such as novels and plays). When we say “literature review” or refer to “the literature,” we are talking about the research ( scholarship ) in a given field. You will often see the terms “the research,” “the scholarship,” and “the literature” used mostly interchangeably.

Where, when, and why would I write a lit review?

There are a number of different situations where you might write a literature review, each with slightly different expectations; different disciplines, too, have field-specific expectations for what a literature review is and does. For instance, in the humanities, authors might include more overt argumentation and interpretation of source material in their literature reviews, whereas in the sciences, authors are more likely to report study designs and results in their literature reviews; these differences reflect these disciplines’ purposes and conventions in scholarship. You should always look at examples from your own discipline and talk to professors or mentors in your field to be sure you understand your discipline’s conventions, for literature reviews as well as for any other genre.

A literature review can be a part of a research paper or scholarly article, usually falling after the introduction and before the research methods sections. In these cases, the lit review just needs to cover scholarship that is important to the issue you are writing about; sometimes it will also cover key sources that informed your research methodology.

Lit reviews can also be standalone pieces, either as assignments in a class or as publications. In a class, a lit review may be assigned to help students familiarize themselves with a topic and with scholarship in their field, get an idea of the other researchers working on the topic they’re interested in, find gaps in existing research in order to propose new projects, and/or develop a theoretical framework and methodology for later research. As a publication, a lit review usually is meant to help make other scholars’ lives easier by collecting and summarizing, synthesizing, and analyzing existing research on a topic. This can be especially helpful for students or scholars getting into a new research area, or for directing an entire community of scholars toward questions that have not yet been answered.

What are the parts of a lit review?

Most lit reviews use a basic introduction-body-conclusion structure; if your lit review is part of a larger paper, the introduction and conclusion pieces may be just a few sentences while you focus most of your attention on the body. If your lit review is a standalone piece, the introduction and conclusion take up more space and give you a place to discuss your goals, research methods, and conclusions separately from where you discuss the literature itself.

Introduction:

• An introductory paragraph that explains what your working topic and thesis is
• A forecast of key topics or texts that will appear in the review
• Potentially, a description of how you found sources and how you analyzed them for inclusion and discussion in the review (more often found in published, standalone literature reviews than in lit review sections in an article or research paper)
• Summarize and synthesize: Give an overview of the main points of each source and combine them into a coherent whole
• Analyze and interpret: Don’t just paraphrase other researchers – add your own interpretations where possible, discussing the significance of findings in relation to the literature as a whole
• Critically Evaluate: Mention the strengths and weaknesses of your sources
• Write in well-structured paragraphs: Use transition words and topic sentence to draw connections, comparisons, and contrasts.

Conclusion:

• Summarize the key findings you have taken from the literature and emphasize their significance
• Connect it back to your primary research question

How should I organize my lit review?

Lit reviews can take many different organizational patterns depending on what you are trying to accomplish with the review. Here are some examples:

• Chronological : The simplest approach is to trace the development of the topic over time, which helps familiarize the audience with the topic (for instance if you are introducing something that is not commonly known in your field). If you choose this strategy, be careful to avoid simply listing and summarizing sources in order. Try to analyze the patterns, turning points, and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred (as mentioned previously, this may not be appropriate in your discipline — check with a teacher or mentor if you’re unsure).
• Thematic : If you have found some recurring central themes that you will continue working with throughout your piece, you can organize your literature review into subsections that address different aspects of the topic. For example, if you are reviewing literature about women and religion, key themes can include the role of women in churches and the religious attitude towards women.
• Qualitative versus quantitative research
• Empirical versus theoretical scholarship
• Divide the research by sociological, historical, or cultural sources
• Theoretical : In many humanities articles, the literature review is the foundation for the theoretical framework. You can use it to discuss various theories, models, and definitions of key concepts. You can argue for the relevance of a specific theoretical approach or combine various theorical concepts to create a framework for your research.

What are some strategies or tips I can use while writing my lit review?

Any lit review is only as good as the research it discusses; make sure your sources are well-chosen and your research is thorough. Don’t be afraid to do more research if you discover a new thread as you’re writing. More info on the research process is available in our "Conducting Research" resources .

As you’re doing your research, create an annotated bibliography ( see our page on the this type of document ). Much of the information used in an annotated bibliography can be used also in a literature review, so you’ll be not only partially drafting your lit review as you research, but also developing your sense of the larger conversation going on among scholars, professionals, and any other stakeholders in your topic.

Usually you will need to synthesize research rather than just summarizing it. This means drawing connections between sources to create a picture of the scholarly conversation on a topic over time. Many student writers struggle to synthesize because they feel they don’t have anything to add to the scholars they are citing; here are some strategies to help you:

• It often helps to remember that the point of these kinds of syntheses is to show your readers how you understand your research, to help them read the rest of your paper.
• Writing teachers often say synthesis is like hosting a dinner party: imagine all your sources are together in a room, discussing your topic. What are they saying to each other?
• Look at the in-text citations in each paragraph. Are you citing just one source for each paragraph? This usually indicates summary only. When you have multiple sources cited in a paragraph, you are more likely to be synthesizing them (not always, but often
• Read more about synthesis here.

The most interesting literature reviews are often written as arguments (again, as mentioned at the beginning of the page, this is discipline-specific and doesn’t work for all situations). Often, the literature review is where you can establish your research as filling a particular gap or as relevant in a particular way. You have some chance to do this in your introduction in an article, but the literature review section gives a more extended opportunity to establish the conversation in the way you would like your readers to see it. You can choose the intellectual lineage you would like to be part of and whose definitions matter most to your thinking (mostly humanities-specific, but this goes for sciences as well). In addressing these points, you argue for your place in the conversation, which tends to make the lit review more compelling than a simple reporting of other sources.

Literature Review

• What is a Literature Review?
• What is a good literature review?
• Types of Literature Reviews
• What are the parts of a Literature Review?
• What is the difference between a Systematic Review and a Literature Review?

Parts of a Literature Review

Introduction      .

• To explain the focus and establish the importance of the subject
• provide the framework, selection criteria, or parameters of your literature review
• provide background or history
• outline what kind of work has been done on the topic
• briefly identify any controversies within the field or any recent research that has raised questions about earlier assumptions
• In a stand-alone literature review, this statement will sum up and evaluate the current state of this field of research
• In a review that is an introduction or preparatory to a thesis or research report, it will suggest how the review findings will lead to the research the writer proposes to undertake.
• To summarize and evaluate the current state of knowledge in the field
• To note major themes or topics, the most important trends, and any findings about which researchers agree or disagree
• Often divided by headings/subheadings
• If the review is preliminary to your own thesis or research project, its purpose is to make an argument that will justify your proposed research. Therefore, the literature review will discuss only that research which leads directly to your own project.
• To summarize the evidence presented and show its significance
• Rather than restating your thesis or purpose statement, explain what your review tells you about the current state of the field
• If the review is an introduction to your own research, the conclusion highlights gaps and indicates how previous research leads to your own research project and chosen methodology. 
• If the review is a stand-alone assignment for a course, the conclusion should suggest any practical applications of the research as well as the implications and possibilities for future research.
• Find out what style guide you are required to follow (e.g., APA, MLA, ASA)
• Follow the guidelines to format citations and create a reference list or bibliography
• Cite Your Sources

This work is licensed under a  Creative Commons Attribution-NonCommercial-ShareAlike 4.0  International License. adapted from UofG,McLaughlin Library

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The Research Proposal

83 Components of the Literature Review

Krathwohl (2005) suggests and describes a variety of components to include in a research proposal.  The following sections present these components in a suggested template for you to follow in the preparation of your research proposal.

Introduction

The introduction sets the tone for what follows in your research proposal – treat it as the initial pitch of your idea.  After reading the introduction your reader should:

• Understand what it is you want to do;
• Have a sense of your passion for the topic;
• Be excited about the study´s possible outcomes.

As you begin writing your research proposal it is helpful to think of the introduction as a narrative of what it is you want to do, written in one to three paragraphs.  Within those one to three paragraphs, it is important to briefly answer the following questions:

• What is the central research problem?
• How is the topic of your research proposal related to the problem?
• What methods will you utilize to analyze the research problem?
• Why is it important to undertake this research? What is the significance of your proposed research?  Why are the outcomes of your proposed research important, and to whom or to what are they important?

Note : You may be asked by your instructor to include an abstract with your research proposal.  In such cases, an abstract should provide an overview of what it is you plan to study, your main research question, a brief explanation of your methods to answer the research question, and your expected findings. All of this information must be carefully crafted in 150 to 250 words.  A word of advice is to save the writing of your abstract until the very end of your research proposal preparation.  If you are asked to provide an abstract, you should include 5-7 key words that are of most relevance to your study. List these in order of relevance.

Background and significance

The purpose of this section is to explain the context of your proposal and to describe, in detail, why it is important to undertake this research. Assume that the person or people who will read your research proposal know nothing or very little about the research problem.  While you do not need to include all knowledge you have learned about your topic in this section, it is important to ensure that you include the most relevant material that will help to explain the goals of your research.

While there are no hard and fast rules, you should attempt to address some or all of the following key points:

• State the research problem and provide a more thorough explanation about the purpose of the study than what you stated in the introduction.
• Present the rationale for the proposed research study. Clearly indicate why this research is worth doing.  Answer the “so what?” question.
• Describe the major issues or problems to be addressed by your research. Do not forget to explain how and in what ways your proposed research builds upon previous related research.
• Explain how you plan to go about conducting your research.
• Clearly identify the key or most relevant sources of research you intend to use and explain how they will contribute to your analysis of the topic.
• Set the boundaries of your proposed research, in order to provide a clear focus. Where appropriate, state not only what you will study, but what will be excluded from your study.
• Provide clear definitions of key concepts and terms. As key concepts and terms often have numerous definitions, make sure you state which definition you will be utilizing in your research.

Literature Review

This is the most time-consuming aspect in the preparation of your research proposal and it is a key component of the research proposal. As described in Chapter 5 , the literature review provides the background to your study and demonstrates the significance of the proposed research. Specifically, it is a review and synthesis of prior research that is related to the problem you are setting forth to investigate.  Essentially, your goal in the literature review is to place your research study within the larger whole of what has been studied in the past, while demonstrating to your reader that your work is original, innovative, and adds to the larger whole.

As the literature review is information dense, it is essential that this section be intelligently structured to enable your reader to grasp the key arguments underpinning your study. However, this can be easier to state and harder to do, simply due to the fact there is usually a plethora of related research to sift through. Consequently, a good strategy for writing the literature review is to break the literature into conceptual categories or themes, rather than attempting to describe various groups of literature you reviewed.  Chapter V, “ The Literature Review ,” describes a variety of methods to help you organize the themes.

Here are some suggestions on how to approach the writing of your literature review:

• Think about what questions other researchers have asked, what methods they used, what they found, and what they recommended based upon their findings.
• Do not be afraid to challenge previous related research findings and/or conclusions.
• Assess what you believe to be missing from previous research and explain how your research fills in this gap and/or extends previous research

It is important to note that a significant challenge related to undertaking a literature review is knowing when to stop.  As such, it is important to know how to know when you have uncovered the key conceptual categories underlying your research topic.  Generally, when you start to see repetition in the conclusions or recommendations, you can have confidence that you have covered all of the significant conceptual categories in your literature review.  However, it is also important to acknowledge that researchers often find themselves returning to the literature as they collect and analyze their data.  For example, an unexpected finding may develop as one collects and/or analyzes the data and it is important to take the time to step back and review the literature again, to ensure that no other researchers have found a similar finding.  This may include looking to research outside your field.

This situation occurred with one of the authors of this textbook´s research related to community resilience.  During the interviews, the researchers heard many participants discuss individual resilience factors and how they believed these individual factors helped make the community more resilient, overall.  Sheppard and Williams (2016) had not discovered these individual factors in their original literature review on community and environmental resilience. However, when they returned to the literature to search for individual resilience factors, they discovered a small body of literature in the child and youth psychology field. Consequently, Sheppard and Williams had to go back and add a new section to their literature review on individual resilience factors. Interestingly, their research appeared to be the first research to link individual resilience factors with community resilience factors.

Research design and methods

The objective of this section of the research proposal is to convince the reader that your overall research design and methods of analysis will enable you to solve the research problem you have identified and also enable you to accurately and effectively interpret the results of your research. Consequently, it is critical that the research design and methods section is well-written, clear, and logically organized.  This demonstrates to your reader that you know what you are going to do and how you are going to do it.  Overall, you want to leave your reader feeling confident that you have what it takes to get this research study completed in a timely fashion.

Essentially, this section of the research proposal should be clearly tied to the specific objectives of your study; however, it is also important to draw upon and include examples from the literature review that relate to your design and intended methods.  In other words, you must clearly demonstrate how your study utilizes and builds upon past studies, as it relates to the research design and intended methods.  For example, what methods have been used by other researchers in similar studies?

While it is important to consider the methods that other researchers have employed, it is equally important, if not more so, to consider what methods have not been employed but could be.  Remember, the methods section is not simply a list of tasks to be undertaken. It is also an argument as to why and how the tasks you have outlined will help you investigate the research problem and answer your research question(s).

Tips for writing the research design and methods section:

• Specify the methodological approaches you intend to employ to obtain information and the techniques you will use to analyze the data.
• Specify the research operations you will undertake and he way you will interpret the results of those operations in relation to the research problem.
• Go beyond stating what you hope to achieve through the methods you have chosen. State how you will actually do the methods (i.e. coding interview text, running regression analysis, etc.).
• Anticipate and acknowledge any potential barriers you may encounter when undertaking your research and describe how you will address these barriers.
• Explain where you believe you will find challenges related to data collection, including access to participants and information.

Preliminary suppositions and implications

The purpose of this section is to argue how and in what ways you anticipate that your research will refine, revise, or extend existing knowledge in the area of your study. Depending upon the aims and objectives of your study, you should also discuss how your anticipated findings may impact future research.  For example, is it possible that your research may lead to a new policy, new theoretical understanding, or a new method for analyzing data?  How might your study influence future studies?  What might your study mean for future practitioners working in the field?  Who or what may benefit from your study?  How might your study contribute to social, economic, environmental issues?  While it is important to think about and discuss possibilities such as these, it is equally important to be realistic in stating your anticipated findings.  In other words, you do not want to delve into idle speculation.  Rather, the purpose here is to reflect upon gaps in the current body of literature and to describe how and in what ways you anticipate your research will begin to fill in some or all of those gaps.

The conclusion reiterates the importance and significance of your research proposal and it provides a brief summary of the entire proposed study.  Essentially, this section should only be one or two paragraphs in length. Here is a potential outline for your conclusion:

• Discuss why the study should be done. Specifically discuss how you expect your study will advance existing knowledge and how your study is unique.
• Explain the specific purpose of the study and the research questions that the study will answer.
• Explain why the research design and methods chosen for this study are appropriate, and why other design and methods were not chosen.
• State the potential implications you expect to emerge from your proposed study,
• Provide a sense of how your study fits within the broader scholarship currently in existence related to the research problem.

As with any scholarly research paper, you must cite the sources you used in composing your research proposal.  In a research proposal, this can take two forms: a reference list or a bibliography.  A reference list does what the name suggests, it lists the literature you referenced in the body of your research proposal.  All references in the reference list, must appear in the body of the research proposal.  Remember, it is not acceptable to say “as cited in …”  As a researcher you must always go to the original source and check it for yourself.  Many errors are made in referencing, even by top researchers, and so it is important not to perpetuate an error made by someone else. While this can be time consuming, it is the proper way to undertake a literature review.

In contrast, a bibliography , is a list of everything you used or cited in your research proposal, with additional citations to any key sources relevant to understanding the research problem.  In other words, sources cited in your bibliography may not necessarily appear in the body of your research proposal.  Make sure you check with your instructor to see which of the two you are expected to produce.

Overall, your list of citations should be a testament to the fact that you have done a sufficient level of preliminary research to ensure that your project will complement, but not duplicate, previous research efforts. For social sciences, the reference list or bibliography should be prepared in American Psychological Association (APA) referencing format. Usually, the reference list (or bibliography) is not included in the word count of the research proposal. Again, make sure you check with your instructor to confirm.

An Introduction to Research Methods in Sociology Copyright © 2019 by Valerie A. Sheppard is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

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Literature Reviews

What this handout is about.

This handout will explain what literature reviews are and offer insights into the form and construction of literature reviews in the humanities, social sciences, and sciences.

Introduction

OK. You’ve got to write a literature review. You dust off a novel and a book of poetry, settle down in your chair, and get ready to issue a “thumbs up” or “thumbs down” as you leaf through the pages. “Literature review” done. Right?

Wrong! The “literature” of a literature review refers to any collection of materials on a topic, not necessarily the great literary texts of the world. “Literature” could be anything from a set of government pamphlets on British colonial methods in Africa to scholarly articles on the treatment of a torn ACL. And a review does not necessarily mean that your reader wants you to give your personal opinion on whether or not you liked these sources.

What is a literature review, then?

A literature review discusses published information in a particular subject area, and sometimes information in a particular subject area within a certain time period.

A literature review can be just a simple summary of the sources, but it usually has an organizational pattern and combines both summary and synthesis. A summary is a recap of the important information of the source, but a synthesis is a re-organization, or a reshuffling, of that information. It might give a new interpretation of old material or combine new with old interpretations. Or it might trace the intellectual progression of the field, including major debates. And depending on the situation, the literature review may evaluate the sources and advise the reader on the most pertinent or relevant.

But how is a literature review different from an academic research paper?

The main focus of an academic research paper is to develop a new argument, and a research paper is likely to contain a literature review as one of its parts. In a research paper, you use the literature as a foundation and as support for a new insight that you contribute. The focus of a literature review, however, is to summarize and synthesize the arguments and ideas of others without adding new contributions.

Why do we write literature reviews?

Literature reviews provide you with a handy guide to a particular topic. If you have limited time to conduct research, literature reviews can give you an overview or act as a stepping stone. For professionals, they are useful reports that keep them up to date with what is current in the field. For scholars, the depth and breadth of the literature review emphasizes the credibility of the writer in his or her field. Literature reviews also provide a solid background for a research paper’s investigation. Comprehensive knowledge of the literature of the field is essential to most research papers.

Who writes these things, anyway?

Literature reviews are written occasionally in the humanities, but mostly in the sciences and social sciences; in experiment and lab reports, they constitute a section of the paper. Sometimes a literature review is written as a paper in itself.

Let’s get to it! What should I do before writing the literature review?

If your assignment is not very specific, seek clarification from your instructor:

• Roughly how many sources should you include?
• What types of sources (books, journal articles, websites)?
• Should you summarize, synthesize, or critique your sources by discussing a common theme or issue?
• Should you evaluate your sources?
• Should you provide subheadings and other background information, such as definitions and/or a history?

Find models

Look for other literature reviews in your area of interest or in the discipline and read them to get a sense of the types of themes you might want to look for in your own research or ways to organize your final review. You can simply put the word “review” in your search engine along with your other topic terms to find articles of this type on the Internet or in an electronic database. The bibliography or reference section of sources you’ve already read are also excellent entry points into your own research.

Narrow your topic

There are hundreds or even thousands of articles and books on most areas of study. The narrower your topic, the easier it will be to limit the number of sources you need to read in order to get a good survey of the material. Your instructor will probably not expect you to read everything that’s out there on the topic, but you’ll make your job easier if you first limit your scope.

Keep in mind that UNC Libraries have research guides and to databases relevant to many fields of study. You can reach out to the subject librarian for a consultation: https://library.unc.edu/support/consultations/ .

And don’t forget to tap into your professor’s (or other professors’) knowledge in the field. Ask your professor questions such as: “If you had to read only one book from the 90’s on topic X, what would it be?” Questions such as this help you to find and determine quickly the most seminal pieces in the field.

Consider whether your sources are current

Some disciplines require that you use information that is as current as possible. In the sciences, for instance, treatments for medical problems are constantly changing according to the latest studies. Information even two years old could be obsolete. However, if you are writing a review in the humanities, history, or social sciences, a survey of the history of the literature may be what is needed, because what is important is how perspectives have changed through the years or within a certain time period. Try sorting through some other current bibliographies or literature reviews in the field to get a sense of what your discipline expects. You can also use this method to consider what is currently of interest to scholars in this field and what is not.

Strategies for writing the literature review

Find a focus.

A literature review, like a term paper, is usually organized around ideas, not the sources themselves as an annotated bibliography would be organized. This means that you will not just simply list your sources and go into detail about each one of them, one at a time. No. As you read widely but selectively in your topic area, consider instead what themes or issues connect your sources together. Do they present one or different solutions? Is there an aspect of the field that is missing? How well do they present the material and do they portray it according to an appropriate theory? Do they reveal a trend in the field? A raging debate? Pick one of these themes to focus the organization of your review.

Convey it to your reader

A literature review may not have a traditional thesis statement (one that makes an argument), but you do need to tell readers what to expect. Try writing a simple statement that lets the reader know what is your main organizing principle. Here are a couple of examples:

The current trend in treatment for congestive heart failure combines surgery and medicine. More and more cultural studies scholars are accepting popular media as a subject worthy of academic consideration.

Consider organization

You’ve got a focus, and you’ve stated it clearly and directly. Now what is the most effective way of presenting the information? What are the most important topics, subtopics, etc., that your review needs to include? And in what order should you present them? Develop an organization for your review at both a global and local level:

First, cover the basic categories

Just like most academic papers, literature reviews also must contain at least three basic elements: an introduction or background information section; the body of the review containing the discussion of sources; and, finally, a conclusion and/or recommendations section to end the paper. The following provides a brief description of the content of each:

• Introduction: Gives a quick idea of the topic of the literature review, such as the central theme or organizational pattern.
• Body: Contains your discussion of sources and is organized either chronologically, thematically, or methodologically (see below for more information on each).
• Conclusions/Recommendations: Discuss what you have drawn from reviewing literature so far. Where might the discussion proceed?

Organizing the body

Once you have the basic categories in place, then you must consider how you will present the sources themselves within the body of your paper. Create an organizational method to focus this section even further.

To help you come up with an overall organizational framework for your review, consider the following scenario:

You’ve decided to focus your literature review on materials dealing with sperm whales. This is because you’ve just finished reading Moby Dick, and you wonder if that whale’s portrayal is really real. You start with some articles about the physiology of sperm whales in biology journals written in the 1980’s. But these articles refer to some British biological studies performed on whales in the early 18th century. So you check those out. Then you look up a book written in 1968 with information on how sperm whales have been portrayed in other forms of art, such as in Alaskan poetry, in French painting, or on whale bone, as the whale hunters in the late 19th century used to do. This makes you wonder about American whaling methods during the time portrayed in Moby Dick, so you find some academic articles published in the last five years on how accurately Herman Melville portrayed the whaling scene in his novel.

Now consider some typical ways of organizing the sources into a review:

• Chronological: If your review follows the chronological method, you could write about the materials above according to when they were published. For instance, first you would talk about the British biological studies of the 18th century, then about Moby Dick, published in 1851, then the book on sperm whales in other art (1968), and finally the biology articles (1980s) and the recent articles on American whaling of the 19th century. But there is relatively no continuity among subjects here. And notice that even though the sources on sperm whales in other art and on American whaling are written recently, they are about other subjects/objects that were created much earlier. Thus, the review loses its chronological focus.
• By publication: Order your sources by publication chronology, then, only if the order demonstrates a more important trend. For instance, you could order a review of literature on biological studies of sperm whales if the progression revealed a change in dissection practices of the researchers who wrote and/or conducted the studies.
• By trend: A better way to organize the above sources chronologically is to examine the sources under another trend, such as the history of whaling. Then your review would have subsections according to eras within this period. For instance, the review might examine whaling from pre-1600-1699, 1700-1799, and 1800-1899. Under this method, you would combine the recent studies on American whaling in the 19th century with Moby Dick itself in the 1800-1899 category, even though the authors wrote a century apart.
• Thematic: Thematic reviews of literature are organized around a topic or issue, rather than the progression of time. However, progression of time may still be an important factor in a thematic review. For instance, the sperm whale review could focus on the development of the harpoon for whale hunting. While the study focuses on one topic, harpoon technology, it will still be organized chronologically. The only difference here between a “chronological” and a “thematic” approach is what is emphasized the most: the development of the harpoon or the harpoon technology.But more authentic thematic reviews tend to break away from chronological order. For instance, a thematic review of material on sperm whales might examine how they are portrayed as “evil” in cultural documents. The subsections might include how they are personified, how their proportions are exaggerated, and their behaviors misunderstood. A review organized in this manner would shift between time periods within each section according to the point made.
• Methodological: A methodological approach differs from the two above in that the focusing factor usually does not have to do with the content of the material. Instead, it focuses on the “methods” of the researcher or writer. For the sperm whale project, one methodological approach would be to look at cultural differences between the portrayal of whales in American, British, and French art work. Or the review might focus on the economic impact of whaling on a community. A methodological scope will influence either the types of documents in the review or the way in which these documents are discussed. Once you’ve decided on the organizational method for the body of the review, the sections you need to include in the paper should be easy to figure out. They should arise out of your organizational strategy. In other words, a chronological review would have subsections for each vital time period. A thematic review would have subtopics based upon factors that relate to the theme or issue.

Sometimes, though, you might need to add additional sections that are necessary for your study, but do not fit in the organizational strategy of the body. What other sections you include in the body is up to you. Put in only what is necessary. Here are a few other sections you might want to consider:

• Current Situation: Information necessary to understand the topic or focus of the literature review.
• History: The chronological progression of the field, the literature, or an idea that is necessary to understand the literature review, if the body of the literature review is not already a chronology.
• Methods and/or Standards: The criteria you used to select the sources in your literature review or the way in which you present your information. For instance, you might explain that your review includes only peer-reviewed articles and journals.

Questions for Further Research: What questions about the field has the review sparked? How will you further your research as a result of the review?

Begin composing

Once you’ve settled on a general pattern of organization, you’re ready to write each section. There are a few guidelines you should follow during the writing stage as well. Here is a sample paragraph from a literature review about sexism and language to illuminate the following discussion:

However, other studies have shown that even gender-neutral antecedents are more likely to produce masculine images than feminine ones (Gastil, 1990). Hamilton (1988) asked students to complete sentences that required them to fill in pronouns that agreed with gender-neutral antecedents such as “writer,” “pedestrian,” and “persons.” The students were asked to describe any image they had when writing the sentence. Hamilton found that people imagined 3.3 men to each woman in the masculine “generic” condition and 1.5 men per woman in the unbiased condition. Thus, while ambient sexism accounted for some of the masculine bias, sexist language amplified the effect. (Source: Erika Falk and Jordan Mills, “Why Sexist Language Affects Persuasion: The Role of Homophily, Intended Audience, and Offense,” Women and Language19:2).

Use evidence

In the example above, the writers refer to several other sources when making their point. A literature review in this sense is just like any other academic research paper. Your interpretation of the available sources must be backed up with evidence to show that what you are saying is valid.

Be selective

Select only the most important points in each source to highlight in the review. The type of information you choose to mention should relate directly to the review’s focus, whether it is thematic, methodological, or chronological.

Use quotes sparingly

Falk and Mills do not use any direct quotes. That is because the survey nature of the literature review does not allow for in-depth discussion or detailed quotes from the text. Some short quotes here and there are okay, though, if you want to emphasize a point, or if what the author said just cannot be rewritten in your own words. Notice that Falk and Mills do quote certain terms that were coined by the author, not common knowledge, or taken directly from the study. But if you find yourself wanting to put in more quotes, check with your instructor.

Summarize and synthesize

Remember to summarize and synthesize your sources within each paragraph as well as throughout the review. The authors here recapitulate important features of Hamilton’s study, but then synthesize it by rephrasing the study’s significance and relating it to their own work.

Keep your own voice

While the literature review presents others’ ideas, your voice (the writer’s) should remain front and center. Notice that Falk and Mills weave references to other sources into their own text, but they still maintain their own voice by starting and ending the paragraph with their own ideas and their own words. The sources support what Falk and Mills are saying.

Use caution when paraphrasing

When paraphrasing a source that is not your own, be sure to represent the author’s information or opinions accurately and in your own words. In the preceding example, Falk and Mills either directly refer in the text to the author of their source, such as Hamilton, or they provide ample notation in the text when the ideas they are mentioning are not their own, for example, Gastil’s. For more information, please see our handout on plagiarism .

Revise, revise, revise

Draft in hand? Now you’re ready to revise. Spending a lot of time revising is a wise idea, because your main objective is to present the material, not the argument. So check over your review again to make sure it follows the assignment and/or your outline. Then, just as you would for most other academic forms of writing, rewrite or rework the language of your review so that you’ve presented your information in the most concise manner possible. Be sure to use terminology familiar to your audience; get rid of unnecessary jargon or slang. Finally, double check that you’ve documented your sources and formatted the review appropriately for your discipline. For tips on the revising and editing process, see our handout on revising drafts .

Works consulted

We consulted these works while writing this handout. This is not a comprehensive list of resources on the handout’s topic, and we encourage you to do your own research to find additional publications. Please do not use this list as a model for the format of your own reference list, as it may not match the citation style you are using. For guidance on formatting citations, please see the UNC Libraries citation tutorial . We revise these tips periodically and welcome feedback.

Anson, Chris M., and Robert A. Schwegler. 2010. The Longman Handbook for Writers and Readers , 6th ed. New York: Longman.

Jones, Robert, Patrick Bizzaro, and Cynthia Selfe. 1997. The Harcourt Brace Guide to Writing in the Disciplines . New York: Harcourt Brace.

Lamb, Sandra E. 1998. How to Write It: A Complete Guide to Everything You’ll Ever Write . Berkeley: Ten Speed Press.

Rosen, Leonard J., and Laurence Behrens. 2003. The Allyn & Bacon Handbook , 5th ed. New York: Longman.

Troyka, Lynn Quittman, and Doug Hesse. 2016. Simon and Schuster Handbook for Writers , 11th ed. London: Pearson.

You may reproduce it for non-commercial use if you use the entire handout and attribute the source: The Writing Center, University of North Carolina at Chapel Hill

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• What is a Literature Review? | Guide, Template, & Examples

What is a Literature Review? | Guide, Template, & Examples

Published on 22 February 2022 by Shona McCombes . Revised on 7 June 2022.

What is a literature review? A literature review is a survey of scholarly sources on a specific topic. It provides an overview of current knowledge, allowing you to identify relevant theories, methods, and gaps in the existing research.

There are five key steps to writing a literature review:

• Search for relevant literature
• Evaluate sources
• Identify themes, debates and gaps
• Outline the structure
• Write your literature review

A good literature review doesn’t just summarise sources – it analyses, synthesises, and critically evaluates to give a clear picture of the state of knowledge on the subject.

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Table of contents

Why write a literature review, examples of literature reviews, step 1: search for relevant literature, step 2: evaluate and select sources, step 3: identify themes, debates and gaps, step 4: outline your literature review’s structure, step 5: write your literature review, frequently asked questions about literature reviews, introduction.

• Quick Run-through
• Step 1 & 2

When you write a dissertation or thesis, you will have to conduct a literature review to situate your research within existing knowledge. The literature review gives you a chance to:

• Demonstrate your familiarity with the topic and scholarly context
• Develop a theoretical framework and methodology for your research
• Position yourself in relation to other researchers and theorists
• Show how your dissertation addresses a gap or contributes to a debate

You might also have to write a literature review as a stand-alone assignment. In this case, the purpose is to evaluate the current state of research and demonstrate your knowledge of scholarly debates around a topic.

The content will look slightly different in each case, but the process of conducting a literature review follows the same steps. We’ve written a step-by-step guide that you can follow below.

Prevent plagiarism, run a free check.

Writing literature reviews can be quite challenging! A good starting point could be to look at some examples, depending on what kind of literature review you’d like to write.

• Example literature review #1: “Why Do People Migrate? A Review of the Theoretical Literature” ( Theoretical literature review about the development of economic migration theory from the 1950s to today.)
• Example literature review #2: “Literature review as a research methodology: An overview and guidelines” ( Methodological literature review about interdisciplinary knowledge acquisition and production.)
• Example literature review #3: “The Use of Technology in English Language Learning: A Literature Review” ( Thematic literature review about the effects of technology on language acquisition.)
• Example literature review #4: “Learners’ Listening Comprehension Difficulties in English Language Learning: A Literature Review” ( Chronological literature review about how the concept of listening skills has changed over time.)

You can also check out our templates with literature review examples and sample outlines at the links below.

Download Word doc Download Google doc

Before you begin searching for literature, you need a clearly defined topic .

If you are writing the literature review section of a dissertation or research paper, you will search for literature related to your research objectives and questions .

If you are writing a literature review as a stand-alone assignment, you will have to choose a focus and develop a central question to direct your search. Unlike a dissertation research question, this question has to be answerable without collecting original data. You should be able to answer it based only on a review of existing publications.

Make a list of keywords

Start by creating a list of keywords related to your research topic. Include each of the key concepts or variables you’re interested in, and list any synonyms and related terms. You can add to this list if you discover new keywords in the process of your literature search.

• Social media, Facebook, Instagram, Twitter, Snapchat, TikTok
• Body image, self-perception, self-esteem, mental health
• Generation Z, teenagers, adolescents, youth

Search for relevant sources

Use your keywords to begin searching for sources. Some databases to search for journals and articles include:

• Your university’s library catalogue
• Google Scholar
• Project Muse (humanities and social sciences)
• Medline (life sciences and biomedicine)
• EconLit (economics)
• Inspec (physics, engineering and computer science)

You can use boolean operators to help narrow down your search:

Read the abstract to find out whether an article is relevant to your question. When you find a useful book or article, you can check the bibliography to find other relevant sources.

To identify the most important publications on your topic, take note of recurring citations. If the same authors, books or articles keep appearing in your reading, make sure to seek them out.

You probably won’t be able to read absolutely everything that has been written on the topic – you’ll have to evaluate which sources are most relevant to your questions.

For each publication, ask yourself:

• What question or problem is the author addressing?
• What are the key concepts and how are they defined?
• What are the key theories, models and methods? Does the research use established frameworks or take an innovative approach?
• What are the results and conclusions of the study?
• How does the publication relate to other literature in the field? Does it confirm, add to, or challenge established knowledge?
• How does the publication contribute to your understanding of the topic? What are its key insights and arguments?
• What are the strengths and weaknesses of the research?

Make sure the sources you use are credible, and make sure you read any landmark studies and major theories in your field of research.

You can find out how many times an article has been cited on Google Scholar – a high citation count means the article has been influential in the field, and should certainly be included in your literature review.

The scope of your review will depend on your topic and discipline: in the sciences you usually only review recent literature, but in the humanities you might take a long historical perspective (for example, to trace how a concept has changed in meaning over time).

Remember that you can use our template to summarise and evaluate sources you’re thinking about using!

Take notes and cite your sources

As you read, you should also begin the writing process. Take notes that you can later incorporate into the text of your literature review.

It’s important to keep track of your sources with references to avoid plagiarism . It can be helpful to make an annotated bibliography, where you compile full reference information and write a paragraph of summary and analysis for each source. This helps you remember what you read and saves time later in the process.

You can use our free APA Reference Generator for quick, correct, consistent citations.

To begin organising your literature review’s argument and structure, you need to understand the connections and relationships between the sources you’ve read. Based on your reading and notes, you can look for:

• Trends and patterns (in theory, method or results): do certain approaches become more or less popular over time?
• Themes: what questions or concepts recur across the literature?
• Debates, conflicts and contradictions: where do sources disagree?
• Pivotal publications: are there any influential theories or studies that changed the direction of the field?
• Gaps: what is missing from the literature? Are there weaknesses that need to be addressed?

This step will help you work out the structure of your literature review and (if applicable) show how your own research will contribute to existing knowledge.

• Most research has focused on young women.
• There is an increasing interest in the visual aspects of social media.
• But there is still a lack of robust research on highly-visual platforms like Instagram and Snapchat – this is a gap that you could address in your own research.

There are various approaches to organising the body of a literature review. You should have a rough idea of your strategy before you start writing.

Depending on the length of your literature review, you can combine several of these strategies (for example, your overall structure might be thematic, but each theme is discussed chronologically).

Chronological

The simplest approach is to trace the development of the topic over time. However, if you choose this strategy, be careful to avoid simply listing and summarising sources in order.

Try to analyse patterns, turning points and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred.

If you have found some recurring central themes, you can organise your literature review into subsections that address different aspects of the topic.

For example, if you are reviewing literature about inequalities in migrant health outcomes, key themes might include healthcare policy, language barriers, cultural attitudes, legal status, and economic access.

Methodological

If you draw your sources from different disciplines or fields that use a variety of research methods , you might want to compare the results and conclusions that emerge from different approaches. For example:

• Look at what results have emerged in qualitative versus quantitative research
• Discuss how the topic has been approached by empirical versus theoretical scholarship
• Divide the literature into sociological, historical, and cultural sources

Theoretical

A literature review is often the foundation for a theoretical framework . You can use it to discuss various theories, models, and definitions of key concepts.

You might argue for the relevance of a specific theoretical approach, or combine various theoretical concepts to create a framework for your research.

Like any other academic text, your literature review should have an introduction , a main body, and a conclusion . What you include in each depends on the objective of your literature review.

The introduction should clearly establish the focus and purpose of the literature review.

If you are writing the literature review as part of your dissertation or thesis, reiterate your central problem or research question and give a brief summary of the scholarly context. You can emphasise the timeliness of the topic (“many recent studies have focused on the problem of x”) or highlight a gap in the literature (“while there has been much research on x, few researchers have taken y into consideration”).

Depending on the length of your literature review, you might want to divide the body into subsections. You can use a subheading for each theme, time period, or methodological approach.

As you write, make sure to follow these tips:

• Summarise and synthesise: give an overview of the main points of each source and combine them into a coherent whole.
• Analyse and interpret: don’t just paraphrase other researchers – add your own interpretations, discussing the significance of findings in relation to the literature as a whole.
• Critically evaluate: mention the strengths and weaknesses of your sources.
• Write in well-structured paragraphs: use transitions and topic sentences to draw connections, comparisons and contrasts.

In the conclusion, you should summarise the key findings you have taken from the literature and emphasise their significance.

If the literature review is part of your dissertation or thesis, reiterate how your research addresses gaps and contributes new knowledge, or discuss how you have drawn on existing theories and methods to build a framework for your research. This can lead directly into your methodology section.

A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .

It is often written as part of a dissertation , thesis, research paper , or proposal .

There are several reasons to conduct a literature review at the beginning of a research project:

• To familiarise yourself with the current state of knowledge on your topic
• To ensure that you’re not just repeating what others have already done
• To identify gaps in knowledge and unresolved problems that your research can address
• To develop your theoretical framework and methodology
• To provide an overview of the key findings and debates on the topic

Writing the literature review shows your reader how your work relates to existing research and what new insights it will contribute.

The literature review usually comes near the beginning of your  dissertation . After the introduction , it grounds your research in a scholarly field and leads directly to your theoretical framework or methodology .

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The structure of a literature review

A literature review should be structured like any other essay: it should have an introduction, a middle or main body, and a conclusion.

Introduction

The introduction should:

• define your topic and provide an appropriate context for reviewing the literature;
• establish your reasons – i.e. point of view – for
• reviewing the literature;
• explain the organisation – i.e. sequence – of the review;
• state the scope of the review – i.e. what is included and what isn’t included. For example, if you were reviewing the literature on obesity in children you might say something like: There are a large number of studies of obesity trends in the general population. However, since the focus of this research is on obesity in children, these will not be reviewed in detail and will only be referred to as appropriate.

The middle or main body should:

• organise the literature according to common themes;
• provide insight into the relation between your chosen topic and the wider subject area e.g. between obesity in children and obesity in general;
• move from a general, wider view of the literature being reviewed to the specific focus of your research.

The conclusion should:

• summarise the important aspects of the existing body of literature;
• evaluate the current state of the literature reviewed;
• identify significant flaws or gaps in existing knowledge;
• outline areas for future study;
• link your research to existing knowledge.

Privacy Overview

• UConn Library
• Literature Review: The What, Why and How-to Guide
• Introduction

Literature Review: The What, Why and How-to Guide — Introduction

• Getting Started
• How to Pick a Topic
• Strategies to Find Sources
• Evaluating Sources & Lit. Reviews
• Tips for Writing Literature Reviews
• Writing Literature Review: Useful Sites
• Citation Resources
• Other Academic Writings

What are Literature Reviews?

So, what is a literature review? "A literature review is an account of what has been published on a topic by accredited scholars and researchers. In writing the literature review, your purpose is to convey to your reader what knowledge and ideas have been established on a topic, and what their strengths and weaknesses are. As a piece of writing, the literature review must be defined by a guiding concept (e.g., your research objective, the problem or issue you are discussing, or your argumentative thesis). It is not just a descriptive list of the material available, or a set of summaries." Taylor, D.  The literature review: A few tips on conducting it . University of Toronto Health Sciences Writing Centre.

Goals of Literature Reviews

What are the goals of creating a Literature Review?  A literature could be written to accomplish different aims:

• To develop a theory or evaluate an existing theory
• To summarize the historical or existing state of a research topic
• Identify a problem in a field of research 

Baumeister, R. F., & Leary, M. R. (1997). Writing narrative literature reviews .  Review of General Psychology , 1 (3), 311-320.

What kinds of sources require a Literature Review?

• A research paper assigned in a course
• A thesis or dissertation
• A grant proposal
• An article intended for publication in a journal

All these instances require you to collect what has been written about your research topic so that you can demonstrate how your own research sheds new light on the topic.

Types of Literature Reviews

What kinds of literature reviews are written?

Narrative review: The purpose of this type of review is to describe the current state of the research on a specific topic/research and to offer a critical analysis of the literature reviewed. Studies are grouped by research/theoretical categories, and themes and trends, strengths and weakness, and gaps are identified. The review ends with a conclusion section which summarizes the findings regarding the state of the research of the specific study, the gaps identify and if applicable, explains how the author's research will address gaps identify in the review and expand the knowledge on the topic reviewed.

• Example : Predictors and Outcomes of U.S. Quality Maternity Leave: A Review and Conceptual Framework:  10.1177/08948453211037398  

Systematic review : "The authors of a systematic review use a specific procedure to search the research literature, select the studies to include in their review, and critically evaluate the studies they find." (p. 139). Nelson, L. K. (2013). Research in Communication Sciences and Disorders . Plural Publishing.

• Example : The effect of leave policies on increasing fertility: a systematic review:  10.1057/s41599-022-01270-w

Meta-analysis : "Meta-analysis is a method of reviewing research findings in a quantitative fashion by transforming the data from individual studies into what is called an effect size and then pooling and analyzing this information. The basic goal in meta-analysis is to explain why different outcomes have occurred in different studies." (p. 197). Roberts, M. C., & Ilardi, S. S. (2003). Handbook of Research Methods in Clinical Psychology . Blackwell Publishing.

• Example : Employment Instability and Fertility in Europe: A Meta-Analysis:  10.1215/00703370-9164737

Meta-synthesis : "Qualitative meta-synthesis is a type of qualitative study that uses as data the findings from other qualitative studies linked by the same or related topic." (p.312). Zimmer, L. (2006). Qualitative meta-synthesis: A question of dialoguing with texts .  Journal of Advanced Nursing , 53 (3), 311-318.

• Example : Women’s perspectives on career successes and barriers: A qualitative meta-synthesis:  10.1177/05390184221113735

Literature Reviews in the Health Sciences

• UConn Health subject guide on systematic reviews Explanation of the different review types used in health sciences literature as well as tools to help you find the right review type
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Organizing Your Social Sciences Research Paper

• 5. The Literature Review
• Purpose of Guide
• Design Flaws to Avoid
• Independent and Dependent Variables
• Glossary of Research Terms
• Reading Research Effectively
• Narrowing a Topic Idea
• Broadening a Topic Idea
• Extending the Timeliness of a Topic Idea
• Academic Writing Style
• Choosing a Title
• Making an Outline
• Paragraph Development
• Research Process Video Series
• Executive Summary
• The C.A.R.S. Model
• Background Information
• The Research Problem/Question
• Theoretical Framework
• Citation Tracking
• Content Alert Services
• Evaluating Sources
• Primary Sources
• Secondary Sources
• Tiertiary Sources
• Scholarly vs. Popular Publications
• Qualitative Methods
• Quantitative Methods
• Insiderness
• Using Non-Textual Elements
• Limitations of the Study
• Common Grammar Mistakes
• Writing Concisely
• Avoiding Plagiarism
• Footnotes or Endnotes?
• Further Readings
• Generative AI and Writing
• USC Libraries Tutorials and Other Guides
• Bibliography

A literature review surveys prior research published in books, scholarly articles, and any other sources relevant to a particular issue, area of research, or theory, and by so doing, provides a description, summary, and critical evaluation of these works in relation to the research problem being investigated. Literature reviews are designed to provide an overview of sources you have used in researching a particular topic and to demonstrate to your readers how your research fits within existing scholarship about the topic.

Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper . Fourth edition. Thousand Oaks, CA: SAGE, 2014.

Importance of a Good Literature Review

A literature review may consist of simply a summary of key sources, but in the social sciences, a literature review usually has an organizational pattern and combines both summary and synthesis, often within specific conceptual categories . A summary is a recap of the important information of the source, but a synthesis is a re-organization, or a reshuffling, of that information in a way that informs how you are planning to investigate a research problem. The analytical features of a literature review might:

• Give a new interpretation of old material or combine new with old interpretations,
• Trace the intellectual progression of the field, including major debates,
• Depending on the situation, evaluate the sources and advise the reader on the most pertinent or relevant research, or
• Usually in the conclusion of a literature review, identify where gaps exist in how a problem has been researched to date.

Given this, the purpose of a literature review is to:

• Place each work in the context of its contribution to understanding the research problem being studied.
• Describe the relationship of each work to the others under consideration.
• Identify new ways to interpret prior research.
• Reveal any gaps that exist in the literature.
• Resolve conflicts amongst seemingly contradictory previous studies.
• Identify areas of prior scholarship to prevent duplication of effort.
• Point the way in fulfilling a need for additional research.
• Locate your own research within the context of existing literature [very important].

Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper. 2nd ed. Thousand Oaks, CA: Sage, 2005; Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1998; Jesson, Jill. Doing Your Literature Review: Traditional and Systematic Techniques . Los Angeles, CA: SAGE, 2011; Knopf, Jeffrey W. "Doing a Literature Review." PS: Political Science and Politics 39 (January 2006): 127-132; Ridley, Diana. The Literature Review: A Step-by-Step Guide for Students . 2nd ed. Los Angeles, CA: SAGE, 2012.

Types of Literature Reviews

It is important to think of knowledge in a given field as consisting of three layers. First, there are the primary studies that researchers conduct and publish. Second are the reviews of those studies that summarize and offer new interpretations built from and often extending beyond the primary studies. Third, there are the perceptions, conclusions, opinion, and interpretations that are shared informally among scholars that become part of the body of epistemological traditions within the field.

In composing a literature review, it is important to note that it is often this third layer of knowledge that is cited as "true" even though it often has only a loose relationship to the primary studies and secondary literature reviews. Given this, while literature reviews are designed to provide an overview and synthesis of pertinent sources you have explored, there are a number of approaches you could adopt depending upon the type of analysis underpinning your study.

Argumentative Review This form examines literature selectively in order to support or refute an argument, deeply embedded assumption, or philosophical problem already established in the literature. The purpose is to develop a body of literature that establishes a contrarian viewpoint. Given the value-laden nature of some social science research [e.g., educational reform; immigration control], argumentative approaches to analyzing the literature can be a legitimate and important form of discourse. However, note that they can also introduce problems of bias when they are used to make summary claims of the sort found in systematic reviews [see below].

Integrative Review Considered a form of research that reviews, critiques, and synthesizes representative literature on a topic in an integrated way such that new frameworks and perspectives on the topic are generated. The body of literature includes all studies that address related or identical hypotheses or research problems. A well-done integrative review meets the same standards as primary research in regard to clarity, rigor, and replication. This is the most common form of review in the social sciences.

Historical Review Few things rest in isolation from historical precedent. Historical literature reviews focus on examining research throughout a period of time, often starting with the first time an issue, concept, theory, phenomena emerged in the literature, then tracing its evolution within the scholarship of a discipline. The purpose is to place research in a historical context to show familiarity with state-of-the-art developments and to identify the likely directions for future research.

Methodological Review A review does not always focus on what someone said [findings], but how they came about saying what they say [method of analysis]. Reviewing methods of analysis provides a framework of understanding at different levels [i.e. those of theory, substantive fields, research approaches, and data collection and analysis techniques], how researchers draw upon a wide variety of knowledge ranging from the conceptual level to practical documents for use in fieldwork in the areas of ontological and epistemological consideration, quantitative and qualitative integration, sampling, interviewing, data collection, and data analysis. This approach helps highlight ethical issues which you should be aware of and consider as you go through your own study.

Systematic Review This form consists of an overview of existing evidence pertinent to a clearly formulated research question, which uses pre-specified and standardized methods to identify and critically appraise relevant research, and to collect, report, and analyze data from the studies that are included in the review. The goal is to deliberately document, critically evaluate, and summarize scientifically all of the research about a clearly defined research problem . Typically it focuses on a very specific empirical question, often posed in a cause-and-effect form, such as "To what extent does A contribute to B?" This type of literature review is primarily applied to examining prior research studies in clinical medicine and allied health fields, but it is increasingly being used in the social sciences.

Theoretical Review The purpose of this form is to examine the corpus of theory that has accumulated in regard to an issue, concept, theory, phenomena. The theoretical literature review helps to establish what theories already exist, the relationships between them, to what degree the existing theories have been investigated, and to develop new hypotheses to be tested. Often this form is used to help establish a lack of appropriate theories or reveal that current theories are inadequate for explaining new or emerging research problems. The unit of analysis can focus on a theoretical concept or a whole theory or framework.

NOTE : Most often the literature review will incorporate some combination of types. For example, a review that examines literature supporting or refuting an argument, assumption, or philosophical problem related to the research problem will also need to include writing supported by sources that establish the history of these arguments in the literature.

Baumeister, Roy F. and Mark R. Leary. "Writing Narrative Literature Reviews."  Review of General Psychology 1 (September 1997): 311-320; Mark R. Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper . 2nd ed. Thousand Oaks, CA: Sage, 2005; Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1998; Kennedy, Mary M. "Defining a Literature." Educational Researcher 36 (April 2007): 139-147; Petticrew, Mark and Helen Roberts. Systematic Reviews in the Social Sciences: A Practical Guide . Malden, MA: Blackwell Publishers, 2006; Torracro, Richard. "Writing Integrative Literature Reviews: Guidelines and Examples." Human Resource Development Review 4 (September 2005): 356-367; Rocco, Tonette S. and Maria S. Plakhotnik. "Literature Reviews, Conceptual Frameworks, and Theoretical Frameworks: Terms, Functions, and Distinctions." Human Ressource Development Review 8 (March 2008): 120-130; Sutton, Anthea. Systematic Approaches to a Successful Literature Review . Los Angeles, CA: Sage Publications, 2016.

Structure and Writing Style

I.  Thinking About Your Literature Review

The structure of a literature review should include the following in support of understanding the research problem :

• An overview of the subject, issue, or theory under consideration, along with the objectives of the literature review,
• Division of works under review into themes or categories [e.g. works that support a particular position, those against, and those offering alternative approaches entirely],
• An explanation of how each work is similar to and how it varies from the others,
• Conclusions as to which pieces are best considered in their argument, are most convincing of their opinions, and make the greatest contribution to the understanding and development of their area of research.

The critical evaluation of each work should consider :

• Provenance -- what are the author's credentials? Are the author's arguments supported by evidence [e.g. primary historical material, case studies, narratives, statistics, recent scientific findings]?
• Methodology -- were the techniques used to identify, gather, and analyze the data appropriate to addressing the research problem? Was the sample size appropriate? Were the results effectively interpreted and reported?
• Objectivity -- is the author's perspective even-handed or prejudicial? Is contrary data considered or is certain pertinent information ignored to prove the author's point?
• Persuasiveness -- which of the author's theses are most convincing or least convincing?
• Validity -- are the author's arguments and conclusions convincing? Does the work ultimately contribute in any significant way to an understanding of the subject?

II.  Development of the Literature Review

Four Basic Stages of Writing 1.  Problem formulation -- which topic or field is being examined and what are its component issues? 2.  Literature search -- finding materials relevant to the subject being explored. 3.  Data evaluation -- determining which literature makes a significant contribution to the understanding of the topic. 4.  Analysis and interpretation -- discussing the findings and conclusions of pertinent literature.

Consider the following issues before writing the literature review: Clarify If your assignment is not specific about what form your literature review should take, seek clarification from your professor by asking these questions: 1.  Roughly how many sources would be appropriate to include? 2.  What types of sources should I review (books, journal articles, websites; scholarly versus popular sources)? 3.  Should I summarize, synthesize, or critique sources by discussing a common theme or issue? 4.  Should I evaluate the sources in any way beyond evaluating how they relate to understanding the research problem? 5.  Should I provide subheadings and other background information, such as definitions and/or a history? Find Models Use the exercise of reviewing the literature to examine how authors in your discipline or area of interest have composed their literature review sections. Read them to get a sense of the types of themes you might want to look for in your own research or to identify ways to organize your final review. The bibliography or reference section of sources you've already read, such as required readings in the course syllabus, are also excellent entry points into your own research. Narrow the Topic The narrower your topic, the easier it will be to limit the number of sources you need to read in order to obtain a good survey of relevant resources. Your professor will probably not expect you to read everything that's available about the topic, but you'll make the act of reviewing easier if you first limit scope of the research problem. A good strategy is to begin by searching the USC Libraries Catalog for recent books about the topic and review the table of contents for chapters that focuses on specific issues. You can also review the indexes of books to find references to specific issues that can serve as the focus of your research. For example, a book surveying the history of the Israeli-Palestinian conflict may include a chapter on the role Egypt has played in mediating the conflict, or look in the index for the pages where Egypt is mentioned in the text. Consider Whether Your Sources are Current Some disciplines require that you use information that is as current as possible. This is particularly true in disciplines in medicine and the sciences where research conducted becomes obsolete very quickly as new discoveries are made. However, when writing a review in the social sciences, a survey of the history of the literature may be required. In other words, a complete understanding the research problem requires you to deliberately examine how knowledge and perspectives have changed over time. Sort through other current bibliographies or literature reviews in the field to get a sense of what your discipline expects. You can also use this method to explore what is considered by scholars to be a "hot topic" and what is not.

III.  Ways to Organize Your Literature Review

Chronology of Events If your review follows the chronological method, you could write about the materials according to when they were published. This approach should only be followed if a clear path of research building on previous research can be identified and that these trends follow a clear chronological order of development. For example, a literature review that focuses on continuing research about the emergence of German economic power after the fall of the Soviet Union. By Publication Order your sources by publication chronology, then, only if the order demonstrates a more important trend. For instance, you could order a review of literature on environmental studies of brown fields if the progression revealed, for example, a change in the soil collection practices of the researchers who wrote and/or conducted the studies. Thematic [“conceptual categories”] A thematic literature review is the most common approach to summarizing prior research in the social and behavioral sciences. Thematic reviews are organized around a topic or issue, rather than the progression of time, although the progression of time may still be incorporated into a thematic review. For example, a review of the Internet’s impact on American presidential politics could focus on the development of online political satire. While the study focuses on one topic, the Internet’s impact on American presidential politics, it would still be organized chronologically reflecting technological developments in media. The difference in this example between a "chronological" and a "thematic" approach is what is emphasized the most: themes related to the role of the Internet in presidential politics. Note that more authentic thematic reviews tend to break away from chronological order. A review organized in this manner would shift between time periods within each section according to the point being made. Methodological A methodological approach focuses on the methods utilized by the researcher. For the Internet in American presidential politics project, one methodological approach would be to look at cultural differences between the portrayal of American presidents on American, British, and French websites. Or the review might focus on the fundraising impact of the Internet on a particular political party. A methodological scope will influence either the types of documents in the review or the way in which these documents are discussed.

Other Sections of Your Literature Review Once you've decided on the organizational method for your literature review, the sections you need to include in the paper should be easy to figure out because they arise from your organizational strategy. In other words, a chronological review would have subsections for each vital time period; a thematic review would have subtopics based upon factors that relate to the theme or issue. However, sometimes you may need to add additional sections that are necessary for your study, but do not fit in the organizational strategy of the body. What other sections you include in the body is up to you. However, only include what is necessary for the reader to locate your study within the larger scholarship about the research problem.

Here are examples of other sections, usually in the form of a single paragraph, you may need to include depending on the type of review you write:

• Current Situation : Information necessary to understand the current topic or focus of the literature review.
• Sources Used : Describes the methods and resources [e.g., databases] you used to identify the literature you reviewed.
• History : The chronological progression of the field, the research literature, or an idea that is necessary to understand the literature review, if the body of the literature review is not already a chronology.
• Selection Methods : Criteria you used to select (and perhaps exclude) sources in your literature review. For instance, you might explain that your review includes only peer-reviewed [i.e., scholarly] sources.
• Standards : Description of the way in which you present your information.
• Questions for Further Research : What questions about the field has the review sparked? How will you further your research as a result of the review?

IV.  Writing Your Literature Review

Once you've settled on how to organize your literature review, you're ready to write each section. When writing your review, keep in mind these issues.

Use Evidence A literature review section is, in this sense, just like any other academic research paper. Your interpretation of the available sources must be backed up with evidence [citations] that demonstrates that what you are saying is valid. Be Selective Select only the most important points in each source to highlight in the review. The type of information you choose to mention should relate directly to the research problem, whether it is thematic, methodological, or chronological. Related items that provide additional information, but that are not key to understanding the research problem, can be included in a list of further readings . Use Quotes Sparingly Some short quotes are appropriate if you want to emphasize a point, or if what an author stated cannot be easily paraphrased. Sometimes you may need to quote certain terminology that was coined by the author, is not common knowledge, or taken directly from the study. Do not use extensive quotes as a substitute for using your own words in reviewing the literature. Summarize and Synthesize Remember to summarize and synthesize your sources within each thematic paragraph as well as throughout the review. Recapitulate important features of a research study, but then synthesize it by rephrasing the study's significance and relating it to your own work and the work of others. Keep Your Own Voice While the literature review presents others' ideas, your voice [the writer's] should remain front and center. For example, weave references to other sources into what you are writing but maintain your own voice by starting and ending the paragraph with your own ideas and wording. Use Caution When Paraphrasing When paraphrasing a source that is not your own, be sure to represent the author's information or opinions accurately and in your own words. Even when paraphrasing an author’s work, you still must provide a citation to that work.

V.  Common Mistakes to Avoid

These are the most common mistakes made in reviewing social science research literature.

• Sources in your literature review do not clearly relate to the research problem;
• You do not take sufficient time to define and identify the most relevant sources to use in the literature review related to the research problem;
• Relies exclusively on secondary analytical sources rather than including relevant primary research studies or data;
• Uncritically accepts another researcher's findings and interpretations as valid, rather than examining critically all aspects of the research design and analysis;
• Does not describe the search procedures that were used in identifying the literature to review;
• Reports isolated statistical results rather than synthesizing them in chi-squared or meta-analytic methods; and,
• Only includes research that validates assumptions and does not consider contrary findings and alternative interpretations found in the literature.

Cook, Kathleen E. and Elise Murowchick. “Do Literature Review Skills Transfer from One Course to Another?” Psychology Learning and Teaching 13 (March 2014): 3-11; Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper . 2nd ed. Thousand Oaks, CA: Sage, 2005; Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1998; Jesson, Jill. Doing Your Literature Review: Traditional and Systematic Techniques . London: SAGE, 2011; Literature Review Handout. Online Writing Center. Liberty University; Literature Reviews. The Writing Center. University of North Carolina; Onwuegbuzie, Anthony J. and Rebecca Frels. Seven Steps to a Comprehensive Literature Review: A Multimodal and Cultural Approach . Los Angeles, CA: SAGE, 2016; Ridley, Diana. The Literature Review: A Step-by-Step Guide for Students . 2nd ed. Los Angeles, CA: SAGE, 2012; Randolph, Justus J. “A Guide to Writing the Dissertation Literature Review." Practical Assessment, Research, and Evaluation. vol. 14, June 2009; Sutton, Anthea. Systematic Approaches to a Successful Literature Review . Los Angeles, CA: Sage Publications, 2016; Taylor, Dena. The Literature Review: A Few Tips On Conducting It. University College Writing Centre. University of Toronto; Writing a Literature Review. Academic Skills Centre. University of Canberra.

Writing Tip

Break Out of Your Disciplinary Box!

Thinking interdisciplinarily about a research problem can be a rewarding exercise in applying new ideas, theories, or concepts to an old problem. For example, what might cultural anthropologists say about the continuing conflict in the Middle East? In what ways might geographers view the need for better distribution of social service agencies in large cities than how social workers might study the issue? You don’t want to substitute a thorough review of core research literature in your discipline for studies conducted in other fields of study. However, particularly in the social sciences, thinking about research problems from multiple vectors is a key strategy for finding new solutions to a problem or gaining a new perspective. Consult with a librarian about identifying research databases in other disciplines; almost every field of study has at least one comprehensive database devoted to indexing its research literature.

Frodeman, Robert. The Oxford Handbook of Interdisciplinarity . New York: Oxford University Press, 2010.

Another Writing Tip

Don't Just Review for Content!

While conducting a review of the literature, maximize the time you devote to writing this part of your paper by thinking broadly about what you should be looking for and evaluating. Review not just what scholars are saying, but how are they saying it. Some questions to ask:

• How are they organizing their ideas?
• What methods have they used to study the problem?
• What theories have been used to explain, predict, or understand their research problem?
• What sources have they cited to support their conclusions?
• How have they used non-textual elements [e.g., charts, graphs, figures, etc.] to illustrate key points?

When you begin to write your literature review section, you'll be glad you dug deeper into how the research was designed and constructed because it establishes a means for developing more substantial analysis and interpretation of the research problem.

Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1 998.

Yet Another Writing Tip

When Do I Know I Can Stop Looking and Move On?

Here are several strategies you can utilize to assess whether you've thoroughly reviewed the literature:

• Look for repeating patterns in the research findings . If the same thing is being said, just by different people, then this likely demonstrates that the research problem has hit a conceptual dead end. At this point consider: Does your study extend current research?  Does it forge a new path? Or, does is merely add more of the same thing being said?
• Look at sources the authors cite to in their work . If you begin to see the same researchers cited again and again, then this is often an indication that no new ideas have been generated to address the research problem.
• Search Google Scholar to identify who has subsequently cited leading scholars already identified in your literature review [see next sub-tab]. This is called citation tracking and there are a number of sources that can help you identify who has cited whom, particularly scholars from outside of your discipline. Here again, if the same authors are being cited again and again, this may indicate no new literature has been written on the topic.

Onwuegbuzie, Anthony J. and Rebecca Frels. Seven Steps to a Comprehensive Literature Review: A Multimodal and Cultural Approach . Los Angeles, CA: Sage, 2016; Sutton, Anthea. Systematic Approaches to a Successful Literature Review . Los Angeles, CA: Sage Publications, 2016.

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What is a Literature Review? How to Write It (with Examples)

A literature review is a critical analysis and synthesis of existing research on a particular topic. It provides an overview of the current state of knowledge, identifies gaps, and highlights key findings in the literature. 1 The purpose of a literature review is to situate your own research within the context of existing scholarship, demonstrating your understanding of the topic and showing how your work contributes to the ongoing conversation in the field. Learning how to write a literature review is a critical tool for successful research. Your ability to summarize and synthesize prior research pertaining to a certain topic demonstrates your grasp on the topic of study, and assists in the learning process. 

Table of Contents

• What is the purpose of literature review? 
• a. Habitat Loss and Species Extinction: 
• b. Range Shifts and Phenological Changes: 
• c. Ocean Acidification and Coral Reefs: 
• d. Adaptive Strategies and Conservation Efforts: 
• How to write a good literature review 
• Choose a Topic and Define the Research Question: 
• Decide on the Scope of Your Review: 
• Select Databases for Searches: 
• Conduct Searches and Keep Track: 
• Review the Literature: 
• Organize and Write Your Literature Review: 
• Frequently asked questions 

What is a literature review?

A well-conducted literature review demonstrates the researcher’s familiarity with the existing literature, establishes the context for their own research, and contributes to scholarly conversations on the topic. One of the purposes of a literature review is also to help researchers avoid duplicating previous work and ensure that their research is informed by and builds upon the existing body of knowledge.

What is the purpose of literature review?

A literature review serves several important purposes within academic and research contexts. Here are some key objectives and functions of a literature review: 2  

• Contextualizing the Research Problem: The literature review provides a background and context for the research problem under investigation. It helps to situate the study within the existing body of knowledge. 
• Identifying Gaps in Knowledge: By identifying gaps, contradictions, or areas requiring further research, the researcher can shape the research question and justify the significance of the study. This is crucial for ensuring that the new research contributes something novel to the field. 
• Understanding Theoretical and Conceptual Frameworks: Literature reviews help researchers gain an understanding of the theoretical and conceptual frameworks used in previous studies. This aids in the development of a theoretical framework for the current research. 
• Providing Methodological Insights: Another purpose of literature reviews is that it allows researchers to learn about the methodologies employed in previous studies. This can help in choosing appropriate research methods for the current study and avoiding pitfalls that others may have encountered. 
• Establishing Credibility: A well-conducted literature review demonstrates the researcher’s familiarity with existing scholarship, establishing their credibility and expertise in the field. It also helps in building a solid foundation for the new research. 
• Informing Hypotheses or Research Questions: The literature review guides the formulation of hypotheses or research questions by highlighting relevant findings and areas of uncertainty in existing literature. 

Literature review example

Let’s delve deeper with a literature review example: Let’s say your literature review is about the impact of climate change on biodiversity. You might format your literature review into sections such as the effects of climate change on habitat loss and species extinction, phenological changes, and marine biodiversity. Each section would then summarize and analyze relevant studies in those areas, highlighting key findings and identifying gaps in the research. The review would conclude by emphasizing the need for further research on specific aspects of the relationship between climate change and biodiversity. The following literature review template provides a glimpse into the recommended literature review structure and content, demonstrating how research findings are organized around specific themes within a broader topic. 

Literature Review on Climate Change Impacts on Biodiversity:

Climate change is a global phenomenon with far-reaching consequences, including significant impacts on biodiversity. This literature review synthesizes key findings from various studies: 

a. Habitat Loss and Species Extinction:

Climate change-induced alterations in temperature and precipitation patterns contribute to habitat loss, affecting numerous species (Thomas et al., 2004). The review discusses how these changes increase the risk of extinction, particularly for species with specific habitat requirements. 

b. Range Shifts and Phenological Changes:

Observations of range shifts and changes in the timing of biological events (phenology) are documented in response to changing climatic conditions (Parmesan & Yohe, 2003). These shifts affect ecosystems and may lead to mismatches between species and their resources. 

c. Ocean Acidification and Coral Reefs:

The review explores the impact of climate change on marine biodiversity, emphasizing ocean acidification’s threat to coral reefs (Hoegh-Guldberg et al., 2007). Changes in pH levels negatively affect coral calcification, disrupting the delicate balance of marine ecosystems. 

d. Adaptive Strategies and Conservation Efforts:

Recognizing the urgency of the situation, the literature review discusses various adaptive strategies adopted by species and conservation efforts aimed at mitigating the impacts of climate change on biodiversity (Hannah et al., 2007). It emphasizes the importance of interdisciplinary approaches for effective conservation planning. 

How to write a good literature review

Writing a literature review involves summarizing and synthesizing existing research on a particular topic. A good literature review format should include the following elements. 

Introduction: The introduction sets the stage for your literature review, providing context and introducing the main focus of your review. 

• Opening Statement: Begin with a general statement about the broader topic and its significance in the field. 
• Scope and Purpose: Clearly define the scope of your literature review. Explain the specific research question or objective you aim to address. 
• Organizational Framework: Briefly outline the structure of your literature review, indicating how you will categorize and discuss the existing research. 
• Significance of the Study: Highlight why your literature review is important and how it contributes to the understanding of the chosen topic. 
• Thesis Statement: Conclude the introduction with a concise thesis statement that outlines the main argument or perspective you will develop in the body of the literature review. 

Body: The body of the literature review is where you provide a comprehensive analysis of existing literature, grouping studies based on themes, methodologies, or other relevant criteria. 

• Organize by Theme or Concept: Group studies that share common themes, concepts, or methodologies. Discuss each theme or concept in detail, summarizing key findings and identifying gaps or areas of disagreement. 
• Critical Analysis: Evaluate the strengths and weaknesses of each study. Discuss the methodologies used, the quality of evidence, and the overall contribution of each work to the understanding of the topic. 
• Synthesis of Findings: Synthesize the information from different studies to highlight trends, patterns, or areas of consensus in the literature. 
• Identification of Gaps: Discuss any gaps or limitations in the existing research and explain how your review contributes to filling these gaps. 
• Transition between Sections: Provide smooth transitions between different themes or concepts to maintain the flow of your literature review. 

Conclusion: The conclusion of your literature review should summarize the main findings, highlight the contributions of the review, and suggest avenues for future research. 

• Summary of Key Findings: Recap the main findings from the literature and restate how they contribute to your research question or objective. 
• Contributions to the Field: Discuss the overall contribution of your literature review to the existing knowledge in the field. 
• Implications and Applications: Explore the practical implications of the findings and suggest how they might impact future research or practice. 
• Recommendations for Future Research: Identify areas that require further investigation and propose potential directions for future research in the field. 
• Final Thoughts: Conclude with a final reflection on the importance of your literature review and its relevance to the broader academic community. 

Conducting a literature review

Conducting a literature review is an essential step in research that involves reviewing and analyzing existing literature on a specific topic. It’s important to know how to do a literature review effectively, so here are the steps to follow: 1  

Choose a Topic and Define the Research Question:

• Select a topic that is relevant to your field of study. 
• Clearly define your research question or objective. Determine what specific aspect of the topic do you want to explore? 

Decide on the Scope of Your Review:

• Determine the timeframe for your literature review. Are you focusing on recent developments, or do you want a historical overview? 
• Consider the geographical scope. Is your review global, or are you focusing on a specific region? 
• Define the inclusion and exclusion criteria. What types of sources will you include? Are there specific types of studies or publications you will exclude? 

Select Databases for Searches:

• Identify relevant databases for your field. Examples include PubMed, IEEE Xplore, Scopus, Web of Science, and Google Scholar. 
• Consider searching in library catalogs, institutional repositories, and specialized databases related to your topic. 

Conduct Searches and Keep Track:

• Develop a systematic search strategy using keywords, Boolean operators (AND, OR, NOT), and other search techniques. 
• Record and document your search strategy for transparency and replicability. 
• Keep track of the articles, including publication details, abstracts, and links. Use citation management tools like EndNote, Zotero, or Mendeley to organize your references. 

Review the Literature:

• Evaluate the relevance and quality of each source. Consider the methodology, sample size, and results of studies. 
• Organize the literature by themes or key concepts. Identify patterns, trends, and gaps in the existing research. 
• Summarize key findings and arguments from each source. Compare and contrast different perspectives. 
• Identify areas where there is a consensus in the literature and where there are conflicting opinions. 
• Provide critical analysis and synthesis of the literature. What are the strengths and weaknesses of existing research? 

Organize and Write Your Literature Review:

• Literature review outline should be based on themes, chronological order, or methodological approaches. 
• Write a clear and coherent narrative that synthesizes the information gathered. 
• Use proper citations for each source and ensure consistency in your citation style (APA, MLA, Chicago, etc.). 
• Conclude your literature review by summarizing key findings, identifying gaps, and suggesting areas for future research. 

The literature review sample and detailed advice on writing and conducting a review will help you produce a well-structured report. But remember that a literature review is an ongoing process, and it may be necessary to revisit and update it as your research progresses. 

Frequently asked questions

A literature review is a critical and comprehensive analysis of existing literature (published and unpublished works) on a specific topic or research question and provides a synthesis of the current state of knowledge in a particular field. A well-conducted literature review is crucial for researchers to build upon existing knowledge, avoid duplication of efforts, and contribute to the advancement of their field. It also helps researchers situate their work within a broader context and facilitates the development of a sound theoretical and conceptual framework for their studies.

Literature review is a crucial component of research writing, providing a solid background for a research paper’s investigation. The aim is to keep professionals up to date by providing an understanding of ongoing developments within a specific field, including research methods, and experimental techniques used in that field, and present that knowledge in the form of a written report. Also, the depth and breadth of the literature review emphasizes the credibility of the scholar in his or her field.  

Before writing a literature review, it’s essential to undertake several preparatory steps to ensure that your review is well-researched, organized, and focused. This includes choosing a topic of general interest to you and doing exploratory research on that topic, writing an annotated bibliography, and noting major points, especially those that relate to the position you have taken on the topic. 

Literature reviews and academic research papers are essential components of scholarly work but serve different purposes within the academic realm. 3 A literature review aims to provide a foundation for understanding the current state of research on a particular topic, identify gaps or controversies, and lay the groundwork for future research. Therefore, it draws heavily from existing academic sources, including books, journal articles, and other scholarly publications. In contrast, an academic research paper aims to present new knowledge, contribute to the academic discourse, and advance the understanding of a specific research question. Therefore, it involves a mix of existing literature (in the introduction and literature review sections) and original data or findings obtained through research methods. 

Literature reviews are essential components of academic and research papers, and various strategies can be employed to conduct them effectively. If you want to know how to write a literature review for a research paper, here are four common approaches that are often used by researchers.  Chronological Review: This strategy involves organizing the literature based on the chronological order of publication. It helps to trace the development of a topic over time, showing how ideas, theories, and research have evolved.  Thematic Review: Thematic reviews focus on identifying and analyzing themes or topics that cut across different studies. Instead of organizing the literature chronologically, it is grouped by key themes or concepts, allowing for a comprehensive exploration of various aspects of the topic.  Methodological Review: This strategy involves organizing the literature based on the research methods employed in different studies. It helps to highlight the strengths and weaknesses of various methodologies and allows the reader to evaluate the reliability and validity of the research findings.  Theoretical Review: A theoretical review examines the literature based on the theoretical frameworks used in different studies. This approach helps to identify the key theories that have been applied to the topic and assess their contributions to the understanding of the subject.  It’s important to note that these strategies are not mutually exclusive, and a literature review may combine elements of more than one approach. The choice of strategy depends on the research question, the nature of the literature available, and the goals of the review. Additionally, other strategies, such as integrative reviews or systematic reviews, may be employed depending on the specific requirements of the research.

The literature review format can vary depending on the specific publication guidelines. However, there are some common elements and structures that are often followed. Here is a general guideline for the format of a literature review:  Introduction:   Provide an overview of the topic.  Define the scope and purpose of the literature review.  State the research question or objective.  Body:   Organize the literature by themes, concepts, or chronology.  Critically analyze and evaluate each source.  Discuss the strengths and weaknesses of the studies.  Highlight any methodological limitations or biases.  Identify patterns, connections, or contradictions in the existing research.  Conclusion:   Summarize the key points discussed in the literature review.  Highlight the research gap.  Address the research question or objective stated in the introduction.  Highlight the contributions of the review and suggest directions for future research.

Both annotated bibliographies and literature reviews involve the examination of scholarly sources. While annotated bibliographies focus on individual sources with brief annotations, literature reviews provide a more in-depth, integrated, and comprehensive analysis of existing literature on a specific topic. The key differences are as follows: 

References 

• Denney, A. S., & Tewksbury, R. (2013). How to write a literature review.  Journal of criminal justice education ,  24 (2), 218-234. 
• Pan, M. L. (2016).  Preparing literature reviews: Qualitative and quantitative approaches . Taylor & Francis. 
• Cantero, C. (2019). How to write a literature review.  San José State University Writing Center . 

Paperpal is an AI writing assistant that help academics write better, faster with real-time suggestions for in-depth language and grammar correction. Trained on millions of research manuscripts enhanced by professional academic editors, Paperpal delivers human precision at machine speed.  

Try it for free or upgrade to  Paperpal Prime , which unlocks unlimited access to premium features like academic translation, paraphrasing, contextual synonyms, consistency checks and more. It’s like always having a professional academic editor by your side! Go beyond limitations and experience the future of academic writing.  Get Paperpal Prime now at just US$19 a month!

Related Reads:

• Empirical Research: A Comprehensive Guide for Academics 
• How to Write a Scientific Paper in 10 Steps 
• Life Sciences Papers: 9 Tips for Authors Writing in Biological Sciences
• What is an Argumentative Essay? How to Write It (With Examples)

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Ten Simple Rules for Writing a Literature Review

Marco pautasso.

1 Centre for Functional and Evolutionary Ecology (CEFE), CNRS, Montpellier, France

2 Centre for Biodiversity Synthesis and Analysis (CESAB), FRB, Aix-en-Provence, France

Literature reviews are in great demand in most scientific fields. Their need stems from the ever-increasing output of scientific publications [1] . For example, compared to 1991, in 2008 three, eight, and forty times more papers were indexed in Web of Science on malaria, obesity, and biodiversity, respectively [2] . Given such mountains of papers, scientists cannot be expected to examine in detail every single new paper relevant to their interests [3] . Thus, it is both advantageous and necessary to rely on regular summaries of the recent literature. Although recognition for scientists mainly comes from primary research, timely literature reviews can lead to new synthetic insights and are often widely read [4] . For such summaries to be useful, however, they need to be compiled in a professional way [5] .

When starting from scratch, reviewing the literature can require a titanic amount of work. That is why researchers who have spent their career working on a certain research issue are in a perfect position to review that literature. Some graduate schools are now offering courses in reviewing the literature, given that most research students start their project by producing an overview of what has already been done on their research issue [6] . However, it is likely that most scientists have not thought in detail about how to approach and carry out a literature review.

Reviewing the literature requires the ability to juggle multiple tasks, from finding and evaluating relevant material to synthesising information from various sources, from critical thinking to paraphrasing, evaluating, and citation skills [7] . In this contribution, I share ten simple rules I learned working on about 25 literature reviews as a PhD and postdoctoral student. Ideas and insights also come from discussions with coauthors and colleagues, as well as feedback from reviewers and editors.

Rule 1: Define a Topic and Audience

How to choose which topic to review? There are so many issues in contemporary science that you could spend a lifetime of attending conferences and reading the literature just pondering what to review. On the one hand, if you take several years to choose, several other people may have had the same idea in the meantime. On the other hand, only a well-considered topic is likely to lead to a brilliant literature review [8] . The topic must at least be:

• interesting to you (ideally, you should have come across a series of recent papers related to your line of work that call for a critical summary),
• an important aspect of the field (so that many readers will be interested in the review and there will be enough material to write it), and
• a well-defined issue (otherwise you could potentially include thousands of publications, which would make the review unhelpful).

Ideas for potential reviews may come from papers providing lists of key research questions to be answered [9] , but also from serendipitous moments during desultory reading and discussions. In addition to choosing your topic, you should also select a target audience. In many cases, the topic (e.g., web services in computational biology) will automatically define an audience (e.g., computational biologists), but that same topic may also be of interest to neighbouring fields (e.g., computer science, biology, etc.).

Rule 2: Search and Re-search the Literature

After having chosen your topic and audience, start by checking the literature and downloading relevant papers. Five pieces of advice here:

• keep track of the search items you use (so that your search can be replicated [10] ),
• keep a list of papers whose pdfs you cannot access immediately (so as to retrieve them later with alternative strategies),
• use a paper management system (e.g., Mendeley, Papers, Qiqqa, Sente),
• define early in the process some criteria for exclusion of irrelevant papers (these criteria can then be described in the review to help define its scope), and
• do not just look for research papers in the area you wish to review, but also seek previous reviews.

The chances are high that someone will already have published a literature review ( Figure 1 ), if not exactly on the issue you are planning to tackle, at least on a related topic. If there are already a few or several reviews of the literature on your issue, my advice is not to give up, but to carry on with your own literature review,

The bottom-right situation (many literature reviews but few research papers) is not just a theoretical situation; it applies, for example, to the study of the impacts of climate change on plant diseases, where there appear to be more literature reviews than research studies [33] .

• discussing in your review the approaches, limitations, and conclusions of past reviews,
• trying to find a new angle that has not been covered adequately in the previous reviews, and
• incorporating new material that has inevitably accumulated since their appearance.

When searching the literature for pertinent papers and reviews, the usual rules apply:

• be thorough,
• use different keywords and database sources (e.g., DBLP, Google Scholar, ISI Proceedings, JSTOR Search, Medline, Scopus, Web of Science), and
• look at who has cited past relevant papers and book chapters.

Rule 3: Take Notes While Reading

If you read the papers first, and only afterwards start writing the review, you will need a very good memory to remember who wrote what, and what your impressions and associations were while reading each single paper. My advice is, while reading, to start writing down interesting pieces of information, insights about how to organize the review, and thoughts on what to write. This way, by the time you have read the literature you selected, you will already have a rough draft of the review.

Of course, this draft will still need much rewriting, restructuring, and rethinking to obtain a text with a coherent argument [11] , but you will have avoided the danger posed by staring at a blank document. Be careful when taking notes to use quotation marks if you are provisionally copying verbatim from the literature. It is advisable then to reformulate such quotes with your own words in the final draft. It is important to be careful in noting the references already at this stage, so as to avoid misattributions. Using referencing software from the very beginning of your endeavour will save you time.

Rule 4: Choose the Type of Review You Wish to Write

After having taken notes while reading the literature, you will have a rough idea of the amount of material available for the review. This is probably a good time to decide whether to go for a mini- or a full review. Some journals are now favouring the publication of rather short reviews focusing on the last few years, with a limit on the number of words and citations. A mini-review is not necessarily a minor review: it may well attract more attention from busy readers, although it will inevitably simplify some issues and leave out some relevant material due to space limitations. A full review will have the advantage of more freedom to cover in detail the complexities of a particular scientific development, but may then be left in the pile of the very important papers “to be read” by readers with little time to spare for major monographs.

There is probably a continuum between mini- and full reviews. The same point applies to the dichotomy of descriptive vs. integrative reviews. While descriptive reviews focus on the methodology, findings, and interpretation of each reviewed study, integrative reviews attempt to find common ideas and concepts from the reviewed material [12] . A similar distinction exists between narrative and systematic reviews: while narrative reviews are qualitative, systematic reviews attempt to test a hypothesis based on the published evidence, which is gathered using a predefined protocol to reduce bias [13] , [14] . When systematic reviews analyse quantitative results in a quantitative way, they become meta-analyses. The choice between different review types will have to be made on a case-by-case basis, depending not just on the nature of the material found and the preferences of the target journal(s), but also on the time available to write the review and the number of coauthors [15] .

Rule 5: Keep the Review Focused, but Make It of Broad Interest

Whether your plan is to write a mini- or a full review, it is good advice to keep it focused 16 , 17 . Including material just for the sake of it can easily lead to reviews that are trying to do too many things at once. The need to keep a review focused can be problematic for interdisciplinary reviews, where the aim is to bridge the gap between fields [18] . If you are writing a review on, for example, how epidemiological approaches are used in modelling the spread of ideas, you may be inclined to include material from both parent fields, epidemiology and the study of cultural diffusion. This may be necessary to some extent, but in this case a focused review would only deal in detail with those studies at the interface between epidemiology and the spread of ideas.

While focus is an important feature of a successful review, this requirement has to be balanced with the need to make the review relevant to a broad audience. This square may be circled by discussing the wider implications of the reviewed topic for other disciplines.

Rule 6: Be Critical and Consistent

Reviewing the literature is not stamp collecting. A good review does not just summarize the literature, but discusses it critically, identifies methodological problems, and points out research gaps [19] . After having read a review of the literature, a reader should have a rough idea of:

• the major achievements in the reviewed field,
• the main areas of debate, and
• the outstanding research questions.

It is challenging to achieve a successful review on all these fronts. A solution can be to involve a set of complementary coauthors: some people are excellent at mapping what has been achieved, some others are very good at identifying dark clouds on the horizon, and some have instead a knack at predicting where solutions are going to come from. If your journal club has exactly this sort of team, then you should definitely write a review of the literature! In addition to critical thinking, a literature review needs consistency, for example in the choice of passive vs. active voice and present vs. past tense.

Rule 7: Find a Logical Structure

Like a well-baked cake, a good review has a number of telling features: it is worth the reader's time, timely, systematic, well written, focused, and critical. It also needs a good structure. With reviews, the usual subdivision of research papers into introduction, methods, results, and discussion does not work or is rarely used. However, a general introduction of the context and, toward the end, a recapitulation of the main points covered and take-home messages make sense also in the case of reviews. For systematic reviews, there is a trend towards including information about how the literature was searched (database, keywords, time limits) [20] .

How can you organize the flow of the main body of the review so that the reader will be drawn into and guided through it? It is generally helpful to draw a conceptual scheme of the review, e.g., with mind-mapping techniques. Such diagrams can help recognize a logical way to order and link the various sections of a review [21] . This is the case not just at the writing stage, but also for readers if the diagram is included in the review as a figure. A careful selection of diagrams and figures relevant to the reviewed topic can be very helpful to structure the text too [22] .

Rule 8: Make Use of Feedback

Reviews of the literature are normally peer-reviewed in the same way as research papers, and rightly so [23] . As a rule, incorporating feedback from reviewers greatly helps improve a review draft. Having read the review with a fresh mind, reviewers may spot inaccuracies, inconsistencies, and ambiguities that had not been noticed by the writers due to rereading the typescript too many times. It is however advisable to reread the draft one more time before submission, as a last-minute correction of typos, leaps, and muddled sentences may enable the reviewers to focus on providing advice on the content rather than the form.

Feedback is vital to writing a good review, and should be sought from a variety of colleagues, so as to obtain a diversity of views on the draft. This may lead in some cases to conflicting views on the merits of the paper, and on how to improve it, but such a situation is better than the absence of feedback. A diversity of feedback perspectives on a literature review can help identify where the consensus view stands in the landscape of the current scientific understanding of an issue [24] .

Rule 9: Include Your Own Relevant Research, but Be Objective

In many cases, reviewers of the literature will have published studies relevant to the review they are writing. This could create a conflict of interest: how can reviewers report objectively on their own work [25] ? Some scientists may be overly enthusiastic about what they have published, and thus risk giving too much importance to their own findings in the review. However, bias could also occur in the other direction: some scientists may be unduly dismissive of their own achievements, so that they will tend to downplay their contribution (if any) to a field when reviewing it.

In general, a review of the literature should neither be a public relations brochure nor an exercise in competitive self-denial. If a reviewer is up to the job of producing a well-organized and methodical review, which flows well and provides a service to the readership, then it should be possible to be objective in reviewing one's own relevant findings. In reviews written by multiple authors, this may be achieved by assigning the review of the results of a coauthor to different coauthors.

Rule 10: Be Up-to-Date, but Do Not Forget Older Studies

Given the progressive acceleration in the publication of scientific papers, today's reviews of the literature need awareness not just of the overall direction and achievements of a field of inquiry, but also of the latest studies, so as not to become out-of-date before they have been published. Ideally, a literature review should not identify as a major research gap an issue that has just been addressed in a series of papers in press (the same applies, of course, to older, overlooked studies (“sleeping beauties” [26] )). This implies that literature reviewers would do well to keep an eye on electronic lists of papers in press, given that it can take months before these appear in scientific databases. Some reviews declare that they have scanned the literature up to a certain point in time, but given that peer review can be a rather lengthy process, a full search for newly appeared literature at the revision stage may be worthwhile. Assessing the contribution of papers that have just appeared is particularly challenging, because there is little perspective with which to gauge their significance and impact on further research and society.

Inevitably, new papers on the reviewed topic (including independently written literature reviews) will appear from all quarters after the review has been published, so that there may soon be the need for an updated review. But this is the nature of science [27] – [32] . I wish everybody good luck with writing a review of the literature.

Acknowledgments

Many thanks to M. Barbosa, K. Dehnen-Schmutz, T. Döring, D. Fontaneto, M. Garbelotto, O. Holdenrieder, M. Jeger, D. Lonsdale, A. MacLeod, P. Mills, M. Moslonka-Lefebvre, G. Stancanelli, P. Weisberg, and X. Xu for insights and discussions, and to P. Bourne, T. Matoni, and D. Smith for helpful comments on a previous draft.

Funding Statement

This work was funded by the French Foundation for Research on Biodiversity (FRB) through its Centre for Synthesis and Analysis of Biodiversity data (CESAB), as part of the NETSEED research project. The funders had no role in the preparation of the manuscript.

What Is A Literature Review?

A plain-language explainer (with examples).

By:  Derek Jansen (MBA) & Kerryn Warren (PhD) | June 2020 (Updated May 2023)

If you’re faced with writing a dissertation or thesis, chances are you’ve encountered the term “literature review” . If you’re on this page, you’re probably not 100% what the literature review is all about. The good news is that you’ve come to the right place.

Literature Review 101

• What (exactly) is a literature review
• What’s the purpose of the literature review chapter
• How to find high-quality resources
• How to structure your literature review chapter
• Example of an actual literature review

What is a literature review?

The word “literature review” can refer to two related things that are part of the broader literature review process. The first is the task of  reviewing the literature  – i.e. sourcing and reading through the existing research relating to your research topic. The second is the  actual chapter  that you write up in your dissertation, thesis or research project. Let’s look at each of them:

Reviewing the literature

The first step of any literature review is to hunt down and  read through the existing research  that’s relevant to your research topic. To do this, you’ll use a combination of tools (we’ll discuss some of these later) to find journal articles, books, ebooks, research reports, dissertations, theses and any other credible sources of information that relate to your topic. You’ll then  summarise and catalogue these  for easy reference when you write up your literature review chapter. 

The literature review chapter

The second step of the literature review is to write the actual literature review chapter (this is usually the second chapter in a typical dissertation or thesis structure ). At the simplest level, the literature review chapter is an  overview of the key literature  that’s relevant to your research topic. This chapter should provide a smooth-flowing discussion of what research has already been done, what is known, what is unknown and what is contested in relation to your research topic. So, you can think of it as an  integrated review of the state of knowledge  around your research topic. 

What’s the purpose of a literature review?

The literature review chapter has a few important functions within your dissertation, thesis or research project. Let’s take a look at these:

Purpose #1 – Demonstrate your topic knowledge

The first function of the literature review chapter is, quite simply, to show the reader (or marker) that you  know what you’re talking about . In other words, a good literature review chapter demonstrates that you’ve read the relevant existing research and understand what’s going on – who’s said what, what’s agreed upon, disagreed upon and so on. This needs to be  more than just a summary  of who said what – it needs to integrate the existing research to  show how it all fits together  and what’s missing (which leads us to purpose #2, next). 

Purpose #2 – Reveal the research gap that you’ll fill

The second function of the literature review chapter is to  show what’s currently missing  from the existing research, to lay the foundation for your own research topic. In other words, your literature review chapter needs to show that there are currently “missing pieces” in terms of the bigger puzzle, and that  your study will fill one of those research gaps . By doing this, you are showing that your research topic is original and will help contribute to the body of knowledge. In other words, the literature review helps justify your research topic.  

Purpose #3 – Lay the foundation for your conceptual framework

The third function of the literature review is to form the  basis for a conceptual framework . Not every research topic will necessarily have a conceptual framework, but if your topic does require one, it needs to be rooted in your literature review. 

For example, let’s say your research aims to identify the drivers of a certain outcome – the factors which contribute to burnout in office workers. In this case, you’d likely develop a conceptual framework which details the potential factors (e.g. long hours, excessive stress, etc), as well as the outcome (burnout). Those factors would need to emerge from the literature review chapter – they can’t just come from your gut! 

So, in this case, the literature review chapter would uncover each of the potential factors (based on previous studies about burnout), which would then be modelled into a framework. 

Purpose #4 – To inform your methodology

The fourth function of the literature review is to  inform the choice of methodology  for your own research. As we’ve  discussed on the Grad Coach blog , your choice of methodology will be heavily influenced by your research aims, objectives and questions . Given that you’ll be reviewing studies covering a topic close to yours, it makes sense that you could learn a lot from their (well-considered) methodologies.

So, when you’re reviewing the literature, you’ll need to  pay close attention to the research design , methodology and methods used in similar studies, and use these to inform your methodology. Quite often, you’ll be able to  “borrow” from previous studies . This is especially true for quantitative studies , as you can use previously tried and tested measures and scales. 

How do I find articles for my literature review?

Finding quality journal articles is essential to crafting a rock-solid literature review. As you probably already know, not all research is created equally, and so you need to make sure that your literature review is  built on credible research . 

We could write an entire post on how to find quality literature (actually, we have ), but a good starting point is Google Scholar . Google Scholar is essentially the academic equivalent of Google, using Google’s powerful search capabilities to find relevant journal articles and reports. It certainly doesn’t cover every possible resource, but it’s a very useful way to get started on your literature review journey, as it will very quickly give you a good indication of what the  most popular pieces of research  are in your field.

One downside of Google Scholar is that it’s merely a search engine – that is, it lists the articles, but oftentimes  it doesn’t host the articles . So you’ll often hit a paywall when clicking through to journal websites. 

Thankfully, your university should provide you with access to their library, so you can find the article titles using Google Scholar and then search for them by name in your university’s online library. Your university may also provide you with access to  ResearchGate , which is another great source for existing research. 

Remember, the correct search keywords will be super important to get the right information from the start. So, pay close attention to the keywords used in the journal articles you read and use those keywords to search for more articles. If you can’t find a spoon in the kitchen, you haven’t looked in the right drawer. 

Need a helping hand?

How should I structure my literature review?

Unfortunately, there’s no generic universal answer for this one. The structure of your literature review will depend largely on your topic area and your research aims and objectives.

You could potentially structure your literature review chapter according to theme, group, variables , chronologically or per concepts in your field of research. We explain the main approaches to structuring your literature review here . You can also download a copy of our free literature review template to help you establish an initial structure.

In general, it’s also a good idea to start wide (i.e. the big-picture-level) and then narrow down, ending your literature review close to your research questions . However, there’s no universal one “right way” to structure your literature review. The most important thing is not to discuss your sources one after the other like a list – as we touched on earlier, your literature review needs to synthesise the research , not summarise it .

Ultimately, you need to craft your literature review so that it conveys the most important information effectively – it needs to tell a logical story in a digestible way. It’s no use starting off with highly technical terms and then only explaining what these terms mean later. Always assume your reader is not a subject matter expert and hold their hand through a journe y of the literature while keeping the functions of the literature review chapter (which we discussed earlier) front of mind.

Example of a literature review

In the video below, we walk you through a high-quality literature review from a dissertation that earned full distinction. This will give you a clearer view of what a strong literature review looks like in practice and hopefully provide some inspiration for your own. 

Wrapping Up

In this post, we’ve (hopefully) answered the question, “ what is a literature review? “. We’ve also considered the purpose and functions of the literature review, as well as how to find literature and how to structure the literature review chapter. If you’re keen to learn more, check out the literature review section of the Grad Coach blog , as well as our detailed video post covering how to write a literature review . 

Psst… there’s more!

This post is an extract from our bestselling Udemy Course, Literature Review Bootcamp . If you want to work smart, you don't want to miss this .

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16 Comments

Thanks for this review. It narrates what’s not been taught as tutors are always in a early to finish their classes.

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Timothy T. Chol [email protected]

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Well-presented overview of the literature!

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Literature Reviews

• What is a literature review?
• Steps in the Literature Review Process
• Define your research question
• Determine inclusion and exclusion criteria
• Choose databases and search
• Review Results
• Synthesize Results
• Analyze Results
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What is a Literature Review?

A literature or narrative review is a comprehensive review and analysis of the published literature on a specific topic or research question. The literature that is reviewed contains: books, articles, academic articles, conference proceedings, association papers, and dissertations. It contains the most pertinent studies and points to important past and current research and practices. It provides background and context, and shows how your research will contribute to the field. 

A literature review should: 

• Provide a comprehensive and updated review of the literature;
• Explain why this review has taken place;
• Articulate a position or hypothesis;
• Acknowledge and account for conflicting and corroborating points of view

From  S age Research Methods

Purpose of a Literature Review

A literature review can be written as an introduction to a study to:

• Demonstrate how a study fills a gap in research
• Compare a study with other research that's been done

Or it can be a separate work (a research article on its own) which:

• Organizes or describes a topic
• Describes variables within a particular issue/problem

Limitations of a Literature Review

Some of the limitations of a literature review are:

• It's a snapshot in time. Unlike other reviews, this one has beginning, a middle and an end. There may be future developments that could make your work less relevant.
• It may be too focused. Some niche studies may miss the bigger picture.
• It can be difficult to be comprehensive. There is no way to make sure all the literature on a topic was considered.
• It is easy to be biased if you stick to top tier journals. There may be other places where people are publishing exemplary research. Look to open access publications and conferences to reflect a more inclusive collection. Also, make sure to include opposing views (and not just supporting evidence).

Source: Grant, Maria J., and Andrew Booth. “A Typology of Reviews: An Analysis of 14 Review Types and Associated Methodologies.” Health Information & Libraries Journal, vol. 26, no. 2, June 2009, pp. 91–108. Wiley Online Library, doi:10.1111/j.1471-1842.2009.00848.x.

Meryl Brodsky : Communication and Information Studies

Hannah Chapman Tripp : Biology, Neuroscience

Carolyn Cunningham : Human Development & Family Sciences, Psychology, Sociology

Larayne Dallas : Engineering

Janelle Hedstrom : Special Education, Curriculum & Instruction, Ed Leadership & Policy ​

Susan Macicak : Linguistics

Imelda Vetter : Dell Medical School

For help in other subject areas, please see the guide to library specialists by subject .

Periodically, UT Libraries runs a workshop covering the basics and library support for literature reviews. While we try to offer these once per academic year, we find providing the recording to be helpful to community members who have missed the session. Following is the most recent recording of the workshop, Conducting a Literature Review. To view the recording, a UT login is required.

• October 26, 2022 recording
• Last Updated: Oct 26, 2022 2:49 PM
• URL: https://guides.lib.utexas.edu/literaturereviews

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Literature reviews, what is a literature review, learning more about how to do a literature review.

• Planning the Review
• The Research Question
• Choosing Where to Search
• Organizing the Review
• Writing the Review

A literature review is a review and synthesis of existing research on a topic or research question. A literature review is meant to analyze the scholarly literature, make connections across writings and identify strengths, weaknesses, trends, and missing conversations. A literature review should address different aspects of a topic as it relates to your research question. A literature review goes beyond a description or summary of the literature you have read. 

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Literature Review – Types Writing Guide and Examples

Table of Contents

Literature Review

Definition:

A literature review is a comprehensive and critical analysis of the existing literature on a particular topic or research question. It involves identifying, evaluating, and synthesizing relevant literature, including scholarly articles, books, and other sources, to provide a summary and critical assessment of what is known about the topic.

Types of Literature Review

Types of Literature Review are as follows:

• Narrative literature review : This type of review involves a comprehensive summary and critical analysis of the available literature on a particular topic or research question. It is often used as an introductory section of a research paper.
• Systematic literature review: This is a rigorous and structured review that follows a pre-defined protocol to identify, evaluate, and synthesize all relevant studies on a specific research question. It is often used in evidence-based practice and systematic reviews.
• Meta-analysis: This is a quantitative review that uses statistical methods to combine data from multiple studies to derive a summary effect size. It provides a more precise estimate of the overall effect than any individual study.
• Scoping review: This is a preliminary review that aims to map the existing literature on a broad topic area to identify research gaps and areas for further investigation.
• Critical literature review : This type of review evaluates the strengths and weaknesses of the existing literature on a particular topic or research question. It aims to provide a critical analysis of the literature and identify areas where further research is needed.
• Conceptual literature review: This review synthesizes and integrates theories and concepts from multiple sources to provide a new perspective on a particular topic. It aims to provide a theoretical framework for understanding a particular research question.
• Rapid literature review: This is a quick review that provides a snapshot of the current state of knowledge on a specific research question or topic. It is often used when time and resources are limited.
• Thematic literature review : This review identifies and analyzes common themes and patterns across a body of literature on a particular topic. It aims to provide a comprehensive overview of the literature and identify key themes and concepts.
• Realist literature review: This review is often used in social science research and aims to identify how and why certain interventions work in certain contexts. It takes into account the context and complexities of real-world situations.
• State-of-the-art literature review : This type of review provides an overview of the current state of knowledge in a particular field, highlighting the most recent and relevant research. It is often used in fields where knowledge is rapidly evolving, such as technology or medicine.
• Integrative literature review: This type of review synthesizes and integrates findings from multiple studies on a particular topic to identify patterns, themes, and gaps in the literature. It aims to provide a comprehensive understanding of the current state of knowledge on a particular topic.
• Umbrella literature review : This review is used to provide a broad overview of a large and diverse body of literature on a particular topic. It aims to identify common themes and patterns across different areas of research.
• Historical literature review: This type of review examines the historical development of research on a particular topic or research question. It aims to provide a historical context for understanding the current state of knowledge on a particular topic.
• Problem-oriented literature review : This review focuses on a specific problem or issue and examines the literature to identify potential solutions or interventions. It aims to provide practical recommendations for addressing a particular problem or issue.
• Mixed-methods literature review : This type of review combines quantitative and qualitative methods to synthesize and analyze the available literature on a particular topic. It aims to provide a more comprehensive understanding of the research question by combining different types of evidence.

Parts of Literature Review

Parts of a literature review are as follows:

Introduction

The introduction of a literature review typically provides background information on the research topic and why it is important. It outlines the objectives of the review, the research question or hypothesis, and the scope of the review.

Literature Search

This section outlines the search strategy and databases used to identify relevant literature. The search terms used, inclusion and exclusion criteria, and any limitations of the search are described.

Literature Analysis

The literature analysis is the main body of the literature review. This section summarizes and synthesizes the literature that is relevant to the research question or hypothesis. The review should be organized thematically, chronologically, or by methodology, depending on the research objectives.

Critical Evaluation

Critical evaluation involves assessing the quality and validity of the literature. This includes evaluating the reliability and validity of the studies reviewed, the methodology used, and the strength of the evidence.

The conclusion of the literature review should summarize the main findings, identify any gaps in the literature, and suggest areas for future research. It should also reiterate the importance of the research question or hypothesis and the contribution of the literature review to the overall research project.

The references list includes all the sources cited in the literature review, and follows a specific referencing style (e.g., APA, MLA, Harvard).

How to write Literature Review

Here are some steps to follow when writing a literature review:

• Define your research question or topic : Before starting your literature review, it is essential to define your research question or topic. This will help you identify relevant literature and determine the scope of your review.
• Conduct a comprehensive search: Use databases and search engines to find relevant literature. Look for peer-reviewed articles, books, and other academic sources that are relevant to your research question or topic.
• Evaluate the sources: Once you have found potential sources, evaluate them critically to determine their relevance, credibility, and quality. Look for recent publications, reputable authors, and reliable sources of data and evidence.
• Organize your sources: Group the sources by theme, method, or research question. This will help you identify similarities and differences among the literature, and provide a structure for your literature review.
• Analyze and synthesize the literature : Analyze each source in depth, identifying the key findings, methodologies, and conclusions. Then, synthesize the information from the sources, identifying patterns and themes in the literature.
• Write the literature review : Start with an introduction that provides an overview of the topic and the purpose of the literature review. Then, organize the literature according to your chosen structure, and analyze and synthesize the sources. Finally, provide a conclusion that summarizes the key findings of the literature review, identifies gaps in knowledge, and suggests areas for future research.
• Edit and proofread: Once you have written your literature review, edit and proofread it carefully to ensure that it is well-organized, clear, and concise.

Examples of Literature Review

Here’s an example of how a literature review can be conducted for a thesis on the topic of “ The Impact of Social Media on Teenagers’ Mental Health”:

• Start by identifying the key terms related to your research topic. In this case, the key terms are “social media,” “teenagers,” and “mental health.”
• Use academic databases like Google Scholar, JSTOR, or PubMed to search for relevant articles, books, and other publications. Use these keywords in your search to narrow down your results.
• Evaluate the sources you find to determine if they are relevant to your research question. You may want to consider the publication date, author’s credentials, and the journal or book publisher.
• Begin reading and taking notes on each source, paying attention to key findings, methodologies used, and any gaps in the research.
• Organize your findings into themes or categories. For example, you might categorize your sources into those that examine the impact of social media on self-esteem, those that explore the effects of cyberbullying, and those that investigate the relationship between social media use and depression.
• Synthesize your findings by summarizing the key themes and highlighting any gaps or inconsistencies in the research. Identify areas where further research is needed.
• Use your literature review to inform your research questions and hypotheses for your thesis.

For example, after conducting a literature review on the impact of social media on teenagers’ mental health, a thesis might look like this:

“Using a mixed-methods approach, this study aims to investigate the relationship between social media use and mental health outcomes in teenagers. Specifically, the study will examine the effects of cyberbullying, social comparison, and excessive social media use on self-esteem, anxiety, and depression. Through an analysis of survey data and qualitative interviews with teenagers, the study will provide insight into the complex relationship between social media use and mental health outcomes, and identify strategies for promoting positive mental health outcomes in young people.”

Reference: Smith, J., Jones, M., & Lee, S. (2019). The effects of social media use on adolescent mental health: A systematic review. Journal of Adolescent Health, 65(2), 154-165. doi:10.1016/j.jadohealth.2019.03.024

Reference Example: Author, A. A., Author, B. B., & Author, C. C. (Year). Title of article. Title of Journal, volume number(issue number), page range. doi:0000000/000000000000 or URL

Applications of Literature Review

some applications of literature review in different fields:

• Social Sciences: In social sciences, literature reviews are used to identify gaps in existing research, to develop research questions, and to provide a theoretical framework for research. Literature reviews are commonly used in fields such as sociology, psychology, anthropology, and political science.
• Natural Sciences: In natural sciences, literature reviews are used to summarize and evaluate the current state of knowledge in a particular field or subfield. Literature reviews can help researchers identify areas where more research is needed and provide insights into the latest developments in a particular field. Fields such as biology, chemistry, and physics commonly use literature reviews.
• Health Sciences: In health sciences, literature reviews are used to evaluate the effectiveness of treatments, identify best practices, and determine areas where more research is needed. Literature reviews are commonly used in fields such as medicine, nursing, and public health.
• Humanities: In humanities, literature reviews are used to identify gaps in existing knowledge, develop new interpretations of texts or cultural artifacts, and provide a theoretical framework for research. Literature reviews are commonly used in fields such as history, literary studies, and philosophy.

Role of Literature Review in Research

Here are some applications of literature review in research:

• Identifying Research Gaps : Literature review helps researchers identify gaps in existing research and literature related to their research question. This allows them to develop new research questions and hypotheses to fill those gaps.
• Developing Theoretical Framework: Literature review helps researchers develop a theoretical framework for their research. By analyzing and synthesizing existing literature, researchers can identify the key concepts, theories, and models that are relevant to their research.
• Selecting Research Methods : Literature review helps researchers select appropriate research methods and techniques based on previous research. It also helps researchers to identify potential biases or limitations of certain methods and techniques.
• Data Collection and Analysis: Literature review helps researchers in data collection and analysis by providing a foundation for the development of data collection instruments and methods. It also helps researchers to identify relevant data sources and identify potential data analysis techniques.
• Communicating Results: Literature review helps researchers to communicate their results effectively by providing a context for their research. It also helps to justify the significance of their findings in relation to existing research and literature.

Purpose of Literature Review

Some of the specific purposes of a literature review are as follows:

• To provide context: A literature review helps to provide context for your research by situating it within the broader body of literature on the topic.
• To identify gaps and inconsistencies: A literature review helps to identify areas where further research is needed or where there are inconsistencies in the existing literature.
• To synthesize information: A literature review helps to synthesize the information from multiple sources and present a coherent and comprehensive picture of the current state of knowledge on the topic.
• To identify key concepts and theories : A literature review helps to identify key concepts and theories that are relevant to your research question and provide a theoretical framework for your study.
• To inform research design: A literature review can inform the design of your research study by identifying appropriate research methods, data sources, and research questions.

Characteristics of Literature Review

Some Characteristics of Literature Review are as follows:

• Identifying gaps in knowledge: A literature review helps to identify gaps in the existing knowledge and research on a specific topic or research question. By analyzing and synthesizing the literature, you can identify areas where further research is needed and where new insights can be gained.
• Establishing the significance of your research: A literature review helps to establish the significance of your own research by placing it in the context of existing research. By demonstrating the relevance of your research to the existing literature, you can establish its importance and value.
• Informing research design and methodology : A literature review helps to inform research design and methodology by identifying the most appropriate research methods, techniques, and instruments. By reviewing the literature, you can identify the strengths and limitations of different research methods and techniques, and select the most appropriate ones for your own research.
• Supporting arguments and claims: A literature review provides evidence to support arguments and claims made in academic writing. By citing and analyzing the literature, you can provide a solid foundation for your own arguments and claims.
• I dentifying potential collaborators and mentors: A literature review can help identify potential collaborators and mentors by identifying researchers and practitioners who are working on related topics or using similar methods. By building relationships with these individuals, you can gain valuable insights and support for your own research and practice.
• Keeping up-to-date with the latest research : A literature review helps to keep you up-to-date with the latest research on a specific topic or research question. By regularly reviewing the literature, you can stay informed about the latest findings and developments in your field.

Advantages of Literature Review

There are several advantages to conducting a literature review as part of a research project, including:

• Establishing the significance of the research : A literature review helps to establish the significance of the research by demonstrating the gap or problem in the existing literature that the study aims to address.
• Identifying key concepts and theories: A literature review can help to identify key concepts and theories that are relevant to the research question, and provide a theoretical framework for the study.
• Supporting the research methodology : A literature review can inform the research methodology by identifying appropriate research methods, data sources, and research questions.
• Providing a comprehensive overview of the literature : A literature review provides a comprehensive overview of the current state of knowledge on a topic, allowing the researcher to identify key themes, debates, and areas of agreement or disagreement.
• Identifying potential research questions: A literature review can help to identify potential research questions and areas for further investigation.
• Avoiding duplication of research: A literature review can help to avoid duplication of research by identifying what has already been done on a topic, and what remains to be done.
• Enhancing the credibility of the research : A literature review helps to enhance the credibility of the research by demonstrating the researcher’s knowledge of the existing literature and their ability to situate their research within a broader context.

Limitations of Literature Review

Limitations of Literature Review are as follows:

• Limited scope : Literature reviews can only cover the existing literature on a particular topic, which may be limited in scope or depth.
• Publication bias : Literature reviews may be influenced by publication bias, which occurs when researchers are more likely to publish positive results than negative ones. This can lead to an incomplete or biased picture of the literature.
• Quality of sources : The quality of the literature reviewed can vary widely, and not all sources may be reliable or valid.
• Time-limited: Literature reviews can become quickly outdated as new research is published, making it difficult to keep up with the latest developments in a field.
• Subjective interpretation : Literature reviews can be subjective, and the interpretation of the findings can vary depending on the researcher’s perspective or bias.
• Lack of original data : Literature reviews do not generate new data, but rather rely on the analysis of existing studies.
• Risk of plagiarism: It is important to ensure that literature reviews do not inadvertently contain plagiarism, which can occur when researchers use the work of others without proper attribution.

About the author

Muhammad Hassan

Researcher, Academic Writer, Web developer

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How do I Write a Literature Review?: #5 Writing the Review

• Step #1: Choosing a Topic
• Step #2: Finding Information
• Step #3: Evaluating Content
• Step #4: Synthesizing Content
• #5 Writing the Review
• Citing Your Sources

WRITING THE REVIEW 

You've done the research and now you're ready to put your findings down on paper. When preparing to write your review, first consider how will you organize your review.

The actual review generally has 5 components:

Abstract  -  An abstract is a summary of your literature review. It is made up of the following parts:

• A contextual sentence about your motivation behind your research topic
• Your thesis statement
• A descriptive statement about the types of literature used in the review
• Summarize your findings
• Conclusion(s) based upon your findings

Introduction :   Like a typical research paper introduction, provide the reader with a quick idea of the topic of the literature review:

• Define or identify the general topic, issue, or area of concern. This provides the reader with context for reviewing the literature.
• Identify related trends in what has already been published about the topic; or conflicts in theory, methodology, evidence, and conclusions; or gaps in research and scholarship; or a single problem or new perspective of immediate interest.
• Establish your reason (point of view) for reviewing the literature; explain the criteria to be used in analyzing and comparing literature and the organization of the review (sequence); and, when necessary, state why certain literature is or is not included (scope)  - 

Body :  The body of a literature review contains your discussion of sources and can be organized in 3 ways-

• Chronological -  by publication or by trend
• Thematic -  organized around a topic or issue, rather than the progression of time
• Methodical -  the focusing factor usually does not have to do with the content of the material. Instead, it focuses on the "methods" of the literature's researcher or writer that you are reviewing

You may also want to include a section on "questions for further research" and discuss what questions the review has sparked about the topic/field or offer suggestions for future studies/examinations that build on your current findings.

Conclusion :  In the conclusion, you should:

Conclude your paper by providing your reader with some perspective on the relationship between your literature review's specific topic and how it's related to it's parent discipline, scientific endeavor, or profession.

Bibliography :   Since a literature review is composed of pieces of research, it is very important that your correctly cite the literature you are reviewing, both in the reviews body as well as in a bibliography/works cited. To learn more about different citation styles, visit the " Citing Your Sources " tab.

• Writing a Literature Review: Wesleyan University
• Literature Review: Edith Cowan University
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• URL: https://libguides.eastern.edu/literature_reviews

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Introduction

• About Case Study Reports
• Section A: Overview
• Section B: Planning and Researching
• Section C: Parts of a Case Study
• Section D: Reviewing and Presenting
• Section E: Revising Your Work
• Section F: Resources
• Your Workspace
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• About Lab Reports
• Section C: Critical Features
• Section D: Parts of a Lab Report

• About Literature Review

Section C: Parts of a Literature Review

• Section D: Critical Writing Skills

• About Reflective Writing
• Section B: How Can I Reflect?
• Section C: How Do I Get Started?
• Section D: Writing a Reflection

Literature Review Prepared by University of Waterloo

This section closely examines and discusses the parts of a literature review in addition to readers' expectations.

What will I learn?

By the end of this section, you will be able to

• understand the purpose and features of each part of a literature review,
• identify and analyze the necessary information to include within each section, and
• use the Review Matrix to help you write a literature review.

Prepared by

What is the Purpose of an Introduction?

The introduction moves from general to more specific background information, giving readers contextual knowledge on your topic. The introduction states the scope of your literature review, includes your thesis, gives your objective, tells readers how the review is organized, and situates your work in the existing scholarly conversation.

What should be Included in an Introduction?

Use the following questions as a guide to write your introduction:

Guiding Questions

• What context or background information do readers need to know in order to understand the conversation between scholars and your analysis of it?
• In what ways is the research area important, interesting, problematic, or relevant?
• What do we not know about how the topic has been approached or applied?
• From what scholarly perspective has this topic been viewed? How can it be viewed differently?

Tips and Strategies

• Avoid providing too many details for background information.
• State the problem as specifically and clearly as possible.
• Highlight significance or importance of the topic.
• What is the purpose of your literature review?
• Can you turn your research question into a statement?
• Avoid rhetorical questions.
• Make sure your objective is consistent with your scope.
• How did you find your articles for review?
• What were your inclusion criteria?
• Were the studies you consulted limited by publication year, methodology, geographic area of publication or focus, theoretical framework, author perspective, or subtopic?
• Can you justify deliberately excluding works that address your topic in some way?
• Most topics have the potential to be quite large. How will you limit important components that comprise your topic (Figure C.1) and how much detail will you devote to each of these aspects (Figure C.2)?

Figure C.1 : Choose your scope

Choose sources that are related to your topic, but that also fall within your selection criteria. This may mean excluding sources that are only somewhat related to your topic in favour of sources that better fit within your search parameters. © University of Waterloo

Figure C.2 : Choose your level of detail

Some elements of your topic will require more investigation than others. Determine how much detail and depth each component of your literature review will require. For instance, is a wide perspective sufficient to give an overview of the scholarly discussion on your topic, or do you need to focus on complex details of small sections of your topic? Not all sections of your literature review will require the same level of detail, so choose your approach accordingly. © University of Waterloo and NASA

• What is your principal finding?
• What is the value of your finding?
• What is the answer to your research question?
• Have you explained your thesis statement beyond simply stating a fact?
• Has your thesis statement addressed 'how' and 'why' questions?
• State your thesis clearly.
• Your thesis needs to answer your research question, not simply reiterate your research question as a statement.
• Have a working thesis before starting to write your literature review, but know that you will most likely refine it while writing because your ideas will become clearer as you explain your analysis.
• Use words like 'because,' 'through,' 'by,' or 'due to' and answer 'how' and 'why' questions to extend your thesis statement.
• How is your literature review structured?
• What sections are in your literature review?
• Outline the order of sections in your literature review.
• Use signal words to explain the relationship between those sections.

Body Paragraphs

What are the purposes of body paragraphs.

Body paragraphs work together to logically discuss your synthesis and analysis of sources. The body paragraphs support your thesis and present your overall conclusions about your research.

What should be included in Body Paragraphs?

Clear organization.

• Paraphrasing
• Does your organization method match the purpose of your literature review?
• Can your material be arranged chronologically, thematically, or along lines of debate?
• Does the placement of each paragraph contribute to your literature review's logic and clarity?
• Do your paragraphs work together to create a cohesive argument?

Tips and strategies

• Decide on an organization method and stick with it.
• Use clear topic sentences.
• Sequence body paragraphs in a logical way.
• Use reverse outlining techniques to ensure your body paragraphs not only fit together, but also collectively integrate your research and findings.
• Do your headings match the content of your body paragraphs?
• Are your headings succinct?
• Do you have enough content to warrant a heading?
• Does the order of your headings contribute to the overall logic of your literature review?
• Make sure you have more than one heading if you plan on using headings at all.
• Write your headings as a phrase instead of as an independent clause .
• Avoid wordiness while crafting your heading.
• Refer to your style guide for formatting requirements, such as bolding, capitalizing, and italicizing.

Effective Body Paragraphing

• Does your paragraph have a topic sentence?
• Do you include supporting evidence?
• Do you analyze and discuss your evidence?
• Do your paragraphs concentrate on only one point each?
• Does any information belong in other paragraphs?
• Avoid repetition and redundancy within your paragraphs. Aim to extend and explain rather than to restate.
• Your topic sentence should make a claim that contributes to your thesis statement.
• Vary the stylistic construction of your topic sentences. For example, if your previous paragraph began with "Researchers have found...," then your next paragraph should not begin with that same phrase.
• Use precise words in your topic sentence.*

*Using precise words in your topic sentence

• NO: There are several studies that address this problem.
• YES: Several studies address the problem of storing solar power.
• NO: He later restructured these studies to incorporate Fry's theorem.
• YES: Young incorporated Fry's theorem into his later studies , from 1999 to 2005.

Evidence from Sources

• Does your paragraph contain sufficient evidence to support your claim?
• Do you explain how your evidence supports your claim?
• Is the amount of evidence you incorporate appropriate to the amount of analysis you provide?
• Have you used evidence and analysis from your Matrix?
• Does your evidence fit with the content of your paragraph while also building your argument?
• Avoid listing facts without explaining them.
• Balance your analysis with your evidence.
• Avoid relying too heavily on a limited number of sources.
• Rather than treating a source individually, treat it in relation to other sources.
• Place your evidence so that it displays a logical progression.

Paraphrase, Quotation, and Summary

• Have you selected the appropriate method to integrate evidence (i.e., paraphrase, quotation, summary)?
• Have you properly cited your paraphrase, quotation, or summary?
• Have you used proper punctuation to integrate your quotations?
• Does your quotation, paraphrase, or summary grammatically fit within your sentence?
• Have you accurately represented ideas that you are paraphrasing or summarizing?
• Have you treated your quotations, paraphrases, or summaries with academic integrity ?
• Have you introduced your paraphrase, summary, or quotation to the reader using signal words?
• Input citation information as you write to not lose track of sources.
• Use verb tenses to contextualize your evidence and analysis ( past vs. present vs. present perfect ).
• Consult your style guide for quotation and citation formatting.
• Revisit the purpose of your literature review while deciding when to paraphrase, summarize, or quote.
• Read sentences that contain quoted material out loud. If the sentence is awkward, adjust the punctuation and grammar to better integrate the material.

Example Body Paragraph

Click through the numbers below to see how the various components of a paragraph function and work together.

While there is little doubt that extracurricular opportunities at U of W are a positive and critical component of students' overall development, providing students with time management skills is equally important. One only needs to look at past alumni to see the validity of this claim. As famous alum, Harry Wright states: "I sometimes overdid it with extracurricular activities when I was at U of W, missing out on valuable academic opportunities. Fortunately, I buckled down in my senior year and managed a "C" average, and things have worked out fine since" (Paige 227). In this example, Harry Wright is arguing that the detrimental effects of excessive extracurricular involvement can be rectified in the senior year of university. Even though Harry Wright is certainly correct when he implies that it is never too late for students to try to raise their GPA, it is probably better for students to attempt to balance academic and other activities early in their university career. Also, Wright assumes that all students can achieve what they want with a "C" average, but many students need higher GPAs in order to apply for professional school, graduate school, and entry-level jobs. Although extracurricular activities are often a positive and critical component of student life at U of W, administrators should consider providing a time management education and awareness course for all incoming students. After all, not every U of W graduate will be as lucky as Harry Wright. If UW students are going to succeed in business and higher education, they need to first understand the importance of time management.

Adapted from The Writing Center, University of Washington

1 Insert topic sentence: State the main idea of your paragraph and its relevance to your thesis/argument.

2 Introduce your evidence: Integrate your evidence by identifying the source and summarizing the context.

3 Insert evidence: Use appropriate evidence to support your claim. The evidence can be in the form of a quote, example, fact, statistic, etc.

4 Unpack evidence: Explain what the evidence means and how it connects to your argument.

5 Interpret evidence: Explain why and how the evidence is significant to your paragraph and/or your overall argument.

6 Insert conclusion: Provide a sentence that reasserts how your paragraph contributes to the development of your argument as a whole.

What is the purpose of a conclusion?

The conclusion summarizes your literature review including the key themes, overall findings, relevance of the topic to current knowledge, and future directions for research.

What should be included in a conclusion?

• Limitations

Summary of your Findings

• What are the key discoveries and outcomes of your literature review?
• What are some of the main points of similarity and difference?
• What are the main points of debate?
• What are the main patterns that have emerged?
• Has the approach to the topic changed over time?
• Revisit your Matrix to see your sources collectively.
• Review your topic sentences to see your main arguments.
• Highlight key findings of academic interest that may not already be known.
• Be concise and avoid restating what has already been summarized in the body of your literature review.

Concluding Statement about your Overall Findings

• What is your analysis of your findings?
• What do your findings combine to tell you and why is this significant?
• Ask yourself "so what?"
• Make sure your thesis and your overall conclusions align.

Relevance to current knowledge on the topic

• How do your findings contribute to the current discussion in the field?
• How are you building on the current discussion?
• How do your findings fit in with what has already been published?
• Revisit your Matrix to see the main findings and limitations of each study.
• Revisit the gaps you discovered in the body of knowledge on your topic and consider if your findings address them.

Directions for future research

• What research still needs to be done on or surrounding your topic?
• Can the gaps you discovered in the current body of literature be addressed through new approaches, questions, methodologies, or ideologies?
• What kind of research will benefit the body of knowledge on your topic the most? Why?
• Are any researchers or scholars trying new approaches, methodologies, or topics that can be used to address gaps in the body of knowledge in novel ways? If so, how?
• Revisit your Matrix to assess ways of filling gaps in the current body of knowledge.
• Make sure your recommendations are specific enough to be useful.
• Avoid generalizing and making assumptions.
• Explain the rationale behind your recommendations.
• Explain theoretical implications or practical applications of your findings.

Limitations of your research

• Have any constraints influenced your research or conclusions?
• Are your findings only valid in some contexts or to some researchers?
• Are there instances when your findings might not be applicable?
• Do the instances when your findings cannot be applied represent a gap in the current body of knowledge? If so, should research be conducted to address this gap?
• Be realistic and transparent regarding your findings and contributions to the current scholarly discussion on your topic.
• Considering how your findings can best be used may help you determine their limitations.

Different style guides use different reference list formats. For example, MLA requires a Works Cited page, whereas the Chicago Manual of Style requires a Bibliography. Be sure to carefully follow your citation style guide for reference list formatting.

Annotated Examples

Health sciences annotated literature review.

This annotated Literature Review is an example of a Standalone Literature Review

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Download the Health Sciences Annotated Literature Review .

Preview: Annotated Literature Review

History Annotated Literature Review

This annotated Literature Review is an example of an Embedded Literature Review

Download the History Annotated Literature Review .

Key Takeaways and References

• Write according to reader expectations.
• Be sure your evidence and analyses work together to support your main point.
• Use clear organization to ensure your points build on each other.

Swales, J., & Feak, C. (2013). Academic writing for graduate students. Ann Arbor, MI: University of Michigan Press

Reto Stöckli, NASA Earth Observatory. (2004). December, Blue Marble Next Generation W/ Topography and Bathymetry [Photograph], Retrieved October 12, 2016, from: http://visibleearth.nasa.gov/view.php?id=73909

University of Waterloo. (2016). Choose your scope [Illustration], Created October 17, 2016.

University of Waterloo. (2016). Choose your level of detail [Illustration], Created October 17, 2016.

University of Waterloo. (2016). Health Sciences Annotated Literature Review PDF.

University of Waterloo. (2016). History Annotated Literature Review PDF.

Next Section Overview

In Section D: Critical Writing Skills , you will learn the critical writing skills you need to use while writing your literature review.

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What is the Purpose of a Literature Review?

4-minute read

• 23rd October 2023

If you’re writing a research paper or dissertation , then you’ll most likely need to include a comprehensive literature review . In this post, we’ll review the purpose of literature reviews, why they are so significant, and the specific elements to include in one. Literature reviews can:

1. Provide a foundation for current research.

2. Define key concepts and theories.

3. Demonstrate critical evaluation.

4. Show how research and methodologies have evolved.

5. Identify gaps in existing research.

6. Support your argument.

Keep reading to enter the exciting world of literature reviews!

What is a Literature Review?

A literature review is a critical summary and evaluation of the existing research (e.g., academic journal articles and books) on a specific topic. It is typically included as a separate section or chapter of a research paper or dissertation, serving as a contextual framework for a study. Literature reviews can vary in length depending on the subject and nature of the study, with most being about equal length to other sections or chapters included in the paper. Essentially, the literature review highlights previous studies in the context of your research and summarizes your insights in a structured, organized format. Next, let’s look at the overall purpose of a literature review.

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Literature reviews are considered an integral part of research across most academic subjects and fields. The primary purpose of a literature review in your study is to:

Provide a Foundation for Current Research

Since the literature review provides a comprehensive evaluation of the existing research, it serves as a solid foundation for your current study. It’s a way to contextualize your work and show how your research fits into the broader landscape of your specific area of study.  

Define Key Concepts and Theories

The literature review highlights the central theories and concepts that have arisen from previous research on your chosen topic. It gives your readers a more thorough understanding of the background of your study and why your research is particularly significant .

Demonstrate Critical Evaluation 

A comprehensive literature review shows your ability to critically analyze and evaluate a broad range of source material. And since you’re considering and acknowledging the contribution of key scholars alongside your own, it establishes your own credibility and knowledge.

Show How Research and Methodologies Have Evolved

Another purpose of literature reviews is to provide a historical perspective and demonstrate how research and methodologies have changed over time, especially as data collection methods and technology have advanced. And studying past methodologies allows you, as the researcher, to understand what did and did not work and apply that knowledge to your own research.  

Identify Gaps in Existing Research

Besides discussing current research and methodologies, the literature review should also address areas that are lacking in the existing literature. This helps further demonstrate the relevance of your own research by explaining why your study is necessary to fill the gaps.

Support Your Argument

A good literature review should provide evidence that supports your research questions and hypothesis. For example, your study may show that your research supports existing theories or builds on them in some way. Referencing previous related studies shows your work is grounded in established research and will ultimately be a contribution to the field.  

Literature Review Editing Services 

Ensure your literature review is polished and ready for submission by having it professionally proofread and edited by our expert team. Our literature review editing services will help your research stand out and make an impact. Not convinced yet? Send in your free sample today and see for yourself! 

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The objective of a literature review

Questions to Consider

B. In some fields or contexts, a literature review is referred to as the introduction or the background; why is this true, and does it matter?

The elements of a literature review • The first step in scholarly research is determining the “state of the art” on a topic. This is accomplished by gathering academic research and making sense of it. • The academic literature can be found in scholarly books and journals; the goal is to discover recurring themes, find the latest data, and identify any missing pieces. • The resulting literature review organizes the research in such a way that tells a story about the topic or issue.

The literature review tells a story in which one well-paraphrased summary from a relevant source contributes to and connects with the next in a logical manner, developing and fulfilling the message of the author. It includes analysis of the arguments from the literature, as well as revealing consistent and inconsistent findings. How do varying author insights differ from or conform to previous arguments?

Language in Action

A. How are the terms “critique” and “review” used in everyday life? How are they used in an academic context?

In terms of content, a literature review is intended to:

• Set up a theoretical framework for further research • Show a clear understanding of the key concepts/studies/models related to the topic • Demonstrate knowledge about the history of the research area and any related controversies • Clarify significant definitions and terminology • Develop a space in the existing work for new research

The literature consists of the published works that document a scholarly conversation or progression on a problem or topic in a field of study. Among these are documents that explain the background and show the loose ends in the established research on which a proposed project is based. Although a literature review focuses on primary, peer -reviewed resources, it may begin with background subject information generally found in secondary and tertiary sources such as books and encyclopedias. Following that essential overview, the seminal literature of the field is explored. As a result, while a literature review may consist of research articles tightly focused on a topic with secondary and tertiary sources used more sparingly, all three types of information (primary, secondary, tertiary) are critical.

The literature review, often referred to as the Background or Introduction to a research paper that presents methods, materials, results and discussion, exists in every field and serves many functions in research writing.

Adapted from Frederiksen, L., & Phelps, S. F. (2017). Literature Reviews for Education and Nursing Graduate Students. Open Textbook Library

Review and Reinforce

Two common approaches are simply outlined here. Which seems more common? Which more productive? Why? A. Forward exploration 1. Sources on a topic or problem are gathered. 2. Salient themes are discovered. 3. Research gaps are considered for future research. B. Backward exploration 1. Sources pertaining to an existing research project are gathered. 2. The justification of the research project’s methods or materials are explained and supported based on previously documented research.

Media Attributions

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Sourcing, summarizing, and synthesizing:  Skills for effective research writing  Copyright © 2023 by Wendy L. McBride is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

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• Library Guides
• Literature Reviews
• Choosing a Type of Review

Literature Reviews: Choosing a Type of Review

Selecting a review type.

You'll want to think about the kind of review you are doing. Is it a selective or comprehensive review? Is the review part of a larger work or a stand-alone work ?

For example, if you're writing the Literature Review section of a journal article, that's a selective review which is part of a larger work. Alternatively, if you're writing a review article, that's a comprehensive review which is a stand-alone work. Thinking about this will help you develop the scope of the review.

Defining the Scope of Your Review

This exercise will help define the scope of your Literature Review, setting the boundaries for which literature to include and which to exclude.

A FEW GENERAL CONSIDERATIONS WHEN DEFINING SCOPE

• Which populations to investigate — this can include gender, age, socio-economic status, race, geographic location, etc., if the research area includes humans.
• What years to include — if researching the legalization of medicinal cannabis, you might only look at the previous 20 years; but if researching dolphin mating practices, you might extend many more decades.
• Which subject areas — if researching artificial intelligence, subject areas could be computer science, robotics, or health sciences
• How many sources  — a selective review for a class assignment might only need ten, while a comprehensive review for a dissertation might include hundreds. There is no one right answer.
• There will be many other considerations that are more specific to your topic. 

Most databases will allow you to limit years and subject areas, so look for those tools while searching. See the Searching Tips tab for information on how use these tools.

Four Common Types of Reviews

Literature review.

• Often used as a generic term to describe any type of review
• More precise definition:  Published materials that provide an examination of published literature . Can cover wide range of subjects at various levels of comprehensiveness.
• Identifies gaps in research, explains importance of topic, hypothesizes future work, etc.
• Usually written as part of a larger work like a journal article or dissertation

SCOPING REVIEW

• Conducted to address broad research questions with the goal of understanding the extent of research that has been conducted.
• Provides a preliminary assessment of the potential size and scope of available research literature. It aims to identify the nature and extent of research evidence (usually including ongoing research) 
• Doesn't assess the quality of the literature gathered (i.e. presence of literature on a topic shouldn’t be conflated w/ the quality of that literature)

SYSTEMATIC REVIEW

• Common in the health sciences
• Goal: collect all literature that meets specific criteria (methodology, population, treatment, etc.) and then appraise its quality and synthesize it
• Follows strict protocol for literature collection, appraisal and synthesis
• Typically performed by research teams 
• Takes 12-18 months to complete
• Often written as a stand alone work

META-ANALYSIS

• Goes one step further than a systematic review by statistically combining the results of quantitative studies to provide a more precise effect of the results. 
• Evidence Synthesis Guide Learn more about Systematic Reviews, Scoping Reviews, Rapid Reviews, Umbrella Reviews, Meta-Analyses

Attribution

Thanks to Librarian Jamie Niehof at the University of Michigan for providing permission to reuse and remix this Literature Reviews guide.

Evidence Synthesis Guide

• Evidence Synthesis Guide Learn more about Systematic Reviews, Scoping Reviews, Rapid Reviews, Umbrella Reviews, and Meta-Analyses

Which Review is Right for You?

The  Right Review tool  has questions about your lit review process and plans. It offers a qualitative and quantitative option. At completion, you are given a lit review type recommendation.

More Review Types

This article by Sutton & Booth (2019) explores 48 distinct types of Literature Reviews:

• Last Updated: Apr 4, 2024 4:51 PM
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• Volume 24, Issue 2
• Five tips for developing useful literature summary tables for writing review articles
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• http://orcid.org/0000-0003-0157-5319 Ahtisham Younas 1 , 2 ,
• http://orcid.org/0000-0002-7839-8130 Parveen Ali 3 , 4
• 1 Memorial University of Newfoundland , St John's , Newfoundland , Canada
• 2 Swat College of Nursing , Pakistan
• 3 School of Nursing and Midwifery , University of Sheffield , Sheffield , South Yorkshire , UK
• 4 Sheffield University Interpersonal Violence Research Group , Sheffield University , Sheffield , UK
• Correspondence to Ahtisham Younas, Memorial University of Newfoundland, St John's, NL A1C 5C4, Canada; ay6133{at}mun.ca

https://doi.org/10.1136/ebnurs-2021-103417

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Introduction

Literature reviews offer a critical synthesis of empirical and theoretical literature to assess the strength of evidence, develop guidelines for practice and policymaking, and identify areas for future research. 1 It is often essential and usually the first task in any research endeavour, particularly in masters or doctoral level education. For effective data extraction and rigorous synthesis in reviews, the use of literature summary tables is of utmost importance. A literature summary table provides a synopsis of an included article. It succinctly presents its purpose, methods, findings and other relevant information pertinent to the review. The aim of developing these literature summary tables is to provide the reader with the information at one glance. Since there are multiple types of reviews (eg, systematic, integrative, scoping, critical and mixed methods) with distinct purposes and techniques, 2 there could be various approaches for developing literature summary tables making it a complex task specialty for the novice researchers or reviewers. Here, we offer five tips for authors of the review articles, relevant to all types of reviews, for creating useful and relevant literature summary tables. We also provide examples from our published reviews to illustrate how useful literature summary tables can be developed and what sort of information should be provided.

Tip 1: provide detailed information about frameworks and methods

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Tabular literature summaries from a scoping review. Source: Rasheed et al . 3

The provision of information about conceptual and theoretical frameworks and methods is useful for several reasons. First, in quantitative (reviews synthesising the results of quantitative studies) and mixed reviews (reviews synthesising the results of both qualitative and quantitative studies to address a mixed review question), it allows the readers to assess the congruence of the core findings and methods with the adapted framework and tested assumptions. In qualitative reviews (reviews synthesising results of qualitative studies), this information is beneficial for readers to recognise the underlying philosophical and paradigmatic stance of the authors of the included articles. For example, imagine the authors of an article, included in a review, used phenomenological inquiry for their research. In that case, the review authors and the readers of the review need to know what kind of (transcendental or hermeneutic) philosophical stance guided the inquiry. Review authors should, therefore, include the philosophical stance in their literature summary for the particular article. Second, information about frameworks and methods enables review authors and readers to judge the quality of the research, which allows for discerning the strengths and limitations of the article. For example, if authors of an included article intended to develop a new scale and test its psychometric properties. To achieve this aim, they used a convenience sample of 150 participants and performed exploratory (EFA) and confirmatory factor analysis (CFA) on the same sample. Such an approach would indicate a flawed methodology because EFA and CFA should not be conducted on the same sample. The review authors must include this information in their summary table. Omitting this information from a summary could lead to the inclusion of a flawed article in the review, thereby jeopardising the review’s rigour.

Tip 2: include strengths and limitations for each article

Critical appraisal of individual articles included in a review is crucial for increasing the rigour of the review. Despite using various templates for critical appraisal, authors often do not provide detailed information about each reviewed article’s strengths and limitations. Merely noting the quality score based on standardised critical appraisal templates is not adequate because the readers should be able to identify the reasons for assigning a weak or moderate rating. Many recent critical appraisal checklists (eg, Mixed Methods Appraisal Tool) discourage review authors from assigning a quality score and recommend noting the main strengths and limitations of included studies. It is also vital that methodological and conceptual limitations and strengths of the articles included in the review are provided because not all review articles include empirical research papers. Rather some review synthesises the theoretical aspects of articles. Providing information about conceptual limitations is also important for readers to judge the quality of foundations of the research. For example, if you included a mixed-methods study in the review, reporting the methodological and conceptual limitations about ‘integration’ is critical for evaluating the study’s strength. Suppose the authors only collected qualitative and quantitative data and did not state the intent and timing of integration. In that case, the strength of the study is weak. Integration only occurred at the levels of data collection. However, integration may not have occurred at the analysis, interpretation and reporting levels.

Tip 3: write conceptual contribution of each reviewed article

While reading and evaluating review papers, we have observed that many review authors only provide core results of the article included in a review and do not explain the conceptual contribution offered by the included article. We refer to conceptual contribution as a description of how the article’s key results contribute towards the development of potential codes, themes or subthemes, or emerging patterns that are reported as the review findings. For example, the authors of a review article noted that one of the research articles included in their review demonstrated the usefulness of case studies and reflective logs as strategies for fostering compassion in nursing students. The conceptual contribution of this research article could be that experiential learning is one way to teach compassion to nursing students, as supported by case studies and reflective logs. This conceptual contribution of the article should be mentioned in the literature summary table. Delineating each reviewed article’s conceptual contribution is particularly beneficial in qualitative reviews, mixed-methods reviews, and critical reviews that often focus on developing models and describing or explaining various phenomena. Figure 2 offers an example of a literature summary table. 4

Tabular literature summaries from a critical review. Source: Younas and Maddigan. 4

Tip 4: compose potential themes from each article during summary writing

While developing literature summary tables, many authors use themes or subthemes reported in the given articles as the key results of their own review. Such an approach prevents the review authors from understanding the article’s conceptual contribution, developing rigorous synthesis and drawing reasonable interpretations of results from an individual article. Ultimately, it affects the generation of novel review findings. For example, one of the articles about women’s healthcare-seeking behaviours in developing countries reported a theme ‘social-cultural determinants of health as precursors of delays’. Instead of using this theme as one of the review findings, the reviewers should read and interpret beyond the given description in an article, compare and contrast themes, findings from one article with findings and themes from another article to find similarities and differences and to understand and explain bigger picture for their readers. Therefore, while developing literature summary tables, think twice before using the predeveloped themes. Including your themes in the summary tables (see figure 1 ) demonstrates to the readers that a robust method of data extraction and synthesis has been followed.

Tip 5: create your personalised template for literature summaries

Often templates are available for data extraction and development of literature summary tables. The available templates may be in the form of a table, chart or a structured framework that extracts some essential information about every article. The commonly used information may include authors, purpose, methods, key results and quality scores. While extracting all relevant information is important, such templates should be tailored to meet the needs of the individuals’ review. For example, for a review about the effectiveness of healthcare interventions, a literature summary table must include information about the intervention, its type, content timing, duration, setting, effectiveness, negative consequences, and receivers and implementers’ experiences of its usage. Similarly, literature summary tables for articles included in a meta-synthesis must include information about the participants’ characteristics, research context and conceptual contribution of each reviewed article so as to help the reader make an informed decision about the usefulness or lack of usefulness of the individual article in the review and the whole review.

In conclusion, narrative or systematic reviews are almost always conducted as a part of any educational project (thesis or dissertation) or academic or clinical research. Literature reviews are the foundation of research on a given topic. Robust and high-quality reviews play an instrumental role in guiding research, practice and policymaking. However, the quality of reviews is also contingent on rigorous data extraction and synthesis, which require developing literature summaries. We have outlined five tips that could enhance the quality of the data extraction and synthesis process by developing useful literature summaries.

• Aromataris E ,
• Rasheed SP ,

Twitter @Ahtisham04, @parveenazamali

Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

Competing interests None declared.

Patient consent for publication Not required.

Provenance and peer review Not commissioned; externally peer reviewed.

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Once Upon a Time, the World of Picture Books Came to Life

The tale behind a new museum of children’s literature is equal parts imagination, chutzpah and “The Little Engine That Could.”

By Elisabeth Egan

Photographs and Video by Chase Castor

Elisabeth Egan followed the Rabbit Hole as it was nearing completion. She has written about several of its inhabitants for The Times.

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Before we get into what the Rabbit Hole is, here’s what it isn’t: a place with touch screens, a ball pit, inscrutable plaques, velvet ropes, a cloying soundtrack or adults in costumes. It doesn’t smell like graham crackers, apple juice or worse (yet). At $16 per person over 2 years old, it also isn’t cheap.

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Cowdin, Pettid and their team are those students, all grown up.

The main floor of the Rabbit Hole consists of 40 book-themed dioramas blown up to life-size and arranged, Ikea showroom-style, in a space the size of two hockey rinks. The one inspired by John Steptoe’s “ Uptown ” features a pressed tin ceiling, a faux stained-glass window and a jukebox. In the great green room from “ Goodnight Moon ,” you can pick up an old-fashioned phone and hear the illustrator’s son reading the story.

One fictional world blends into the next, allowing characters to rub shoulders in real life just as they do on a shelf. Visitors slid down the pole in “The Fire Cat,” slithered into the gullet of the boa constrictor in “ Where the Sidewalk Ends ” and lounged in a faux bubble bath in “ Harry the Dirty Dog .” There are plenty of familiar faces — Madeline , Strega Nona , Babar — but just as many areas dedicated to worthy titles that don’t feature household names, including “ Crow Boy ,” “ Sam and the Tigers ,” “ Gladiola Garden ” and “ The Zabajaba Jungle .”

Emma Miller, a first-grade teacher, said, “So many of these are books I use in my classroom. It’s immersive and beautiful. I’m overwhelmed.”

As her toddler bolted toward “ Frog and Toad ,” Taylar Brown said, “We love opportunities to explore different sensory things for Mason. He has autism so this is a perfect place for him to find little hiding holes.”

A gaggle of boys reclined on a bean bag in “ Caps for Sale ,” passing around a copy of the book. Identical twins sounded out “ Bread and Jam for Frances ” on the pink rug in the badger’s house. A 3-year-old visiting for the second time listened to her grandfather reading “The Tawny Scrawny Lion.”

Tomy Tran, a father of three from Oklahoma, said, “I’ve been to some of these indoor places and it’s more like a jungle gym. Here, my kids will go into the area, pick up the book and actually start reading it as if they’re in the story.”

All the titles scattered around the museum are available for purchase at the Lucky Rabbit, a bookstore arranged around a cozy amphitheater. Pettid and Cowdin estimate that they’ve sold one book per visitor, with around 650 guests per day following the pink bunny tracks from the parking lot.

Once upon a time, Cowdin and Pettid owned the Reading Reptile, a Kansas City institution known not just for its children’s books but also for its literary installations. When Dav Pilkey came to town, Pettid and Cowdin welcomed him by making a three-and-a-half foot papier-mâché Captain Underpants. Young customers pitched in to build Tooth-Gnasher Superflash or the bread airplane from “In the Night Kitchen.”

One of the store’s devotees was Meg McMath, who continued to visit through college, long after she’d outgrown its offerings (and its chairs). Now 36, McMath traveled from Austin, Texas with her husband and six-month-old son to see the Rabbit Hole. “I’ve cried a few times,” she said.

The Reading Reptile weathered Barnes & Noble superstores and Amazon. Then came “the Harry Potter effect,” Pettid said, “where all of a sudden adults wanted kids to go from picture books to thick chapter books. They skipped from here to there; there was so much they were missing.”

As parents fell under the sway of reading lists for “gifted” kids, story time became yet another proving ground.

“It totally deformed the reading experience,” Cowdin said. Not to mention the scourge of every bookstore: surreptitious photo-snappers who later shopped online.

In 2016, Cowdin and Pettid closed the Reptile to focus on the Rabbit Hole, an idea they’d been percolating for years. They hoped it would be a way to spread the organic bookworm spirit they’d instilled in their five children while dialing up representation for readers who had trouble finding characters who looked like them. The museum would celebrate classics, forgotten gems and quality newcomers. How hard could it be?

Cowdin and Pettid had no experience in the nonprofit world. They knew nothing about fund-raising or construction. They’re ideas people, glass half full types, idealists but also stubborn visionaries. They didn’t want to hand their “dream” — a word they say in quotes — to consultants who knew little about children’s books. Along the way, board members resigned. Their kids grew up. Covid descended. A tree fell on their house and they had to live elsewhere for a year. “I literally have told Pete I quit 20 times,” Pettid said.

“It has not always been pleasant,” Cowdin said. “But it was just like, OK, we’re going to do this and then we’re going to figure out how to do it. And then we just kept figuring it out.”

Little by little, chugging along like “ The Little Engine That Could ,” they raised $15 million and assembled a board who embraced their vision and commitment to Kansas City. They made a wish list of books — “Every ethnicity. Every gender. Every publisher,” Pettid said — and met with rights departments and authors’ estates about acquiring permissions. Most were receptive; some weren’t. (They now have rights to more than 70 titles.)

“A lot of people think a children’s bookstore is very cute,” Pettid said. “They have a small mind for children’s culture. That’s why we had to buy this building.”

For $2 million, they bought the factory from Robert Riccardi, an architect whose family operated a beverage distribution business there for two decades. His firm, Multistudio, worked with Cowdin and Pettid to reimagine the space, which sits on an industrial corner bordered by train tracks, highways and skyline views.

Cowdin and Pettid started experimenting with layouts. Eventually they hired 39 staff members, including 21 full-time artists and fabricators who made everything in the museum from some combination of steel, wood, foam, concrete and papier-mâché.

“My parents are movers and shakers,” Gloria Cowdin said. She’s the middle of the five siblings, named after Frances the badger’s sister — and, yes, that’s her voice reading inside the exhibit. “There’s never been something they’ve wanted to achieve that they haven’t made happen, no matter how crazy.”

During a sneak peek in December, it was hard to imagine how this semi-construction zone would coalesce into a museum. The 22,000 square foot fabrication section was abuzz with drills and saws. A whiteboard showed assembly diagrams and punch lists. (Under “Random jobs,” someone had jotted, “Write Christmas songs.”) The entryway and lower level — known as the grotto and the burrow — were warrens of scaffolding and machinery.

But there were pockets of calm. Kelli Harrod worked on a fresco of trees outside the “ Blueberries for Sal ” kitchen, unfazed by the hubbub. In two years as lead painter, she’d witnessed the Rabbit Hole’s steady growth.

“I remember painting the ‘ Pérez and Martina ’ house before there was insulation,” Harrod said. “I was bundled up in hats, gloves and coats, making sure my hands didn’t shake.”

Leigh Rosser was similarly nonplused while describing his biggest challenge as design fabrication lead. Problem: How to get a dragon and a cloud to fly above a grand staircase in “ My Father’s Dragon .” Solution: “It’s really simple, conceptually” — it didn’t sound simple — “but we’re dealing with weight in the thousands of pounds, mounted up high. We make up things that haven’t been done before, or at least that I’m not aware of.”

Attention to detail extends to floor-bound exhibits. The utensil drawer in “Blueberries for Sal” holds Pete Cowdin’s mother’s egg whisk alongside a jar containing a baby tooth that belonged to Cowdin and Pettid’s oldest daughter, Sally. The tooth is a wink at “ One Morning in Maine ,” an earlier Robert McCloskey book involving a wiggly bicuspid — or was it a molar? If dental records are available, Cowdin and Pettid have consulted them for accuracy.

“With Pete and Deb, it’s about trying to picture what they’re seeing in their minds,” said Brian Selznick , a longtime friend who helped stock the shelves in the Lucky Rabbit. He’s the author of “ The Invention of Hugo Cabret ,” among many other books.

Three months ago, the grotto looked like a desert rock formation studded with pink Chiclets. The burrow, home of Fox Rabbit, the museum’s eponymous mascot, was dark except for sparks blasting from a soldering iron. The floor was covered with tiny metal letters reclaimed from a newly-renovated donor wall at a local museum.

Cowdin and Pettid proudly explained their works-in-progress; these were the parts of the museum that blossomed from seed in their imaginations. But to the naked eye, they had the charm of a bulkhead door leading to a scary basement.

When the museum opened to the public, the grotto and the burrow suddenly made sense. The pink Chiclets are books, more than 3000 of them — molded in silicone, cast in resin — incorporated into the walls, the stairs and the floor. They vary from an inch-and-a-half to three inches thick. As visitors descend into the Rabbit Hole, they can run their fingers over the edges of petrified volumes. They can clamber over rock formations that include layers of books. Or they can curl up and read.

Dennis Butt, another longtime Rabbit Hole employee, molded 92 donated books into the mix, including his own copies of “ The Hobbit ” and “ The Lord of the Rings .” He said, “They’re a little piece of me.”

As for the metal letters, they’re pressed into the walls of a blue-lit tunnel leading up a ramp to the first floor. They spell the first lines of 141 books, including “ Charlotte’s Web ,” “Devil in the Drain” and “ Martha Speaks .” Some were easier to decipher than others, but “Mashed potatoes are to give everybody enough” jumped out. It called to mind another line from “A Hole is to Dig,” Ruth Krauss’s book of first definitions (illustrated by a young Maurice Sendak ): “The world is so you have something to stand on.”

At the Rabbit Hole, books are so you have something to stand on. They’re the bedrock and the foundation; they’re the solid ground.

Cowdin and Pettid have plans to expand into three more floors, adding exhibit space, a print shop, a story lab, a resource library and discovery galleries. An Automat-style cafeteria and George and Martha -themed party and craft room will open soon. A rooftop bar is also in the works.

Of course, museum life isn’t all happily ever after. Certain visitors whined, whinged and wept, especially as they approached the exit. One weary adult said, “Charlie, we did it all.”

Then, “Charlie, it’s time to go.”

And finally, “Fine, Charlie, we’re leaving you here.” Cue hysteria.

But the moral of this story — and the point of the museum, and maybe the point of reading, depending on who you share books with — crystallized in a quiet moment in the great green room. A boy in a Chiefs Super Bowl T-shirt pretended to fall asleep beneath a fleecy blanket. Before closing his eyes, he said, “Goodnight, Grandma. Love you to the moon.”

Elisabeth Egan is a writer and editor at the Times Book Review. She has worked in the world of publishing for 30 years. More about Elisabeth Egan

The Great Read

Here are more fascinating tales you can’t help reading all the way to the end..

Deathbed Visions: Researchers are documenting deathbed visions , a phenomenon that seems to help the dying, as well as those they leave behind.

The Pants Pendulum: Around 2020, the “right” pants began to swing from skinny to wide. But is there even a consensus around trends anymore ?

The Psychic Peril of Mars: NASA is conducting tests on what might be the greatest challenge of a human mission to the red planet: the trauma of isolation .

Saved by a Rescue Dog: He spent 13 years addicted to cocaine. Running a shelter for abused and neglected dogs in New York has kept him sober, but it hasn’t been easy .

An Art Mogul's Fall: After a dramatic rise in business and society, Louise Blouin finds herself unloading a Hamptons dream home in bankruptcy court .

• Open access
• Published: 05 September 2022

Psychiatric and medical comorbidities of eating disorders: findings from a rapid review of the literature

• Ashlea Hambleton 1 ,
• Genevieve Pepin 2 ,
• Anvi Le 3 ,
• Danielle Maloney 1 , 4 ,
• National Eating Disorder Research Consortium ,
• Stephen Touyz 1 , 4 &
• Sarah Maguire 1 , 4  

Journal of Eating Disorders volume  10 , Article number:  132 ( 2022 ) Cite this article

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Eating disorders (EDs) are potentially severe, complex, and life-threatening illnesses. The mortality rate of EDs is significantly elevated compared to other psychiatric conditions, primarily due to medical complications and suicide. The current rapid review aimed to summarise the literature and identify gaps in knowledge relating to any psychiatric and medical comorbidities of eating disorders.

This paper forms part of a rapid review) series scoping the evidence base for the field of EDs, conducted to inform the Australian National Eating Disorders Research and Translation Strategy 2021–2031, funded and released by the Australian Government. ScienceDirect, PubMed and Ovid/Medline were searched for English-language studies focused on the psychiatric and medical comorbidities of EDs, published between 2009 and 2021. High-level evidence such as meta-analyses, large population studies and Randomised Control Trials were prioritised.

A total of 202 studies were included in this review, with 58% pertaining to psychiatric comorbidities and 42% to medical comorbidities. For EDs in general, the most prevalent psychiatric comorbidities were anxiety (up to 62%), mood (up to 54%) and substance use and post-traumatic stress disorders (similar comorbidity rates up to 27%). The review also noted associations between specific EDs and non-suicidal self-injury, personality disorders, and neurodevelopmental disorders. EDs were complicated by medical comorbidities across the neuroendocrine, skeletal, nutritional, gastrointestinal, dental, and reproductive systems. Medical comorbidities can precede, occur alongside or emerge as a complication of the ED.

Conclusions

This review provides a thorough overview of the comorbid psychiatric and medical conditions co-occurring with EDs. High psychiatric and medical comorbidity rates were observed in people with EDs, with comorbidities contributing to increased ED symptom severity, maintenance of some ED behaviours, and poorer functioning as well as treatment outcomes. Early identification and management of psychiatric and medical comorbidities in people with an ED may improve response to treatment and overall outcomes.

Plain English Summary

The mortality rate of eating disorders is significantly elevated compared to other psychiatric conditions, primarily due to medical complications and suicide. Further, individuals with eating disorders often meet the diagnostic criteria of at least one comorbid psychiatric or medical disorder, that is, the individual simultaneously experiences both an ED and at least one other condition. This has significant consequences for researchers and health care providers – medical and psychiatric comorbidities impact ED symptoms and treatment effectiveness. The current review is part of a larger Rapid Review series conducted to inform the development of Australia’s National Eating Disorders Research and Translation Strategy 2021–2031. A Rapid Review is designed to comprehensively summarise a body of literature in a short timeframe, often to guide policymaking and address urgent health concerns. The Rapid Review synthesises the current evidence base and identifies gaps in eating disorder research and care. This paper gives a critical overview of the scientific literature relating to the psychiatric and medical comorbidities of eating disorders. It covers recent literature regarding psychiatric comorbidities including anxiety disorders, mood disorders, substance use disorders, trauma and personality disorders and neurodevelopmental disorders. Further, the review discusses the impact and associations between EDs and medical comorbidities, some of which precede the eating disorder, occur alongside, or as a consequence of the eating disorder.

Introduction

Eating Disorders (EDs) are often severe, complex, life-threatening illnesses with significant physiological and psychiatric impacts. EDs impact individuals across the entire lifespan, affecting all age groups (although most often they emerge in childhood and adolescence), genders, socioeconomic groups and cultures [ 1 ]. EDs have some of the highest mortality rates of all psychiatric illnesses and carry a significant personal, interpersonal, social and economic burdens [ 2 , 3 ].

Adding to the innate complexity of EDs, it is not uncommon for people living with an ED to experience associated problems such as psychological, social, and functional limitations [ 2 ] in addition to psychiatric and medical comorbidities [ 4 , 5 , 6 ]. Comorbidity is defined as conditions or illnesses that occur concurrently to the ED. Evidence suggests that between 55 and 95% of people diagnosed with an ED will also experience a comorbid psychiatric disorder in their lifetime [ 4 , 6 ]. Identifying psychiatric comorbidities is essential because of their potential impact on the severity of ED symptomatology, the individual’s distress and treatment effectiveness [ 7 , 8 ].

The mortality rate of EDs is significantly higher than the general population, with the highest occurring in Anorexia Nervosa (AN) due to impacts on the cardiovascular system [ 9 ] and suicide. [ 10 ] Mortality rates are also heightened in Bulimia Nervosa (BN) and Other Specified Feeding and Eating Disorder (OSFED) [ 11 ]. Suicide rates are elevated across the ED spectrum, and higher rates are observed in patients with a comorbid psychiatric disorder [ 10 , 12 ]. Of concern, the proportion of people with an ED not accessing treatment is estimated to be as high as 75% [ 13 ], potentially a consequence of comorbidities which impact on motivation, the ability to schedule appointments or require clinical prioritisation (i.e., self-harm or suicidal behaviours) [ 14 ]. Further, for many of those diagnosed with an ED who access treatment, recovery is a lengthy process. A longitudinal study found approximately two-thirds of participants with AN or BN had recovered by 22 years follow-up [ 15 ]. Although recovery occurred earlier for those with BN, illness duration was lengthy for both groups with quality of life and physical health impacts [ 15 ]. Further, less is known regarding the illness trajectory for those who do not receive treatment.

Medical comorbidities associated with EDs can range from mild to severe and life-threatening, with complications observed across all body systems, including the cardiac, metabolic and gastrointestinal, and reproductive systems [ 5 ]. These comorbidities and complications can place people at increased risk of medical instability and death [ 5 ]. Therefore, understanding how co-occurring medical comorbidities and complications impact EDs is critical to treatment and recovery.

In addition to ED-associated medical comorbidities, EDs often present alongside other psychiatric conditions. Psychiatric comorbidities in people with EDs are associated with higher health system costs, emergency department presentations and admissions [ 16 ]. Comorbidities may precede the onset of the ED, be co-occurring, or result from symptoms and behaviours associated with the ED [ 17 , 18 ]. Individuals with an ED, their carers and care providers often face a complex and important dilemma; the individual with an ED requires treatment for their ED but also for their psychiatric comorbidities, and it can be difficult for treatment providers to determine which is the clinical priority [ 19 ]. This is further complicated by the fact that EDs and comorbidities may have a reciprocal relationship, whereby the presence of one impact the pathology, treatment and outcomes of the other.

The current Rapid Review (RR) forms part of a series of reviews commissioned by the Australian Federal Government to inform the Australian National Eating Disorders Research and Translation Strategy 2021–2031 [ 20 ]. In response to the impact of psychiatric and medical comorbidities on outcomes, this rapid review summarises the recent literature on the nature and implications of psychiatric and medical comorbidities associated with EDs.

The Australian Government Commonwealth Department of Health funded the InsideOut Institute for Eating Disorders (IOI) to develop the Australian Eating Disorders Research and Translation Strategy 2021–2031 [ 20 ] under the Psych Services for Hard to Reach Groups initiative (ID 4-8MSSLE). The strategy was developed in partnership with state and national stakeholders including clinicians, service providers, researchers, and experts by lived experience (both consumers and families/carers). Developed through a two-year national consultation and collaboration process, the strategy provides the roadmap to establishing EDs as a national research priority and is the first disorder-specific strategy to be developed in consultation with the National Mental Health Commission. To inform the strategy, IOI commissioned Healthcare Management Advisors (HMA) to conduct a series of RRs to assess all available peer-reviewed literature on all DSM-5 listed EDs.

A RR Protocol [ 21 ] was utilised to allow swift synthesis of the evidence in order to guide public policy and decision-making [ 22 ]. This approach has been adopted by several leading health organisations including the World Health Organisation [ 17 ] and the Canadian Agency for Drugs and Technologies in Health Rapid Response Service [ 18 ], to build a strong evidence base in a timely and accelerated manner, without compromising quality. A RR is not designed to be as comprehensive as a systematic review—it is purposive rather than exhaustive and provides actionable evidence to guide health policy [ 23 ].

The RR is a narrative synthesis adhering to the PRISMA guidelines [ 24 ]. It is divided by topic area and presented as a series of papers. Three research databases were searched: ScienceDirect, PubMed and Ovid/Medline. To establish a broad understanding of the progress made in the field of EDs, and to capture the largest evidence base from the past 12 years (originally 2009–2019, but expanded to include the preceding two years), the eligibility criteria for included studies were kept broad. Therefore, included studies were published between 2009 and 2021, written in English, and conducted within Western healthcare systems or health systems comparable to Australia in terms of structure and resourcing. The initial search and review process was conducted by three reviewers between 5 December 2019 and 16 January 2020. The re-run for the years 2020–2021 was conducted by two reviewers at the end of May 2021.

The RR had a translational research focus with the objective of identifying evidence relevant to developing optimal care pathways. Searches therefore used a Population, Intervention, Comparison, Outcome (PICO) approach to identify literature relating to population impact, prevention and early intervention, treatment, and long-term outcomes. Purposive sampling focused on high-level evidence studies encompassing meta-analyses; systematic reviews; moderately sized randomised controlled studies (RCTs) (n > 50); moderately sized controlled-cohort studies (n > 50); and population studies (n > 500). However, the diagnoses ARFID and UFED necessitated less stringent eligibility criteria due to a paucity of published articles. As these diagnoses are newly captured in the DSM-5 (released in 2013, within the allocated search timeframe), the evidence base is still emerging, and few studies have been conducted. Thus, smaller studies (n =  ≤ 20) and narrative reviews were also considered and included. Grey literature, such as clinical or practice guidelines, protocol papers (without results) and Masters’ theses or dissertations, were excluded. Other sources (which may not be replicable when applying the current methodology) included the personal libraries of authors, yielding two additional studies (see Additional file 1 ). This extra step was conducted in line with the PRISMA-S: an extension to the PRISMA Statement for Reporting Literature Searches in Systematic Reviews [ 25 ].

Full methodological details including eligibility criteria, search strategy and terms and data analysis are published in a separate protocol paper, which included a total of 1320 studies [ 26 ] (see Additional file 1 : Fig. S1 for PRISMA flow diagram). Data from included studies relating to psychiatric and medical comorbidities of EDs were synthesised and are presented in the current review. No further analyses were conducted.

The search included articles published in the period January 2009 to May 2021. The RR identified 202 studies for inclusion. Of these, 58% related to psychiatric comorbidities (n = 117) and 42% to medical comorbidities (n = 85). A full list of the studies included in this review and information about population, aims and results can be found in Additional file 2 : Tables S3, S4. Results are subdivided into two categories: (1) psychiatric comorbidities and (2) medical complications. Tables 1 and 2 provide high-level summaries of the results.

Psychiatric comorbidities

The study of psychiatric comorbidities can assist with developing models of ED aetiology, conceptualising psychopathology and has relevance for treatment development and outcomes. Given that common psychological factors are observed across psychiatric disorders [ 87 ], it is not surprising that there are high prevalence rates of co-occurring psychiatric conditions with EDs. Comorbidity rates of EDs and other psychiatric conditions are elevated further in ethnic/racial minority groups [ 88 ]. When looking at the evidence from studies conducted with children and young people, one study of children with ARFID found that 53% of the population had a lifetime comorbid psychiatric disorder [ 89 ]. It emerged from the RR that research regarding psychiatric comorbidities generally focussed on the prevalence rates of comorbidities among certain ED subgroups, with some also exploring implications for treatment and ED psychopathology.

Anxiety disorders

Research indicates that EDs and anxiety disorders frequently co-occur [ 8 , 27 ]. The high prevalence rates of anxiety disorders in the general population are also observed in people with EDs; with a large population study finding anxiety disorders were the most frequently comorbid conditions reported [ 8 ]. In a study of women presenting for ED treatment, 65% also met the criteria for at least one comorbid anxiety disorder [ 28 ]. Of note, 69% of those endorsing the comorbidity also reported that the anxiety disorder preceded the onset of the ED [ 28 ]. Another study explored anxiety across individuals with an ED categorised by three weight ranges (individuals whose weight is in the ‘healthy weight’ range, individuals in the ‘overweight’ range and individuals in the ‘obese’ range). While anxiety was elevated across all groups, the authors did note that individuals in the overweight group reported significantly higher rates of anxiety than individuals within the healthy weight group [ 90 ]. One study that explored temperamental factors provided some insight into factors that may mediate this association; anxiety sensitivity (a predictor of anxiety disorders) was associated with greater ED severity among individuals in a residential ED treatment facility [ 29 ]. Further, this association was mediated by a tendency to engage in experiential avoidance—the authors noting that individuals with greater ED symptoms were more likely to avoid distressing experiences [ 29 ].

Generalised anxiety disorder (GAD)

Studies have noted the potential genetic links between EDs and GAD, noting that the presence of one significantly increases the likelihood of the other [ 8 , 30 ]. Further, there appears to be a relationship between the severity of ED behaviours and the co-occurrence of GAD, with comorbidity more likely when fasting and excessive exercise are present, as well as a lower BMI [ 30 ]. The authors noted the particularly pernicious comorbidity of EDs (specifically AN) and GAD may be amplified by the jointly anxiolytic and weight loss effects of food restriction and excessive exercise [ 30 ].

Social anxiety

A meta-analysis of 12 studies found higher rates of social anxiety across all ED diagnoses, with patients with BN demonstrating the highest rate of comorbidity at 84.5%, followed by both BED and AN-BP both at 75% [ 31 ]. High levels of social anxiety were also associated with more severe ED psychopathology [ 31 ] and higher body weight [ 91 ]. This particular comorbidity may also impact on access to treatment for the ED; a large follow-up study of adolescents found that self-reported social phobia predicted not seeking treatment for BN symptoms [ 32 ]. Interestingly, two studies noted that anxiety symptoms improved following psychological treatments that targeted ED symptoms, possibly due to a shared symptom profile [ 29 , 31 ].

Obsessive–compulsive disorder

Similarities between the symptoms of Obsessive–Compulsive Disorder (OCD) and EDs, such as cognitive rigidity, obsessiveness, detail focus, perfectionism and compulsive routines have long been reported in the literature [ 34 ]. Given the symptom overlap, a meta-analysis sought to clarify the lifetime and current (that is, a current diagnosis at the time of data collection) comorbidity rates of OCD and EDs, noting the lifetime comorbidity rate was 18% and current comorbidity rate was 15% [ 33 ]. However, the authors noted that this prevalence may double over longer periods of observation, with some follow-up data demonstrating comorbidity rates of 33% [ 33 ]. Prevalence rates of OCD seemed to be highest among people with AN (lifetime = 19% and current = 14%) compared to other ED subtypes. In addition to the symptom crossover, this RR found evidence of a complex relationship between OCD and EDs, including a potential association between OCD and greater ED severity [ 34 ].

Network analysis found that doubts about simple everyday things and repeating things over and over bridged between ED and OCD symptoms. Further, a pathway was observed between restricting and checking compulsions and food rigidity as well as binge eating and hoarding. However, as the data was cross-sectional, directional inferences could not be made [ 36 ]. An earlier study explored how changes in OCD symptoms impact ED symptoms among an inpatient sample [ 35 ]. As was hypothesised, decreases in OCD symptoms accounted for significant variance in decreases in ED symptoms, and this effect was strongest among ED patients with comorbid OCD. The study also found that irrespective of whether patients had comorbid OCD or not, when ED symptoms improved, so did symptoms of OCD [ 35 ]. The authors concluded that perhaps there is a reciprocal relationship between OCD and ED symptoms, whereby symptoms of both conditions interact in a synergistic, bidirectional manner, meaning that improvement in one domain can lead to improvement in another [ 35 ]. These findings were somewhat supported in a study by Simpson and colleagues (2013), which found exposure and response prevention (a specialised OCD treatment) resulted in a significant reduction in OCD severity, as was expected, and an improvement in ED symptoms. In their study, individuals with BN showed more improvement than those with AN–nevertheless, BMI still increased among those underweight [ 92 ].

Mood disorders

Depression and major depressive disorder (mdd).

This RR also found high levels of comorbidity between major depression and EDs. A longitudinal study of disordered eating behaviours among adolescents found that disordered eating behaviours and depressive symptoms developed concurrently [ 37 ]. Among the sample, over half the adolescent sample had a depressive disorder. Prevalence rates were similar for AN (51.5%) and BN (54%) [ 37 ]. The study also explored the neurological predictors of comorbid depression in individuals with EDs, noting that lower grey matter volumes in the medial orbitofrontal, dorsomedial, and dorsolateral prefrontal cortices predicted the concurrent development of purging and depressive symptoms [ 37 ]. The results suggested that alterations in frontal brain circuits were part of a neural aetiology common to EDs and depression [ 37 ].

This RR found much support for a strong relationship between depression and ED symptomatology. In a study of patients with AN, comorbid MDD was associated with a greater AN symptom severity [ 93 ], and this relationship between the symptoms of MDD and AN was bidirectional in a study of adolescents undergoing treatment for AN, whereby dietary restraint predicted increased guilt and hostility (symptoms of low mood) and fear predicted further food restriction [ 94 ]. Further studies noted the association between BN, BED and NES, with a higher prevalence of depression and more significant depression symptoms [ 95 , 96 , 97 ]. However, other studies have failed to find support for this association–for example, a Swedish twin study found no association between NES and other mental health disorders [ 98 ].

The impact of the relationship between depression and EDs on treatment outcomes was variable across the studies identified by the RR. One study noted the impact of depression on attrition; patients with BN and comorbid depression attending a university clinic had the highest rates of treatment drop-out [ 99 ]. However, in a sample of patients with AN, the comorbidity of depression (or lack of) did not impact treatment outcome and the severity of depression was not associated with changes in ED symptoms [ 100 ]. This finding was supported in another study of inpatients with AN; pre-treatment depression level did not predict treatment outcome or BMI [ 101 ].

Bipolar disorders

Notable comorbidity rates between bipolar disorders (BD) and EDs were reported in the literature reviewed, however evidence about the frequency of this association was mixed. Studies noted comorbidity rates of BD and EDs ranging between 1.9% to as high as 35.8% [ 38 , 39 , 40 ]. In order to better understand the nature of comorbidity, a recent systematic review and meta-analysis found BD (including bipolar 1 disorder and bipolar 2 disorder) and ED comorbidity varied across different ED diagnostic groups (BED—12.5%, BN—7.4%, AN—3.8%) [ 102 ]. However, the authors noted the scant longitudinal studies available, particularly in paediatric samples. An analysis of comorbidity within a sample of patients with BD identified that 27% of participants also met criteria for an ED; 15% had BN, 12% had BED, and 0.2% had AN [ 103 ]. Two other studies noted considerable comorbidity rates of BD; 18.6% for binge eating [ 104 ] and 8.8% for NES [ 105 ]. Some studies suggested the co-occurrence of BD and EDs were seen most in people with AN-BP, BN and BED—all of which share a binge and/or purge symptom profile [ 38 , 106 ]. Specifically, BED and BN were the most common co-occurring EDs with BD [ 40 ], however, these EDs are also the most prevalent in the population. Therefore, it is unclear if this finding is reflective of the increased prevalence of BN and BED, or if it reflects a shared underlying psychopathology between BD and these EDs [ 40 ].

Comorbid ED-BD patients appear to experience increased ED symptom severity, poorer daily and neuropsychological functioning than patients with only a ED or BD diagnosis [ 107 ]. In an effort to understand which shared features in ED-BD relate to quality of life, one study assessed an adult sample with BD [ 108 ]. Binge eating, restriction, overevaluation of weight and shape, purging and driven exercise were associated with poorer clinical outcomes, quality of life and mood regulation [ 108 ]. Additionally, a study of patients undergoing treatment for BD noted patients with a comorbid ED had significantly poorer clinical outcomes and higher scores of depression [ 109 ]. Further, quality of life was significantly lower among patients with comorbid ED-BD [ 109 ]. The comorbidity of ED and BD has implications for intervention and clinical management, as at least one study observed higher rates of alcohol abuse and suicidality among patients with comorbid ED and BD compared to those with BD only [ 40 ].

Personality disorders

This RR identified limited research regarding the comorbidity between personality disorders (PD) and EDs. A meta-analysis sought to summarise the proportion of comorbid PDs among patients with AN and BN [ 41 ]. There was a heightened association between any type of ED and PDs, and this was significantly different to the general population. For specific PDs, the proportions of paranoid, borderline, avoidant, dependant and obsessive–compulsive PD were significantly higher in EDs than in the general population. For both AN and BN, Cluster C PDs (avoidant, dependant and obsessive–compulsive) were most frequent. The authors noted that the specific comorbidity between specific EDs and PDs appears to be associated with common traits—constriction/perfectionism and rigidity is present in both AN and obsessive–compulsive PD (which had a heightened association), as was the case with impulsivity, a characteristic of both BN and borderline PD [ 41 ]. This symptom association was also observed in a study of adolescents admitted to an ED inpatient unit whereby a significant interaction between binge-purge EDs (AN-BP and BN), childhood emotional abuse (a risk factor for PD) and borderline personality style was found [ 110 ].

This comorbidity may be associated with greater patient distress and have implications for patient outcomes [ 41 , 42 ]. Data from a nine-year observational study of individuals with BN reported that comorbidity with a PD was strongly associated with elevated mortality risk [ 111 ]. In terms of treatment outcomes, an RCT compared the one- and three-year treatment outcomes of four subgroups of women with BN, defined by PD complexity; no comorbid PD (health control), personality difficulties, simple PD and complex PD [ 112 ]. At pre-treatment, the complex PD group had greater ED psychopathology than the other three groups. Despite this initial difference, there were no differences in outcomes between groups at one-year and three-year follow up [ 112 ]. The authors suggested this result could be due to the targeting of the shared symptoms of BN and PD by the intervention delivered in this study, and that as ED symptoms improve, so do PD symptoms [ 112 ]. Suggesting that beyond symptom overlap, perhaps some symptoms attributed to the PD are better explained by the ED. This was consistent with Brietzke and colleagues’ (2011) recommendation that for individuals with ED and a comorbid PD, treatment approaches should target both conditions where possible [ 113 ].

Substance use disorders

Comorbid substance use disorders (SUDs) are also often noted in the literature as an issue that complicates treatment and outcomes of EDs [ 114 ]. A meta-analysis reported the lifetime prevalence of EDs and comorbid SUD was 27.9%, [ 43 ] with a lifetime prevalence of comorbid illicit drug use of 17.2% for AN and 18.6% for BN [ 115 ]. Alcohol, caffeine and tobacco were the most frequently reported comorbidities [ 43 ]. Further analysis of SUDs by substance type in a population-based twin sample indicated that the lifetime prevalence of an alcohol use disorder among individuals with AN was 22.4% [ 115 ]. For BN, the prevalence rate was slightly higher at 24.0% [ 115 ].

The comorbidity of SUD is considered far more common among individuals with binge/purge type EDs, evidenced by a meta-analysis finding higher rates of comorbid SUD among patients with AN-BP and BN than AN-R [ 44 ]. This trend was also observed in population data [ 116 ]. Further, a multi-site study found that patients with BN had higher rates of comorbid SUD than patients with AN, BED and Eating Disorder Not Otherwise Specific (EDNOS) (utilised DSM-IV criteria) [ 117 ]. Behaviourally, there was an association between higher frequencies of binge/purge behaviours with high rates of substance use [ 117 ]. The higher risk of substance abuse among patients with binge/purge symptomology was also associated with younger age of binge eating onset [ 118 ]. A study explored whether BN and ED subtypes with binge/purge symptoms predicted adverse outcomes and found that adolescent girls with purging disorder were significantly more likely to use drugs or frequently binge drink [ 119 ]. This association was again observed in a network analysis of college students, whereby there was an association between binge drinking and increased ED cognitions [ 120 ].

Psychosis and schizophrenia

The RR identified a small body of literature with mixed results regarding the comorbidity of ED and psychosis-spectrum symptoms. A study of patients with schizophrenia found that 12% of participants met full diagnostic criteria for NES, with a further 10% meeting partial criteria [ 45 ]. Miotto and colleagues’ (2010) study noted higher rates of paranoid ideation and psychotic symptoms in ED patients than those observed in healthy controls [ 121 ]. However, the authors concluded that these symptoms were better explained by the participant's ED diagnosis than a psychotic disorder [ 121 ]. At a large population level, an English national survey noted associations between psychotic-like experiences and uncontrolled eating, food dominance and potential EDs [ 122 ]. In particular, these associations were stronger in males [ 122 ]. However, the true comorbidity between psychotic disorders and ED remains unclear and further research is needed.

Body dysmorphic disorder

While body image disturbances common to AN, BN and BED are primarily related to weight and shape concerns, individuals with body dysmorphic disorder (BDD) have additional concerns regarding other aspects of their appearance, such as facial features and skin blemishes [ 46 , 123 ]. AN and BDD share similar psychopathology and both have a peak onset period in adolescence, although BDD development typically precedes AN [ 46 ]. The prevalence rates of BDD among individuals with AN are variable. In one clinical sample of female AN patients, 26% met BDD diagnostic criteria [ 124 ]. However, much higher rates were observed in another clinical sample of adults with AN, where 62% of patients reported clinically significant 'dysmorphic concern' [ 125 ].

As the RR has found with other mental health comorbidities, BDD contributes to greater symptom severity in individuals with AN, making the disorder more difficult to treat. However, some research suggested that improved long-term outcomes from treatments for AN are associated with the integration of strategies that address dysmorphic concerns [ 124 , 126 ]. However, there remains little research on the similarities, differences and co-occurrence of BDD and AN, and with even less research on the cooccurrence of BDD and other EDs.

Neurodevelopmental disorders

Attention deficit hyperactivity disorder

Several studies noted the comorbidity between Attention Deficit Hyperactivity Disorder (ADHD) and EDs. A systematic review found moderate evidence for a positive association between ADHD and disordered eating, particularly between overeating and ADHD [ 47 ]. The impulsivity symptoms of ADHD were particularly associated with BN for all genders, and weaker evidence was found for the association between hyperactivity and restrictive EDs (AN and ARFID) for males, but not females [ 47 ]. Another meta-analysis reported a two-fold increased risk of ADHD in individuals with an ED [ 48 ] and studies have noted particularly strong associations between ADHD and BN [ 49 , 50 ]. In a cohort of adults with a diagnosis of an ED, 31.3% had a 'possible' ADHD [ 127 ]. Another study considered sex differences; women with ADHD had a significantly higher lifetime prevalence of both AN and BN than women without ADHD [ 128 ]. Further, the comorbidity rates for BED were considerably higher among individuals with ADHD for both genders [ 128 ].

Further evidence for a significant association between ADHD and EDs was reported in a population study of children [ 51 ]. Results revealed that children with ADHD were more like to experience an ED or binge, purge, or restrictive behaviours above clinical threshold [ 51 ]. Another study of children with ADHD considered gender differences; boys with ADHD had a greater risk of binge eating than girls [ 129 ]. However, the study found no significant difference in AN's prevalence between ADHD and non-ADHD groups. Further, among patients attending an ED specialist clinic, those with comorbid ADHD symptoms had poorer outcomes at one-year follow-up [ 130 ].

Autism spectrum disorder

There is evidence of heightened prevalence rates of autism spectrum disorder (ASD) among individuals with EDs. A systematic review found an average prevalence of ASD with EDs of 22.9% compared with 2% observed in the general population [ 52 ]. With regards to AN, several studies have found symptoms of ASD to be frequently exhibited by patients with AN [ 53 , 54 ]. An assessment of common phenomena between ARFID and ASD in children found a shared symptom profile of eating difficulties, behavioural problems and sensory hypersensitivity beyond what is observed in typically developing children (the control group) [ 55 ]. While research in this area is developing, the findings indicated these comorbidities would likely have implications for the treatment and management of both conditions [ 55 ].

Post traumatic stress disorder

Many individuals with EDs report historical traumatic experiences, and for a proportion of the population, symptoms of post traumatic stress disorder (PTSD). A broad range of prevalence rates between PTSD and EDs have been reported; between 16.1–22.7% for AN, 32.4–66.2% for BN and 24.02–31.6% for BED [ 56 ]. A review noted self-criticism, low self-worth, guilt, shame, depression, anxiety, emotion dysregulation, anger and impulsivity were linked to the association between EDs and trauma [ 57 ]. It was suggested that for individuals with trauma/PTSD, EDs might have a functional role to manage PTSD symptoms and reduce negative affect [ 57 ]. Further, some ED behaviours such as restriction, binge eating, and purging may be used to avoid hyperarousal, in turn maintaining the association between EDs and PTSD [ 57 ].

Few studies have explored the impact of comorbid PTSD on ED treatment outcomes. A study of inpatients admitted to a residential ED treatment service investigated whether PTSD diagnosis at admission was associated with symptom changes [ 56 ]. Cognitive and behavioural symptoms related to the ED had decreased at discharge, however, they increased again at six-month follow up. In contrast, while PTSD diagnosis was associated with higher baseline ED symptoms, it was not related to symptom change throughout treatment or treatment dropout [ 56 ]. Given previous research identified that PTSD and EDs tend to relate to more complex courses of illness, greater rates of drop out and poorer outcomes, a study by Brewerton and colleagues [ 131 ], explored the presence of EDs in patients with PTSD admitted to a residential setting. Results showed that patients with PTSD had significantly higher scores of ED psychopathology, as well as depression, anxiety and quality of life. [ 131 ]. Further, those with PTSD had a greater tendency for binge-type EDs.

Suicidality

Suicide is one of the leading causes of death for individuals with EDs [ 58 ]. In a longitudinal study of adolescents, almost one quarter had attempted suicide, and 65% reported suicidal ideation within the past 6 months [ 37 ]. EDs are a significant risk factor for suicide, with some evidence suggesting a genetic association between suicide risk and EDs [ 59 , 60 ]. This association was supported in the analysis of Swedish population registry data, which found that individuals with a sibling with an ED had an increased risk of suicide attempts with an odds ratio of 1.4 (relative cohort n  = 1,680,658) [ 61 ]. For suicide attempts, this study found an even higher odds ratio of 5.28 (relative cohort n  = 2,268,786) for individuals with an ED and 5.39 (relative cohort n  = 1,919,114) for death by suicide [ 61 ]. A comparison of individuals with AN and BN indicated that risk for suicide attempts was higher for those with BN compared to AN [ 61 ]. However, the opposite was true for death by suicide; which was higher in AN compared to BN [ 61 ]. This result is consistent with the findings of a meta-analysis—the incidence of suicide was higher among patients with AN compared to those with BN or BED [ 62 ].

The higher incidence of suicide in adults with AN [ 132 ] is potentially explained by the findings from Guillaume and colleagues (2011), which suggested that comparative to BN, AN patients are more likely to have more serious suicide attempts resulting in a higher risk of death [ 133 ]. However, death by suicide remains a significant risk for both diagnoses. As an example, Udo and colleagues (2019) study reported that suicide attempts were more common in those with an AN-BP subtype (44.1%) than AN-R (15.7%), or BN (31.4%) [ 134 ]. Further, in a large cohort of transgender college students with EDs, rates of past-year suicidal ideation (a significant risk factor for suicide attempts) was 75.2%, and suicide attempts were 74.8%, significantly higher than cisgender students with EDs and transgender students without EDs [ 135 ]. The RR found that the risk of suicidal ideation and behaviour was associated with ED diagnosis and the presence of other comorbidities. Among a community-based sample of female college students diagnosed with an ED, 25.6% reported suicidal ideation, and this was positively correlated with depression, anxiety and purging [ 136 ]. In support of this evidence, Sagiv and Gvion (2020) proposed a dual pathway model of risk of suicide attempt in individuals with ED, which implicates trait impulsivity and comorbid depression [ 137 ]. In two large transdiagnostic ED patient samples, suicidal ideation was associated with different aspects of self-image between ED diagnoses. For example, suicidal ideation was associated with higher levels of self-blame among individuals with BED, while among patients with AN and OSFED, increased suicidal ideation was associated with a lack of self-love [ 138 , 139 ].

Anorexia nervosa

Amongst adults with AN, higher rates of suicide have been reported amongst those with a binge-purge subtype (25%) than restrictive subtype (8.65%) [ 58 , 140 ]. Further, comorbid depression and prolonged starvation were strongly associated with elevated suicide attempts for both subtypes [ 58 , 140 ]. In another study, the risk of attempted suicide was associated with depression, but it was moderated by hospital treatment [ 93 ]. Further, suicidal ideation was related to depression. A significant 'acquired' suicide risk in individuals with AN has been identified by Selby et al. (2010) through an increased tolerance for pain and discomfort resultant from repeated exposure to painful restricting and purging behaviours [ 141 ].

Bulimia nervosa

Further research among individuals diagnosed with BN found an increased level of suicide risk [ 142 ]. Results from an extensive study of women with BN indicated that the lifetime prevalence of suicide attempts in this cohort was 26.9% [ 143 ]. In one study of individuals diagnosed with severe BN, 60% of deaths were attributed to suicide [ 144 ]. The mean age at the time of death was 29.6 years, and predictive factors included previous suicide attempts and low BMI. Further, in a sample of children and adolescents aged 7 to 18 years, higher rates of suicidal ideation were associated with BN, self-induced vomiting and a history of trauma [ 12 ].

A large population-based study of adolescents and adults explored the frequency and correlates of suicidal ideation and attempts in those who met the criteria for BN [ 145 ]. Suicidal ideation was highest in adolescents with BN (53%), followed by BED (34.4%), other non-ED psychopathology (21.3%) or no psychopathology (3.8%). A similar trend was observed for suicide plans and attempts [ 145 ]. However, for adults, suicidality was more prevalent in the BN group compared to no psychopathology, but not statistically different to the AN, BED or other psychopathology groups [ 145 ].

Consistent with Crow and colleagues’ (2014) results, in a sample of women with BN, depression had the strongest association with lifetime suicide attempts [ 146 ]. There were also associations between identity problems, cognitive dysregulation, anxiousness, insecure attachment and lifetime suicide attempts among the sample. Depression was the most pertinent association, suggesting that potential comorbid depression should be a focus of assessment and treatment among individuals with BN due to the elevated suicide risk for this group [ 146 ]. Insecure attachment is associated with childhood trauma, and a systematic review found that suicide attempts in women with BN were significantly associated with childhood abuse and familial history of EDs [ 58 ].

Binge eating disorder

The RR found mixed evidence for the association between suicidal behaviour and BED. A meta-analysis found no suicides for patients with BED [ 62 ]. However, evidence from two separate large national surveys found that a significant proportion of individuals who had a suicide attempt also had a diagnosis of BED [ 134 , 147 ].

Non-suicidal self injury

Non-suicidal self-injury (NSSI), broadly defined, is the intentional harm inflicted to one’s body without intent to die [ 148 ]. Recognising NSSI is often a precursor for suicidal ideation and behaviour [ 149 ], together with the already heightened mortality rate for EDs, several studies have examined the association between EDs and NSSI. Up to one-third of patients with EDs report NSSI at some stage in their lifetime, with over one quarter having engaged in NSSI within the previous year [ 63 ]. Similarly, a cohort study [ 148 ] found elevated rates of historical NSSI amongst patients with DSM-IV EDs; specifically EDNOS (49%), BN (41%) and AN (26%). In a Spanish sample of ED patients, the most prevalent form of NSSI was banging (64.6%) and cutting (56.9%) [ 63 ].

Further research has explored the individual factors associated with heightened rates of NSSI. Higher levels of impulsivity among patients with EDs have been associated with concomitant NSSI [ 64 ]. This was demonstrated in a longitudinal study of female students, whereby NSSI preceded purging, marking it a potential risk factor for ED onset [ 65 ]. In a study of a large clinical sample of patients with EDs and co-occurring NSSI, significantly higher levels of emotional reactivity were observed [ 150 ]. The highest levels of emotional reactivity were reported by individuals with a diagnosis of BN, who were also more likely to engage in NSSI than those with AN [ 150 ]. In Olatunji and colleagues’ (2015) cohort study, NSSI was used to regulate difficult emotions, much like other ED behaviours. NSSI functioning as a means to manage negative affect associated with EDs was further supported by Muehlenkamp and colleagues’ [ 66 ] study exploring the risk factors in inpatients admitted for an ED. The authors found significant differences in the prevalence of NSSI across ED diagnoses, although patients with binge/purge subtype EDs were more likely to engage in poly-NSSI (multiple types of NSSI). Consistent with these findings, a study of patients admitted to an ED inpatient unit found that 45% of patients displayed at least one type of NSSI [ 151 ]. The function of NSSI among ED patients was explored in two studies, one noting that avoiding or suppressing negative feelings was the most frequently reported reason for NSSI [ 151 ]. The other analysed a series of interviews and self-report questionnaires and found patients with ED and comorbid Borderline Personality Disorder (BPD) engaged in NSSI as a means of emotion regulation [ 152 ].

Medical comorbidities

The impact of EDs on physical health and the consequential medical comorbidities has been a focus of research. Many studies reported medical comorbidities resulting from prolonged malnutrition, as well as excessive exercise, binging and purging behaviours.

Cardiovascular complications

As discussed above, although suicide is a significant contributor to the mortality rate of EDs, physical and medical complications remain the primary cause of death, particularly in AN, with a high proportion of deaths thought to result from cardiovascular complications [ 153 ]. AN has attracted the most research focus given its increased risk of cardiac failure due to severe malnutrition, dehydration and electrolyte imbalances [ 67 ].

Cardiovascular complications in AN can be divided by conduction, structural and ischemic diseases. A review found that up to 87% of patients experience cardiovascular compromise shortly following onset of AN [ 153 ]. Within conduction disease, bradycardia and QT prolongation occur at a high frequency, largely due to low body weight and resultant decreased venous return to the heart. Whereas, atrioventricular block and ventricular arrhythmia are more rare [ 153 ]. Various structural cardiomyopathies are observed in AN, such as low left ventricular mass index (occurs frequently), mitral prolapse and percardial effusion (occurs moderately). Ischemic diseases such as dyslipidemia or acute myocardial infarction are more rare.

Another review identified cardiopulmonary abnormalities that are frequently observed in AN; mitral valve prolapse occurred in 25% of patients, sinus bradycardia was the most common arrhythmia, and pericardial effusion prevalence rates ranged from 15 to 30%. [ 68 ] Sudden cardiac death is thought to occur due to increased QT interval dispersion and heart rate variability. [ 68 ] A review of an inpatient database in a large retrospective cohort study found that coronary artery disease (CAD) was lower in AN patients than the general population (4.4% and 18.4%, respectively). Consistent with trends in the general population, the risk of cardiac arrest, arrhythmias and heart failure was higher in males with AN than females with AN [ 69 ].

Given that individuals with AN have compromised biology, may avoid medical care, and have higher rates of substance use, research has examined cancer incidence and prognosis among individuals with AN. A retrospective study noted higher mortality from melanoma, cancers of genital organs and cancers of unspecified sites among individuals with AN, however, there was no statistically significant difference compared to the general population [ 70 ]. No further studies of cancer in EDs were identified.

Gastrointestinal disorders

The gastrointestinal (GI) system plays a pivotal role in the development, maintenance, and treatment outcomes for EDs, with changes and implications present throughout the GI tract. More than 90% of AN patients report fullness, early satiety, abdominal distention, pain and nausea [ 68 ]. Although it is well understood that GI system complaints are complicated and exacerbated by malnutrition, purging and binge eating [ 154 , 155 ], the actual cause of the increased prevalence of GI disorders and their contribution to ED maintenance remain poorly understood.

To this end, a review aimed to determine the GI symptoms reported in two restrictive disorders (AN and ARFID), as well as the physiologic changes as a result of malnutrition and function of low body weight and the contribution of GI diseases to the disordered eating observed in AN and ARFID [ 156 ]. The review found mixed evidence regarding whether GI issues were increased in patients with AN and ARFID. This was partly due to the relatively limited amount of research in this area and mixed results across the literature. The review noted that patients with AN and ARFID reported a higher frequency of symptoms of gastroparesis. Further, there was evidence for a bidirectional relationship between AN and functional gastrointestinal disorders (FGIDs) contributing to ongoing disordered eating. The review found that GI symptoms observed in EDs develop due to (1) poorly treated medical conditions with GI-predominant symptoms, (2) the physiological and anatomical changes that develop due to malnutrition or (3) FGIDs.

There was a high rate of comorbidity (93%) between ED and FGIDs, including oesophageal, bowel and anorectal disorders, in a patient sample with AN, BN and EDNOS [ 157 ]. A retrospective study investigating increased rates of oesophageal cancer in individuals with a history of EDs could not conclude that risk was associated with purging over other confounding factors such as alcohol abuse and smoking [ 158 ].

Given that gut peptides like ghrelin, cholecystokinin (CCK), peptide tyrosine (PYY) and glucagon-like peptide 1 (GLP-1) are known to influence food intake, attention has focussed on the dysregulation of gut peptide signalling in EDs [ 159 ]. A review aimed to discuss how these peptides or the signals triggered by their release are dysregulated in EDs and whether they are normalised following weight restoration or weight loss (in the case of people with higher body weight) [ 159 ]. The results were inconsistent, with significant variability in peptide dysregulation observed across EDs [ 159 ]. A systematic review and meta-analysis explored whether ghrelin is increased in restrictive AN. The review found that all forms of ghrelin were raised in AN’s acute state during fasting [ 160 ]. In addition, the data did not support differences in ghrelin levels between AN subtypes [ 160 ]. Another study examined levels of orexigenic ghrelin and anorexigenic peptide YY (PYY) in young females with ARFID, AN and healthy controls (HC) [ 161 ]. Results demonstrated that fasting and postprandial ghrelin were lower in ARFID than AN, but there was no difference between ARFID and AN for fasting and postprandial PYY [ 161 ].

Oesophageal and gastrointestinal dysfunction have been observed in patients with AN and complicate nutritional and refeeding interventions [ 155 ]. Findings from a systematic review indicated that structural changes that occurred in the GI tract of patients with AN impacted their ability to swallow and absorb nutrients [ 162 ]. Interestingly, no differences in the severity of gastrointestinal symptoms were observed between AN-R and AN-BP subtypes [ 155 ].

A systematic review of thirteen studies aimed to identify the most effective treatment approaches for GI disorders and AN [ 163 ]. An improvement in at least one or more GI symptoms was reported in 11 of the 13 studies, with all studies including nutritional rehabilitation, and half also included concurrent psychological treatment [ 163 ]. Emerging evidence on ED comorbidity with chronic GI disorders suggested that EDs are often misdiagnosed in children and adolescents due to the crossover of symptoms. Therefore, clinicians treating children and adolescents for GI dysfunction should be aware of potential EDs and conduct appropriate screening [ 164 ]. There has been an emerging focus on the role of the gut microbiome in the regulation of core ED symptoms and psychophysiology. Increased attention is being paid to how the macronutrient composition of nutritional rehabilitation should be considered to maximise treatment outcomes. A review found that high fibre consumption in addition to prebiotic and probiotic supplementation helped balance the gut microbiome and maintained the results of refeeding [ 165 ].

Bone health

The RR found evidence for bone loss/poor bone mineral density (BMD) and EDs, particularly in AN. The high rates of bone resorption observed in patients with AN is a consequence of chronic malnutrition leading to osteoporosis (weak and brittle bones), increased fracture risk and scoliosis [ 166 ]. The negative impacts of bone loss are more pronounced in individuals with early-onset AN when the skeleton is still developing [ 67 ] and among those who have very low BMI [ 71 ], with comorbidity rates as high as 46.9% [ 71 ]. However, lowered BMD was also observed among patients with BN [ 72 ].

A review [ 167 ] explored the prevalence and differences in pathophysiology of osteoporosis and fractures in patients with AN-R and AN-BP. AN-R patients had a higher prevalence of osteoporosis, and AN-BP patients had a higher prevalence of osteopenia (loss of BMD) [ 167 ]. Further, the authors noted the significant increase in fracture risk that starts at disease onset and lasts throughout AN, with some evidence that risk remains increased beyond remission and recovery [ 167 ]. Findings from a longitudinal study of female patients with a history of adolescent AN found long-term bone thinning at five and ten-year follow-up despite these patients achieving weight restoration [ 168 ].

Given this, treatment to increase BMD in individuals with AN has been the objective of many pharmacotherapy trials, mainly investigating the efficacy of hormone replacement [ 169 , 170 ]. Treatments include oestrogen and oral contraceptives [ 169 , 170 , 171 , 172 ]; bisphosphonates [ 169 , 173 ]; other hormonal treatment [ 174 , 175 , 176 , 177 ] and vitamin D [ 178 ]. However, the outcomes of these studies were mixed.

Refeeding syndrome

Nutritional rehabilitation of severely malnourished individuals is central to routine care and medical stabilisation of patients with EDs [ 179 ]. Within inpatient treatment settings, reversing severe malnutrition is achieved using oral, or nasogastric tube feeding. However, following a period of starvation, initiating/commencing feeding has been associated with ‘refeeding syndrome’ (RFS), a potentially fatal electrolyte imbalance caused by the body's response to introducing nutritional restoration [ 180 , 181 ]. The studies identified in the RR focused predominantly on restrictive EDs/on this population group—results regarding RFS risk were mixed [ 73 ].

A retrospective cohort study of inpatients diagnosed with AN with a very low BMI implemented a nasogastric feeding routine with vitamin, potassium and phosphate supplementation [ 182 ]. All patients achieved a significant increase in body weight. None developed RFS [ 182 ], suggesting that even with extreme undernutrition, cautious feeding within a specialised unit can be done safely without RFS. For adults with AN, aminotransferases are often high upon admission, however are normalised following four weeks of enteral feeding [ 183 , 184 ]. Further, the RR identified several studies demonstrating the provision of a higher caloric diet at intake to adolescents with AN led to faster recoveries and fewer days in the hospital with no observed increased risk for RFS [ 75 , 76 , 77 ]. These findings were also noted in a study of adults with AN [ 179 ].

However, the prevalence of RFS among inpatients is highly variable, with one systematic review noting rates ranging from 0 to 62% [ 74 ]. This variability was largely a reflection of the different definitions of RFS used across the literature [ 74 ]. A retrospective review of medical records of patients with AN admitted to Intensive Care Units (ICUs) aimed to evaluate complications, particularly RFS, that occurred during the ICU stay and the impact of these complications on treatment outcomes [ 185 ]. Of the 68 patients (62 female), seven developed RFS (10.3%) [ 185 ].

Although easily detectable and treatable, hypophosphatemia (a low serum phosphate concentration) may lead to RFS which is the term used to describe severe fluid and electrolyte shifts that can occur when nutrition support is introduced after a period of starvation. Untreated hypophosphatemia may lead to characteristic signs of the RFS such as respiratory failure, heart failure, and seizures [ 76 , 179 , 186 , 187 , 188 ]. A retrospective case–control study of inpatients with severe AN identified [ 189 ]. A retrospective study of AN and atypical AN patients undergoing refeeding found that the risk of hypophosphatemia was associated with a higher level of total weight loss and recent weight loss rather than the patient’s weight at admission [ 190 ]. The safe and effective use of prophylactic phosphate supplementation during refeeding was supported by the results from Agostino and colleagues’ chart review study [ 191 ], where 90% of inpatients received supplementation during admission.

Higher calorie refeeding approaches are considered safe in most cases, however the steps necessitated to monitor health status are costly to health services [ 192 ]. The most cost-effective approach would likely involve prophylactic electrolyte supplementation in addition to high calorie refeeding, which would decrease the need for daily laboratory monitoring as well as shortening hospital stays [ 75 , 191 , 192 ]. A systematic review noted that much of the research regarding refeeding, particularly in children and young people, has been limited by small sample sizes, single-site studies and heterogeneous designs [ 181 ]. Further, the differing definitions of RFS, recovery, remission and outcomes leading to variable results. While RFS appears safe for many people requiring feeding, the risk and benefits of it are unclear [ 193 ] due to the limited research on this topic. Following current clinical practice guidelines on the safe introduction of nutrition is recommended.

Metabolic syndrome

Metabolic syndrome refers to a group of factors that increase risks for heart disease, diabetes, stroke and other related conditions [ 194 ]. Metabolic syndrome is conceptualised as five key criteria; (1) elevated waist circumference, (2) elevated triglyceride levels, (3) reduced HDL-C, (4) elevated blood pressure and (5) elevated fasting glucose. The binge eating behaviours exhibited in BN, BED and NES have been linked to the higher rates of metabolic syndrome observed in these ED patients [ 78 , 195 ].

An analysis of population data of medical comorbidities with BED noted the strongest associations were with diabetes and circulatory systems, likely indexing components of metabolic syndrome [ 196 ]. While type 1 diabetes is considered a risk factor for ED development, both BN and BED have increased risk for type 2 diabetes [ 78 ]. A 16-year observation study found that the risk of type 2 diabetes was significantly increased in male patients with BED compared to the community controls [ 78 ]. By the end of the observation period, 33% of patients with BED had developed type 2 diabetes compared to 1.7% of the control group. The prevalence of type 2 diabetes among patients with BN was also slightly elevated at 4.4% [ 78 ]. Importantly, the authors were not able to control for BMI in this study. In another study, BED was the most prevalent ED in a cohort of type 2 diabetes patients [ 197 ]. Conversely, the prevalence of AN among patients with type 2 diabetes is significantly lower, with a review of national data reporting comorbidity rates to be 0.06% [ 198 ].

Metabolic dysfunction was observed in a relatively large sample of individuals with NES, including metabolic syndrome and type 2 diabetes, with women reporting slightly higher rates (13%) than men (11%) [ 199 ]. In another group of adults with type 2 diabetes, 7% met the diagnostic criteria for NES [ 200 ]. These findings suggested a need for increased monitoring and treatment of type 2 diabetes in individuals with EDs, particularly BED and NES. Another study found BED had a significant impact on metabolic abnormalities, including elevated cholesterol and poor glycaemic control [ 201 ].

The RR identified one intervention study, which examined an intervention to address medical comorbidities associated with BN and BED [ 195 ]. The study compared cognitive behaviour therapy (CBT) to an exercise and nutrition intervention to increase physical fitness, decrease body fat percentage and reduce the risk for metabolic syndrome. While the exercise intervention improved participants' physical fitness and body composition, neither group reduced cardiovascular risk at one-year follow-up [ 195 ].

Oral health

Purging behaviour, particularly self-induced vomiting, has been associated with several oral health and gastrointestinal dysfunctions in patients with EDs. A case–control study of ED patients with binge/purge symptomology found that despite ED patients reporting an increased concern for dental issues and engaging in more frequent brushing, their oral health was poorer than controls. [ 79 ] Further, a systematic review and meta-analysis aimed to explore whether EDs increase the risk of tooth erosion [ 80 ]. The analysis found that patients with EDs had more risk of dental erosion, especially among those who self-induced vomiting [ 80 ]. These findings were also found in a large cohort study, where the increased risk for BN was associated with higher rates of dental erosion but not dental cavities [ 81 ].

However, a systematic review of 10 studies suggested that poor oral health may be common among ED patients irrespective of whether self-induced vomiting forms part of their psychopathology [ 202 ]. One study reported that AN-R patients had poorer oral health outcomes and tooth decay than BN patients [ 203 ]. Two studies identified associations between NES and poor oral health, including higher rates of missing teeth, periodontal disease [ 204 , 205 ]. Another study of a group of patients with AN, BN and EDNOS, demonstrated the impact of ED behaviours on dental soft tissue, whereby 94% of patients had oral mucosal lesions, and 3% were found to have dental erosion [ 206 ].

Vitamin deficiencies

The prolonged periods of starvation, food restriction (of caloric intake and/or food groups), purging and excessive exercise observed across the ED spectrum have detrimental impacts on micronutrient balances [ 207 ]. The impact of prolonged vitamin deficiencies in early-onset EDs can also impair brain development, substantially reducing neurocognitive function in some younger patients even after weight restoration [ 82 ]. Common micronutrient deficiencies include calcium, fat soluble vitamins, essential fatty acids selenium, zinc and B vitamins [ 183 ]. One included study looked at prevalence rates of cerebral atrophy and neurological conditions, specifically Wernicke's encephalopathy in EDs and found that these neurological conditions were very rare in people with EDs [ 208 ].

Cognitive functioning

The literature included in RR regarding the cognitive changes in ED patients with AN following weight gain was sparse. It appears that some cognitive functions affected by EDs recover following nutritional restoration, whereas others persist. Cognitive functions, such as flexibility, central coherence, decision making, attention, processing speed and memory, are hypothesised to be impacted by, and influence the maintenance of EDs. A systematic review explored whether cognitive functions improved in AN following weight gain [ 83 ]. Weight gain appeared to be associated with improved processing speed in children and adolescents. However, no improvement was observed in cognitive flexibility following weight gain. Further, the results for adults were inconclusive [ 83 ].

Reproductive health

Infertility and higher rates of poor reproductive health are strongly associated with EDs, including miscarriages, induced abortions, obstetric complications, and poorer birth outcomes [ 84 , 85 ]. Although amenorrhea is a known consequence of AN, oligomenorrhea (irregular periods) was common among individuals with BN and BED [ 86 ]. A twin study found women diagnosed with BN and BED were also more likely to have poly cystic ovarian syndrome (PCOS), leading to menstrual irregularities [ 209 ]. The prevalence of lifetime amenorrhea in this sample was 10.4%, and lifetime oligomenorrhea was 33.7%. An epidemiological study explored the association of premenstrual syndrome (PMS) and premenstrual dysphoric disorder (PMDD) in women with BN and BED and found prevalence rates as high as 42.4% for PMS and 4.2% for PMDD [ 210 ].

Given the increased rates of menstrual irregularities and issues, questions have been raised regarding whether this complication is reversed or improves with recovery. A review of five studies monitoring reproductive functions during recovery over a 6- to 18-year follow up period [ 211 ] noted no significant difference between the pooled odds of childbirth rates between the AN and general population—demonstrating that if patients undergo treatment for AN, achieve weight restoration, and continue to maintain wellness, reproductive functions can renormalise [ 211 ].

An observational study of women with AN, BN or EDNOS found higher rates of low birth rate, pre-term deliveries, caesarean deliveries, and intrauterine growth restrictions [ 84 ]. Increased caesarean delivery was also observed in a large cohort of women diagnosed with BED [ 212 ]. However, these women had higher birth weight babies [ 212 ]. Further, women with comorbid ED and epilepsy were found to have an increased risk of pregnancy-related comorbidities, including preeclampsia (gestational hypertension and signs of damage to the liver and kidneys ) , gestational diabetes and perinatal depression [ 213 ].

The results from this review identified that the symptomology and outcomes of EDs are impacted by both psychiatric and medical factors. Further, EDs have a mortality rate substantially higher than the general population, with a significant proportion of those who die from an ED dying by suicide or as a result of severe medical complications.

This RR noted high rates of psychiatric and medical comorbidities in people with EDs, with comorbidities contributing to increased ED symptom severity, maintenance of some ED behaviours, compromised functioning, and adverse treatment outcomes. Evidence suggested that early identification and management of psychiatric and medical comorbidities in people with an ED may improve response to treatment and outcomes [ 29 , 35 , 83 ].

EDs and other psychiatric conditions often shared symptoms and high levels of psychopathology crossover were noted. The most prevalent psychiatric comorbidities were anxiety disorders, mood disorders and substance use disorders [ 8 , 100 , 119 ]. perhaps unsurprising given the prevalence of these illnesses in the general population. Of concern is the elevated suicide rate noted across the ED spectrum, the highest observed in AN [ 58 , 140 , 149 ]. For people with AN, suicide attempts were mostly associated with comorbid mood and anxiety disorders [ 136 ]. The review noted elevated rates of NSSI were particularly associated with binge/purge subtype EDs [ 150 ], impulsivity and emotional dysregulation (again, an example of psychopathological overlap).

With regards to PDs, studies were limited to EDs with binge-purge symptomology. Of those included, the presence of a comorbid personality disorder and ED was associated with childhood trauma [ 110 ] and elevated mortality risk [ 111 ]. There appeared to be a link between the clinical characteristics of the ED (e.g., impulsivity, rigidity) and the comorbid PD (cluster B PDs were more associated with BN/BED and cluster C PDs were more associated with AN). There was mixed (albeit limited) evidence regarding the comorbidity between EDs and psychosis and schizophrenia, with some studies noting an association between EDs and psychotic experiences [ 45 ]. Specifically, there was an association between psychotic experiences and uncontrolled eating and food dominance, which were stronger in males [ 122 ]. In addition, the review noted the association between EDs and neurodevelopmental disorders-specifically ADHD—was associated with features of BN and ASD was more prevalent among individuals with AN [ 53 , 54 ] and ARFID [ 55 ].

EDs are complicated by medical comorbidities across the neuroendocrine, skeletal, nutritional, gastrointestinal, dental, and reproductive systems that can occur alongside, or result from the ED. The RR noted mixed evidence regarding the effectiveness and safety of enteral feeding [ 180 , 181 ], with some studies noting that RFS could be safely managed with supplementation [ 191 ]. Research also described the impacts of restrictive EDs on BMD and binge eating behaviour on metabolic disorders [ 78 , 195 ]. Purging behaviours, particularly self-induced vomiting [ 79 ], were found to increase the risk of tooth erosion [ 81 ] and damage to soft tissue within the gastrointestinal tract [ 206 ]. Further, EDs were associated with a range of reproductive health issues in women, including infertility and birth complications [ 84 ].

Whilst the RR achieved its aim of synthesising a broad scope of literature, the absence of particular ED diagnoses and other key research gaps are worth noting. A large portion of the studies identified focused on AN, for both psychiatric and medical comorbidities. This reflects the stark lack of research exploring the comorbidities for ARFID, NES, and OSFED compared to that seen with AN, BN and BED. There were no studies identified exploring the psychiatric and medical comorbidities of Pica. These gaps could in part be due to the timeline utilised in the RR search strategy, which included the transition from DSM-IV to DSM-5. The update in the DSM had significant implications for psychiatric diagnosis, with the addition of new disorders (such as Autism Spectrum Disorder and various Depressive Disorders), reorganisation (for example, moving OCD and PTSD out of anxiety disorders and into newly defined chapters) and changes in diagnostic criteria (including for AN and BN, and establishing BED as a discrete disorder). Although current understanding suggests EDs are more prevalent in females, research is increasingly demonstrating that males are not immune to ED symptoms, and the RR highlighted the disproportionate lack of male subjects included in recent ED research, particularly in the domain of psychiatric and medical comorbidities.

As the RR was broad in scope and policy-driven in intent, limitations as a result of this methodology ought to be considered. The RR only considered ‘Western’ studies, leading to the potential of important pieces of work not being included in the synthesis. In the interest of achieving a rapid synthesis, grey literature, qualitative and theoretical works, case studies or implementation research were not included, risking a loss of nuance in developing fields, such as the association and prevalence of complex/developmental trauma with EDs (most research on this comorbidity focuses on PTSD, not complex or developmental trauma) or body image dissatisfaction among different gender groups. No studies regarding the association between dissociative disorders and EDs were included in the review. However, dissociation can co-occur with EDs, particularly AN-BP and among those with a trauma history [ 214 ]. Future studies would benefit from exploring this association further, particularly as trauma becomes more recognised as a risk factor for ED development.

The review was not designed to be an exhaustive summary of all medical comorbidities. Thus, some areas of medical comorbidity may not be included, or there may be variability in the level of detail included (such as, limited studies regarding the association between cancer and EDs). Studies that explored the association between other autoimmune disorders (such as Type 1 Diabetes, Crohn’s disease, Addison’s disease, ulcerative colitis, and coeliac disease) and EDs [ 215 , 216 ] were not included. Future reviews and research should examine the associations between autoimmune disorders and the subsequent increased risk of EDs, and likewise, the association between EDs and the subsequent risk of autoimmune disorders.

An important challenge for future research is to explore the impact of comorbidity on ED identification, development and treatment processes and outcomes. Insights could be gained from exploring shared psychiatric symptomology (i.e., ARFID and ASD, BN/BED and personality disorders, and food addiction). Particularly in disorders where the psychiatric comorbidity appears to precede the ED diagnosis (as may be the case in anxiety disorders [ 28 ]) and the unique physiological complications of these EDs (e.g., the impact of ARFID on childhood development and growth). Further, treatment outcomes would benefit from future research exploring the nature of the proposed reciprocal nature between EDs and comorbidities, particularly in those instances where there is significant shared psychopathology, or the presence of ED symptoms appears to exacerbate the symptoms of the other condition—and vice versa.

The majority of research regarding the newly introduced EDs has focused on understanding their aetiology, psychopathology, and what treatments demonstrate efficacy. Further, some areas included in the review had limited included studies, for example cancer and EDs. Thus, in addition to the already discussed need for further review regarding the association between EDs and autoimmune disorders, future research should explore the nature and prevalence of comorbidity between cancers and EDs. There was variability regarding the balance of child/adolescent and adult studies across the various comorbidities. Some comorbidities are heavily researched in child and adolescent populations (such as refeeding syndrome) and others there is stark child and adolescent inclusion, with included studies only looking at adult samples. Future studies should also address specific comorbidities as they apply to groups underrepresented in current research. This includes but is not limited to gender, sexual and racial minorities, whereby prevalence rates of psychiatric comorbidities are elevated. [ 88 ] In addition, future research would benefit from considering the nature of psychiatric and medical comorbidity for subthreshold and subclinical EDs, particularly as it pertains to an opportunity to identify EDs early within certain comorbidities where ED risk is heightened.

This review has identified the psychiatric and medical comorbidities of EDs, for which there is a substantial level of literature, as well as other areas requiring further investigation. EDs are associated with a myriad of psychiatric and medical comorbidities which have significant impacts on the symptomology and outcomes of an already difficult to treat, and burdensome illness.

Availability of data and materials

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Abbreviations

Anorexia nervosa—restricting type

Anorexia nervosa—binge-purge type

Avoidant restrictive food intake disorder

Body mass index

Borderline personality disorder

Diagnostic and statistical manual of mental disorders, 5th edition

Eating disorder

Generalised anxiety disorder

International classification of diseases, 11th edition

Major depressive disorder

Night eating syndrome

Other specified feeding or eating disorder

Post-traumatic stress disorder

Rapid review

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Acknowledgements

The authors would like to thank and acknowledge the hard work of Healthcare Management Advisors (HMA) who were commissioned to undertake the Rapid Review. Additionally, the authors would like to thank all members of the consortium and consultation committees for their advice, input, and considerations during the development process. Further, a special thank you to the carers, consumers and lived experience consultants that provided input to the development of the Rapid Review and wider national Eating Disorders Research & Translation Strategy. Finally, thank you to the Australian Government—Department of Health for their support of the current project.

National Eating Disorder Research Consortium: Phillip Aouad, Sarah Barakat, Robert Boakes, Leah Brennan, Emma Bryant, Susan Byrne, Belinda Caldwell, Shannon Calvert, Bronny Carroll, David Castle, Ian Caterson, Belinda Chelius, Lyn Chiem, Simon Clarke, Janet Conti, Lexi Crouch, Genevieve Dammery, Natasha Dzajkovski, Jasmine Fardouly, Carmen Felicia, John Feneley, Amber-Marie Firriolo, Nasim Foroughi, Mathew Fuller-Tyszkiewicz, Anthea Fursland, Veronica Gonzalez-Arce, Bethanie Gouldthorp, Kelly Griffin, Scott Griffiths, Ashlea Hambleton, Amy Hannigan, Mel Hart, Susan Hart, Phillipa Hay, Ian Hickie, Francis Kay-Lambkin, Ross King, Michael Kohn, Eyza Koreshe, Isabel Krug, Anvi Le, Jake Linardon, Randall Long, Amanda Long, Sloane Madden, Sarah Maguire, Danielle Maloney, Peta Marks, Sian McLean, Thy Meddick, Jane Miskovic-Wheatley, Deborah Mitchison, Richard O’Kearney, Shu Hwa Ong, Roger Paterson, Susan Paxton, Melissa Pehlivan, Genevieve Pepin, Andrea Phillipou, Judith Piccone, Rebecca Pinkus, Bronwyn Raykos, Paul Rhodes, Elizabeth Rieger, Sarah Rodan, Karen Rockett, Janice Russell, Haley Russell, Fiona Salter, Susan Sawyer, Beth Shelton, Urvashnee Singh, Sophie Smith, Evelyn Smith, Karen Spielman, Sarah Squire, Juliette Thomson, Marika Tiggemann, Stephen Touyz, Ranjani Utpala, Lenny Vartanian, Andrew Wallis, Warren Ward, Sarah Wells, Eleanor Wertheim, Simon Wilksch & Michelle Williams

The RR was in-part funded by the Australian Government Department of Health in partnership with other national and jurisdictional stakeholders. As the organisation responsible for overseeing the National Eating Disorder Research & Translation Strategy, InsideOut Institute commissioned Healthcare Management Advisors to undertake the RR as part of a larger, ongoing, project. Role of Funder: The funder was not directly involved in informing the development of the current review.

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School of Health and Social Development, Faculty of Health, Deakin University, Geelong, VIC, 3220, Australia

Genevieve Pepin

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National Eating Disorder Research Consortium

• Phillip Aouad
• , Sarah Barakat
• , Robert Boakes
• , Leah Brennan
• , Emma Bryant
• , Susan Byrne
• , Belinda Caldwell
• , Shannon Calvert
• , Bronny Carroll
• , David Castle
• , Ian Caterson
• , Belinda Chelius
• , Lyn Chiem
• , Simon Clarke
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• , Lexi Crouch
• , Genevieve Dammery
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• , Jasmine Fardouly
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• , John Feneley
• , Amber-Marie Firriolo
• , Nasim Foroughi
• , Mathew Fuller-Tyszkiewicz
• , Anthea Fursland
• , Veronica Gonzalez-Arce
• , Bethanie Gouldthorp
• , Kelly Griffin
• , Scott Griffiths
• , Ashlea Hambleton
• , Amy Hannigan
• , Susan Hart
• , Phillipa Hay
• , Ian Hickie
• , Francis Kay-Lambkin
• , Ross King
• , Michael Kohn
• , Eyza Koreshe
• , Isabel Krug
• , Jake Linardon
• , Randall Long
• , Amanda Long
• , Sloane Madden
• , Sarah Maguire
• , Danielle Maloney
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• , Sian McLean
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• , Richard O’Kearney
• , Shu Hwa Ong
• , Roger Paterson
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• , Andrea Phillipou
• , Judith Piccone
• , Rebecca Pinkus
• , Bronwyn Raykos
• , Paul Rhodes
• , Elizabeth Rieger
• , Sarah Rodan
• , Karen Rockett
• , Janice Russell
• , Haley Russell
• , Fiona Salter
• , Susan Sawyer
• , Beth Shelton
• , Urvashnee Singh
• , Sophie Smith
• , Evelyn Smith
• , Karen Spielman
• , Sarah Squire
• , Juliette Thomson
• , Marika Tiggemann
• , Stephen Touyz
• , Ranjani Utpala
• , Lenny Vartanian
• , Andrew Wallis
• , Warren Ward
• , Sarah Wells
• , Eleanor Wertheim
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Contributions

DM, PM, ST and SM oversaw the Rapid Review process; AL carried out and wrote the initial review; AH and GP wrote the first manuscript; all authors edited and approved the final manuscript.

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Correspondence to Ashlea Hambleton .

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ST receives royalties from Hogrefe and Huber, McGraw Hill and Taylor and Francis for published books/book chapters. He has received honoraria from the Takeda Group of Companies for consultative work, public speaking engagements and commissioned reports. He has chaired their Clinical Advisory Committee for Binge Eating Disorder. He is the Editor in Chief of the Journal of Eating Disorders. ST is a committee member of the National Eating Disorders Collaboration as well as the Technical Advisory Group for Eating Disorders. AL undertook work on this RR while employed by HMA. A/Prof Sarah Maguire is a guest editor of the special issue “Improving the future by understanding the present: evidence reviews for the field of eating disorders.”

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Additional file 1..

PRISMA diagram.

Additional file 2.

Studies included in the Rapid Review.

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Hambleton, A., Pepin, G., Le, A. et al. Psychiatric and medical comorbidities of eating disorders: findings from a rapid review of the literature. J Eat Disord 10 , 132 (2022). https://doi.org/10.1186/s40337-022-00654-2

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What improves access to primary healthcare services in rural communities? A systematic review

• Zemichael Gizaw 1 ,
• Tigist Astale 2 &
• Getnet Mitike Kassie 2  

BMC Primary Care volume  23 , Article number:  313 ( 2022 ) Cite this article

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To compile key strategies from the international experiences to improve access to primary healthcare (PHC) services in rural communities. Different innovative approaches have been practiced in different parts of the world to improve access to essential healthcare services in rural communities. Systematically collecting and combining best experiences all over the world is important to suggest effective strategies to improve access to healthcare in developing countries. Accordingly, this systematic review of literature was undertaken to identify key approaches from international experiences to enhance access to PHC services in rural communities.

All published and unpublished qualitative and/or mixed method studies conducted to improvement access to PHC services were searched from MEDLINE, Scopus, Web of Science, WHO Global Health Library, and Google Scholar. Articles published other than English language, citations with no abstracts and/or full texts, and duplicate studies were excluded. We included all articles available in different electronic databases regardless of their publication years. We assessed the methodological quality of the included studies using mixed methods appraisal tool (MMAT) version 2018 to minimize the risk of bias. Data were extracted using JBI mixed methods data extraction form. Data were qualitatively analyzed using emergent thematic analysis approach to identify key concepts and coded them into related non-mutually exclusive themes.

Our analysis of 110 full-text articles resulted in ten key strategies to improve access to PHC services. Community health programs or community-directed interventions, school-based healthcare services, student-led healthcare services, outreach services or mobile clinics, family health program, empanelment, community health funding schemes, telemedicine, working with traditional healers, working with non-profit private sectors and non-governmental organizations including faith-based organizations are the key strategies identified from international experiences.

This review identified key strategies from international experiences to improve access to PHC services in rural communities. These strategies can play roles in achieving universal health coverage and reducing disparities in health outcomes among rural communities and enabling them to get healthcare when and where they want.

Peer Review reports

Introduction

Universal health coverage (UHC) is used to provide expanding services to eliminate access barriers. Universal health coverage is defined by the world health organization (WHO) as access to key promotional, preventive, curative and rehabilitative health services for all at an affordable rate and ensuring equity in access. The term universal has been described as the State's legal obligation to provide healthcare to all its citizens, with particular attention to ensuring that all poor and excluded groups are included [ 1 , 2 , 3 ].

Strengthening primary healthcare (PHC) is the most comprehensive, reliable and productive approach to improving people's physical and mental wellbeing and social well-being, and that PHC is a pillar of a sustainable health system for UHC and health-related sustainable development goals [ 4 , 5 ]. Despite tremendous progress over the last decades, there are still unaddressed health needs of people in all parts of the world [ 6 , 7 ]. Many people, particularly the poor and people living in rural areas and those who are in vulnerable circumstances, face challenges to remain healthy [ 8 ].

Geographical and financial inaccessibility, inadequate funding, inconsistent medication supply and equipment and personnel shortages have left the reach, availability and effect of PHC services in many countries disappointingly limited [ 9 , 10 ]. A recent Astana Declaration recognized those aspects of PHC need to be changed to adapt adequately to current and emerging threats to the healthcare system. This declaration discussed that implementation of a need-based, comprehensive, cost-effective, accessible, efficient and sustainable healthcare system is needed for disadvantaged and rural populations in more local and convenient settings to provide care when and where they want it [ 8 ].

Different innovative approaches have been practiced in different parts of the world to improve access to essential healthcare services in rural communities. Systematically collecting and combining best experiences all over the world is important to suggest effective strategies to improve access to healthcare in developing countries. Accordingly, this systematic review of literature was undertaken to identify key approaches from international experiences to enhance access to PHC services in rural communities. The findings of this systematic literature review can be used by healthcare professionals, researchers and policy makers to improve healthcare service delivery in rural communities.

Methodology

Research question.

What improves access to PHC services in rural communities? We used the PICO (population, issue/intervention, comparison/contrast, and outcome) construct to develop the search question [ 11 ]. The population is rural communities or remote communities in developing countries who have limited access to healthcare services. Moreover, we extended the population to developed countries to capture experiences of both developing and developed countries. The issue/intervention is implementation of different community-based health interventions to access to essential healthcare services. In this systematic review, we focused on PHC health services, mainly essential or basic healthcare services, community or public health services, and health promotion or health education. Primary healthcare is “a health care system that addressed social, economic, and political causes of poor health promotes health though health services at the primary care level enhances health of the community” [ 12 ]. Comparison/contrast is not appropriate for this review. The outcome is improved access to essential healthcare services.

Outcome measures

The outcome of this review is access to PHC services, such as preventive, promotive, curative, rehabilitative, and palliative health services which are affordable, convenient or acceptable, and available to all who need care.

Criteria for considering studies for this review

All published and unpublished qualitative and/or mixed method studies conducted to improve access to PHC services were included. Government and international or national organizations reports were also included. Different organizations whose primary mission is health or promotion of community health were selected. We included articles based on these eligibility criteria: context or scope of studies (access to PHC services), article type (primary studies), and publication language (English). Articles published other than English language, citations with no abstracts and/or full texts, reviews, and duplicate studies were excluded. We included all articles available in different electronic databases regardless of their publication years. We didn’t use time of publication for screening.

Information sources and search strategy

We searched relevant articles from MEDLINE, Scopus, Web of Science, WHO Global Health Library, and Google Scholar to access all forms of evidence. An initial search of MEDLINE was undertaken followed by analysis of the text words contained in the title and abstract, and of the index terms used to describe articles. We used the aforementioned performance indicators of PHC delivery and the PICO as we described above to choose keywords. A second search using all identified keywords and index terms was undertaken across all included databases. Thirdly, references of all identified articles were searched to get additional studies. The full electronic search strategy for MEDLINE, a major database we used for this review is included as a supplementary file (Additional file 1 : Appendix 1).

Study selection and assessment of methodological quality

Search results from different electronic databases were exported to Endnote reference manager version 7 to remove duplication. Two independent reviewers (ZG and BA) screened out records. An initial screening of titles and abstracts was done based on the PICO criteria and language of publication. Secondary screening of full-text papers was done for studies we included at the initial screening phase. We further investigated and assessed records included in the full-text articles against the inclusion and exclusion criteria. We sat together and discussed the eligibility assessment. The interrater agreement was 90%. We resolved disagreements by consensus for points we had different rating. We used the PRISMA flow diagram to summarize the study selection processes.

Methodological quality of the included studies was assessed using mixed methods appraisal tool (MMAT) version 2018 [ 13 ]. As it is clearly indicated in the user guide of the MMAT tool, it is discouraged to calculate an overall score from the ratings of each criterion. Instead, it is advised to provide a more detailed presentation of the ratings of each criterion to better inform quality of the included studies. The rating of each criterion was, therefore, done as per the detail explanations included in the guideline. Almost all the included full text articles fulfilled the criteria and all the included full text articles were found to be better quality.

Data extraction

We independently extracted data from papers included in the review using JBI mixed methods data extraction form. This form is only used for reviews that follow a convergent integrated approach, i.e. integration of qualitative data and qualitative data [ 14 ]. The data extraction form was piloted on randomly selected papers and modified accordingly. One reviewer extracted the data from the included studies and the second reviewer checked the extracted data. Disagreements were resolved by discussion between the two reviewers. Information was extracted from each included study on: list of authors, year of publication, study area, population of interest, study type, methods, focus of the studies, main findings, authors’ conclusion, and limitations of the study.

Synthesis of findings

The included full-text articles were qualitatively analyzed using emergent thematic analysis approach to identify key concepts and coded them into related non-mutually exclusive themes. Themes are strategies mentioned or discussed in the included records to improve access to PHC services. Themes were identified manually by reading the included records again and again. We then synthesized each theme by comparing the discussion and conclusion of the included articles.

Systematic review registration number

The protocol of this review is registered in PROSPERO (the registration number is: CRD42019132592) to avoid unplanned duplication and to enable comparison of reported review methods with what was planned in the protocol. It is available at https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42019132592 .

Schematic of the systematic review and reporting of the search

We used PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) 2009 checklist [ 15 ] for reporting of this systematic review.

Study selection

The search strategy identified 1148 titles and abstracts [914 from PubMed (Table 1 ) and 234 from other sources] as of 10 March 2022. We obtained 900 after we removed duplicated articles. Following assessment by title and abstract, 485 records were excluded because these records did not meet the criteria as mentioned in the method section. Additional 256 records were discarded because the records did not discuss the outcome of interest well and some records were systematic reviews. The full text of the remaining 159 records was examined in more detail. It appeared that 49 studies did not meet the inclusion criteria as described in the method section. One hundred ten records met the inclusion criteria and were included in the systematic review or synthesis (Fig.  1 ).

Study selection flow diagram

Of 900 articles resulting from the search term, 110 (12.2%) met the inclusion criteria. The included full-text articles were published between 1993 and 2021. Ninety-two (83.6%) of the included full-text articles were research articles, 5(4.5%) were technical reports, 3 (2.7%) were perspective, 4 (3.6%) was discussion paper, 3(2.7%) were dissertation or thesis, 2 (1.8%) were commentary, and 1 (0.9) was a book. Thirty-six (33%) and 29 (26%) of the included full-text articles were conducted in Africa and North America, respectively (Fig.  2 ).

Regions where the included full-test articles conducted

Key strategies identified

The analysis of 110 full-text articles resulted in 10 themes. The themes are key strategies to improve access to PHC services in rural communities. The key strategies identified are community health programs or community-directed healthcare interventions, school-based healthcare services, student-led healthcare services, outreach services or mobile clinics, family health program, empanelment, community health funding schemes, telemedicine, promoting the role of traditional medicine, working with non-profit private sectors and non-governmental organizations (NGOs) including faith-based organizations (Table 2 ).

Description of strategies

a. Community health programs or community-directed healthcare interventions

Twenty-four (21.8%) of the full-text articles included in this review discussed that community health programs (CHPs) or community-directed healthcare interventions are best strategies to provide basic health and medical care close to the community to increase access and coverage of essential health services. Community health programs are locally based health promotion, disease prevention, and treatment programs available typically to communities in need and community-directed intervention strategy is an approach in which communities themselves direct the planning and implementation of intervention delivery. Rural communities, especially, in developing countries have no access to healthcare facilities in the near distance and have less chance to receive healthcare from doctors, health officers, nurses or midwives. In response to this critical problems, many countries have been investing heavily in community based primary health care to bring services to rural and remote areas where most of the population lives. Community health programs include construction of health posts or community health centers close to the community and deployment of community health workers (CHWs), such as health extension workers, to reach-out every village, who play a prominent role as the gatekeepers of healthcare in rural communities. Community-directed healthcare intervention is an approach in which communities themselves direct the planning and implementation of healthcare interventions. Community participation remains crucial in the identification of health problems, planning or designing of health interventions and implementation of the interventions, which enhances need-based and demand-driven provision of health services while promoting sustainability and ownership (Additional file 2 : Appendix 2, Table A1).

b. School-based primary healthcare

In this review, 9 of 110 (8.2%) of the included full-text articles pointed out that school-based healthcare services can be effective to improve access to PHC services. School-based health services are health programs that offer health care to children and youth either in a school or on school grounds and usually staffed according to school community needs and resources. School-based health services provide a variety of healthcare services to underserved children, youth and vulnerable populations in a convenient and accessible environment. Access to comprehensive health services via schools leads to improved access to healthcare (Additional file 3 : Appendix 3, Table A2).

c. Student-led healthcare services

In this review, 5 of 110 (4.5%) of the full-text articles discussed that the use of medical and health science students as healthcare service providers can minimize problems related with shortage of health professionals in rural healthcare system and can play appreciable roles to minimize healthcare service access problems in rural communities. Student-led healthcare services are developed through consultation between universities and local health providers and are purposefully designed clinical placements with a focus on clinical educational activities for pre-registration students. Student-led clinics link students, healthcare professionals, community-based organizations, universities, and communities. In this approach, students can gain practical experience in an interdisciplinary setting and through exposure to a community with unique and severe needs (Additional file 4 : Appendix 4, Table A3).

d. Outreach services or mobile clinics

In this systematic literature review, 18 of 110 (16.4%) of the included studies discussed that outreach services or mobile clinics in primary care and rural hospital settings can improve access to PHC services in rural communities. Mobile outreach service is defined as healthcare services provided by a mobile team of trained providers, from a higher-level health facility to a lower-level health facilities or locally available community facilities that are not used for clinical services, such as schools, health posts, or other community structures. Outreach services improve access to specialists and hospital-based services, strengthen connections between specialists and PHC providers, and give the benefits of consultations in primary care settings. Specialist outreach services have the potential to overcome access barriers faced by disadvantaged rural and remote communities. Furthermore, a community-based mobile clinics can be effective in uncovering illness and in directing patients to a healthcare home (Additional file 5 : Appendix 5, Table A4).

e. Family health program

Four (3.6%) of the included full-text articles discussed that family health program (FHP) is highly cost-effective tool for improving access to healthcare services for deprived areas (such as rural communities). Family health program means the program is a program designed to provide primary care as well as the prevention and early treatment of communicable and non-communicable diseases in defined populations by deploying interdisciplinary healthcare teams include physicians, nurses, nurse assistants, and full-time community health agents. It has evolved into a robust approach to providing primary care for defined populations by deploying interdisciplinary healthcare teams. The nucleus of each team includes a physician, a nurse, a nurse assistant, and full-time community health agents. This approach is effective on improving access to healthcare and eliminating health disparities (Additional file 6 : Appendix 6, Table A5).

f. Empanelment

This systematic review of literature identified that empanelment (also known as rostering) is a best strategy to proactively provide coordinated primary healthcare towards achieving universal health coverage. Empanelment is a continuous, iterative set of processes that identify and assign populations to facilities, care teams, or primary care providers who have a responsibility to know their assigned population. It enables health systems to improve health outcomes and to reduce costs. Empanelment establishes a point of care for individuals and simultaneously holds primary healthcare providers and care teams accountable for actively managing care for a specific group of individuals (Additional file 7 : Appendix 7, Table A6).

g. Community health funding schemes

In this systematic review of literature, 11 (10%) of the included articles discussed that community health funding schemes such as community-based health insurance (CBHI) increases access to healthcare services in low-income rural communities. Community-based health insurance schemes are usually voluntary and characterized by community members pooling funds to offset the cost of healthcare. Moreover, this approach is effective to mobilize domestic resources for health at low income levels. For low-income countries, community health financing has modest ability to increase the total amount of funds for healthcare. Properly structured community health financing system can significantly improve efficiency, reduce the cost of healthcare, improve quality and health outcomes, and pool risks. Community-financing schemes could improve preventive services and reduce the incidence of diseases. It could also improve people’s access to healthcare and the quality of services, thus improving their health status. Community health financing could also improve risk pooling and reduce health-induced impoverishment. Community health insurance has potential positive impacts on health and social security (Additional file 8 : Appendix 8, Table A7).

h. Telemedicine

In this review, 13 of 110 (11.8%) articles discussed that telemedicine is one of the solutions for rural subspecialty healthcare delivery. Telemedicine can be defined as the use of technology (computers, video, phone, messaging) by a medical professional to diagnose and treat patients in a remote location. The provision of subspecialty services using telemedicine to a remote and medically underserved population provides improved access to subspecialty care. Telemedicine brings sustainable healthcare to rural populations. Use of information and communication technologies in support of health and health-related fields, including healthcare services, health surveillance, health education, and health research has the potential to greatly improve health service efficiency, expand or scale up treatment delivery to thousands of patients in the rural populations (Additional file 9 : Appendix 9, Table A8).

i. Promoting the role of traditional medicine

Seven (6.4%) of the included articles showed that incorporating traditional healers into public health system addresses healthcare needs of people with limited access to allopathic medicine. Traditional medicine is the sum total of the knowledge, skill, and practices based on the theories, beliefs, and experiences indigenous to different cultures, whether explicable or not, used in the maintenance of health as well as in the prevention, diagnosis, improvement or treatment of physical and mental illness. Knowledge about traditional medicine has a catalyzing effect in meeting health sector development objectives. Integrating traditional medicine into national health systems in combination with national policy and regulation for products, practices and providers can enhance access to PHC services in remote populations (Additional file 10 : Appendix 10, Table A9).

j. Working with non-profit private sectors and non-governmental organizations

In this systematic review, 15 of 110 (13.6%) of the included articles revealed that working with non-profit private sectors and NGOs strengthens the healthcare system. Involving the non-profit private sectors, faith-based organizations (FBOs), and NGOs for health system strengthening eventually contributes to create a healthcare system reflecting an increased efficiency, more equity and good governance in health. International and local NGOs have endeavored to fill the gaps in access to healthcare services, research and advocacy. Non-profit private sectors and NGOs have a key role in improving health in low- and middle-income countries. With networks that reach even the most remote communities, many FBOs are well positioned to promote demand and access for healthcare services. Partnership among FBOs is critical in increasing access to healthcare services, and ensuring sustainability by influencing behaviors at the community, family and individual level. Faith-based organizations play an integral role in the healthcare system by increasing health seeking behaviors and delivering supportive services that address common access and cultural barriers (Additional file 11 : Appendix 11, Table A10).

This systematic literature review found that community health programs or community-directed healthcare interventions, school-based healthcare services, student-led healthcare services, outreach services or mobile clinics, family health program, empanelment, community health funding schemes, telehealth, integrative medicine, and working with non-profit private sectors and NGOs are key strategies to improve access to PHC services in rural communities. The identified strategies address the four major pillars of primary healthcare (i.e., community participation, inter-sectoral coordination, appropriate technology, and support mechanism made available) [ 126 ]. Moreover, the identified strategies are effective to improve access to healthcare services to rural communities. Moreover, the identified strategies are effective to solve shortage of manpower and to build knowledge and skill of the local health workforces in rural healthcare system. The ability of a healthcare system to meet health needs of the population depends largely on the knowledge, skills, motivation and deployment of the people responsible for organizing and delivering health services. The results of this review can strengthen the health information system, which are core elements of the healthcare system that ensure community engagement through dissemination and use of timely and reliable health information to rural populations. This review also suggests strategies to narrow down the health disparities among rural populations, which is wide in most Least and Middle Income Countries (LMICs). Healthcare services are usually disproportionately concentrated in major urban areas. As a result, rural communities face growing health disparities, largely attributed to weak policies, inefficiencies, poor leadership, and governance in healthcare system.

This review identified that community health programs or community-directed healthcare interventions address health disparities by ensuring equitable access to health resources in communities where health equity is limited by socioeconomic and geographical factors. Community health programs include identifying and prioritizing public health problems in a specific geographic area; designing and implementing public health interventions (such as establishing community health centers, mobile clinics, and outreach programs); providing services (such as health education, screenings, social support, and counseling), and deploying community health workers to promote healthy behaviors; advocating for improved care for populations at risk; and working with stakeholders to address community healthcare needs [ 16 , 17 , 18 , 127 , 128 , 129 , 130 ]. The community-oriented PHC model which is socially responsive medicine makes a healthcare system more rational, accountable, appropriate, and socially relevant to the public. Consequently, this model serves as a paradigm for reforming healthcare systems. Community-directed interventions can be considered as a realistic means to increase accessibility of interventions at community-level in rural areas [ 32 , 33 , 34 , 35 , 36 , 37 , 38 ]. This approach is best in situations where there are cultural barriers to implement interventions because this strategy is effective to develop ownership in the community. In-service and on-the-job training for community health workers, close supervision and government support, and program evaluation is very important to strengthen the community health program [ 131 , 132 , 133 ].

This review identified that school-based PHC services are effective strategies to improve access to PHC services. School-based health services provide a variety of healthcare services to children, youth and vulnerable populations in a convenient and accessible environment which indirectly improve leadership and governance. Science teachers and home room teachers play important roles to implement this strategy. It impacts on delivering preventive care such as immunizations, managing chronic illnesses and providing reproductive health services for adolescents. Comprehensive health services via schools improve access to healthcare information [ 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 ]. Access to school around the world increased drastically in the last century [ 134 ]. This high schooling rate is a good opportunity to provide healthcare services to school learners in accessible places and to disseminate health messages to families. Prior researches suggest that school-based healthcare services increase access to healthcare by increasing utilization of primary care, prevention services, and health maintenance visits [ 135 , 136 ]. Including science teachers, home room teachers, school principals, students, communities, community health workers, and other interested parties in the school-based healthcare system as main actors or promoters must be considered to sustain the impact. Health and education sectors should work in collaboration with the above-mentioned actors to plan, implement and monitor the progress. School-based healthcare services are preferable in situations when there is high schooling rate and limited access to healthcare institutions. This strategy is also an alternative way in areas where the health seeking behavior of the community is low.

The use of medical and health science students in rural healthcare system was identified as a key strategy to minimize health inequalities in rural communities due to shortages in health workforce and distribution of healthcare resources [ 49 , 50 , 51 , 52 , 53 ]. Student-led health intervention is an alternative approach to provide essential healthcare services to the community where there is shortage of healthcare workers [ 137 , 138 ]. Students will have opportunities to learn professional skills and competencies while they are providing healthcare services to the community. Moreover, benefits for student learning include increased communication, collaboration, and leadership skills [ 53 , 139 ]. Student-led health intervention also enables increased access to services, more time for assessments and treatments, increased depth of health teaching, holistic and integrated healthcare, and free health supports [ 140 , 141 , 142 , 143 ]. However, the use of medical and health science students in the rural healthcare system may have ethical and competency issues. Supporting strategies such as close supervision, preparing clear protocols, and including senior experts in the team should be considered.

This systematic review of literature found that outreach services or mobile clinics can improve access to PHC service delivery in rural populations [ 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 ]. In developing countries, the highest proportion of people lives in rural areas where doctor services are not available. Rural communities travel to major cities to get specialist services. This reflects a desire for closer integration between primary and secondary care. Specialist outreach services or mobile clinics have become one of the effective solution to solve health disparities, to improve access to healthcare services, and to build capacity of local healthcare workforces. This strategy is preferable in situations when there are high loads in tertiary or referral level hospitals and when there is high patient leakage in the referral system [ 63 , 64 , 65 , 66 , 67 , 68 , 69 ]. However, the implementation may not be easy. It needs well established healthcare system and budget. Moreover, the efficiency of care may be lower compared with hospital-based cares and the effect on patients’ health outcomes might be small [ 56 , 57 , 61 ] . Irregular specialist visits in rural areas may not have real impacts unless the services are sustainable with a strong commitment at national and local levels. Outreach activities should be included in health policies with strong leadership, healthcare financing, and private initiatives must be encouraged to maintain the activities over time.

This review revealed that FHP is highly effective tool for improving health for rural communities. The FHP has provided a new, more robust model of primary healthcare services designed to provide accessible, first contact, comprehensive, and whole person care that is coordinated with other healthcare services. It has positive results to improved availability, access to, and use of health services, and improved health indicators, such as reduced infant mortality, improved detection of cases of neglected diseases, and reduced health disparities [ 73 , 144 , 145 , 146 ]. The FHP deploys interdisciplinary healthcare teams. The team includes a physician, a nurse, a nurse assistant, and full-time community health agents. Family health teams are organized geographically. The teams are responsible for delivering public health interventions [ 72 , 74 ]. Family health program is an alternative strategy in rural healthcare system in situations when there are inequities in access to care; when there is high hospitalization rate; when there is low health seeking behavior in the community; and when there is poor case detecting and reporting system. Despite these remarkable achievements, the FHP has some challenges include difficulties in the recruitment and retention of doctors trained appropriately to deliver primary healthcare, large variations in quality of local care, patchy integration of primary care services with existing secondary and tertiary care, and slow adoption of FHP in large population [ 147 ].

In this review, empanelment has been identified as a best strategy to deliver coordinated primary healthcare towards achieving universal health coverage [ 76 , 77 , 78 , 79 ]. The goal of empanelment is provide people-centered healthcare services based on their needs to ensure that every established patient receives optimal care, whether he/she regularly visits healthcare centers. Major activities in this approach include assignment of all patients to a healthcare provider panel; update panel assignments on a regular basis; and use panel data to educate, and track patients [ 79 ]. Empanelment enables healthcare systems to improve patient experiences, reduce costs, and improve health outcomes. Empanelment is an effective strategy to deliver four key functions: first-contact accessibility, continuity, comprehensiveness, and coordination [ 148 ]. Effective empanelment requires responsibility for the health of a target population, including providing healthcare services based on their health status, which is an important step in moving towards people-centered integrated healthcare [ 79 ].

This review identified that community health funding schemes such as community-based health insurance (CBHI) increases access to healthcare in low-income rural communities. Moreover, this approach is effective to mobilize domestic resources for health at low income levels [ 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 ]. Community-based health insurance is an emerging strategy to provide financial protection against the cost of illness. It is an effective strategy to improve access to quality health services for low-income rural households [ 149 ]. Existence of social capital in the community is a determinant factor for the effectiveness of CBHI as social capital has a positive effect on the community's demand for insurance [ 150 , 151 ]. Moreover, solidarity and trust between the members are the key principles for the good functioning of a CBHI. Solidarity and trust stir-up members who are susceptible to risk to put together their resources for common use [ 149 , 152 , 153 ]. Affordability of premiums or contributions, technical arrangements made by the scheme management, timing of collecting the contributions, trust in the integrity and competence of the managers of the CBHI, The quality of care offered through the CBHI, accessible across different population groups are some of the determinant factors to be considered to increase people’s decision to join the CBHI schemes [ 154 , 155 ].

In this review, telemedicine has been identified as one of the many possible solutions for rural subspecialty healthcare delivery. Telemedicine is a vital technological tool to increase healthcare access, improve care delivery systems, engage in culturally competent outreach, health workforce development, and health information system [ 91 , 92 , 93 , 94 , 95 , 96 , 97 , 98 , 99 , 100 ]. Telemedicine can be a great alternative to the traditional healthcare system in situations like diagnoses of common medical problems; inquiries about various medical issues for home treatments; post-treatment check-ins or follow-up for chronic care; holidays, weekends, late night or any other situation when regular medical care is not possible; patient inability to leave the house; patients who lack regular access to relevant medical expertise in their geographic area ; and etc. However, technological issues are challenges when dealing with telemedicine, especially in developing countries. General problems of Internet connectivity and access to infrastructure can minimize benefits of this strategy. Costs associated with technology can also be a barrier. Furthermore, health technology requires human capacity to use it. Therefore, strengthening the information communication technologies (ICT) and human capacity building on ICT are important to address the health needs of the rural communities.

This systematic review of literature identified that promoting the role of TM solves problems of access to allopathic medicine. Integration of TM in health system will result in increased coverage and access to healthcare services. The role of complementary and alternative medicine for health is undisputed particularly in light of its role in health promotion and well-being. It also supports local health workforces [ 104 , 105 , 106 , 107 , 108 , 109 ]. Incorporating traditional healers into the public health system addresses healthcare needs [ 156 , 157 ]. However, integrating TM to the public healthcare system is challenging. It is a general belief that TM defies scientific procedures in terms of objectivity, measurement, codification and classification [ 157 ]. If integrated, who provides training to medical doctors on the ontology, epistemology and the efficacies of TM in modern medicine [ 157 ]. Due to these, some scholars suggest that both TM and modern medicine be allowed to operate and develop independent of one another [ 158 , 159 ]. Another fundamental challenge to TM is the widespread reported cases of fake healers and healings [ 157 ]. Generally, this strategy is more of feasible in areas where formal trainings on integrative medicine are available. Even though the integration is challenging, the health sector can use traditional healers as health educators or health promoters by providing training and continuous support. It can be also possible to use traditional healers as facilitators in the community-directed approaches. In general TM can be used in the primary healthcare system where no access to allopathic medicine and when conventional medicine is ineffective in treatment of disease [ 160 ].

Working with non-profit private sectors and NGOs has been identified as effective strategies to strengthen the healthcare system in developing countries [ 111 , 112 , 113 , 114 , 115 , 116 , 117 , 118 ]. Since governments in developing countries are challenged to meet the health needs of their populations because of financial constraints, limited human resources, and weak health infrastructure; the private sector (especially the non-profit private sectors) and non-governmental organizations can help expand access to healthcare services through its resources, expertise, and infrastructure. However, the presence of an NGO in the operation, may contribute to unrealistic expectations of health services, affecting perceptions of the latter negatively [ 113 ]. Moreover, reports have it that besides other issues in many instances NGOs allocated funds only to disease specific projects (vertical programming) rather than to broad based investments (horizontal programming) [ 161 ]. There are also concerns that donor expenditures in developing countries are not only unsustainable but may be considered as inadequate considering the enormous healthcare burden [ 161 , 162 , 163 , 164 ]. To avoid unrealistic expectations and dissatisfaction, and to increase and sustain the population’s trust in the organization, NGOs should operate in a manner that is as integrated as possible within the existing structure and should work close to the population it serves, with services anchored in the community. Moreover, faith-based organizations contribute in health such as disease prevention, health education or promotion, and community health development beyond psychological and spiritual care [ 119 , 120 , 121 , 122 , 123 , 124 ]. Religious organizations can reach all segments of rural populations. Therefore, integrating PHC services, especially health education and promotion, diseases prevention and community health development with religious organizations intensifies delivery of healthcare services. Working with FBOs is a best way in situations where cultural and faith-based barriers are common and in areas, where access problems are often related to lack of providers. However, religious organizations need intensive training on health promotion and health system to enable them to respond to local contexts within the framework of national policies. Moreover, there should be strong partnership with government agenesis to sustain the effort [ 165 , 166 , 167 , 168 ].

Contribution of this review

Various studies reported one or more strategies to improve access to primary healthcare services. However, the strategies reported by individual studies are not compiled together and there is lack of pooled evidence on effective strategies to improve access to healthcare system. This systematic literature review was, therefore, conducted to compile effective strategies to improve access to healthcare services in rural communities. The review suggests key strategies to improve access to PHC services in rural communities. These suggested strategies are implementable in countries that suffer from shortage of health workers and healthcare financing because all the strategies used locally available opportunities. The local healthcare system needs, therefore, scan the available opportunities in the locality for implementing the suggested strategies and needs to integrate the strategies in the healthcare system to sustain the impacts. Healthcare providers, researchers and policy makers could use the results of this systematic literature review to increase access to healthcare services in hard-to-reach areas. As the strategies are compiled from experiences of different countries (developed and least developed countries), there might be contextual differences like socio-economic, cultural, institutional, and geographical challenges to adopt the identified strategies. Moreover, some of the experiences only come from one or two countries. Therefore, strategy developers and implementers need to consider these contextual challenges or variation during adopting and implementing different strategies.

Strengths and limitations of the study

As a strength, this systematic review explores international (both developed and developing countries) best experiences on primary healthcare service delivery and identified ten key approaches to improve access to PHC services in rural communities. We also searched relevant published or unpublished articles, dissertations or theses, discussion papers, and perspectives from a wide range of sources, such as MEDLINE, Scopus, Web of Science, WHO Global Health Library, and Google Scholar.

As a limitation, we entirely relied on electronic databases to search relevant articles. We didn’t include locally available printed out records. We also applied limits for language. We excluded articles published other than English language. We believed we could get more relevant articles if we had access to records available in prints and if we include articles published other than English language. Furthermore, since the strategies are compiled from experiences of different countries (developed and least developed countries), there might be contextual differences like socio-economic, cultural, institutional and geographical challenges to adopt the identified strategies. There was also limited evidence for some articles, especially reports to rate their methodological quality. Readers should also note that our review might missed some important work in improving access to PHC services and the identified strategies are not the only strategies to improve access to PHC services. There might be other effective strategies which are not included in this review. In addition generalizability might be affected since some of the experiences only come from one or two countries. Moreover, this review focuses on access not quality of care delivered.

This review identified key strategies from international experiences to improve access to PHC services in rural communities. These strategies are effective to improve access to healthcare services in rural or remote communities. They can also play roles in achieving UHC and reducing disparities in health outcomes and increase access to rural communities to get healthcare when and where they want. Therefore, incorporating these key strategies suggested by this review in to the healthcare system is useful to enhance PHC services and to minimize impacts of health disparity in rural communities. However, the identified strategies may not be easy to implement. Increasing number and capacity of human resource for health; strengthening the healthcare financing system; improving medicine and supplies; working in different partners and communities; establishing monitoring and evaluation system; strong and committed leadership; and encouraging private initiatives must be considered to implement and maintain these strategies over time. Moreover, policy makers, program planners and implementers who want to utilize findings of this review should be aware that these are not the only effective strategies to improve access to primary healthcare services.

Availability of data and materials

All the extracted data are included in the manuscript.

Abbreviations

Community-based health insurance

Faith-based organizations

Family health program

Information communication technologies

Mixed methods appraisal tool

Non-governmental organizations

• Primary healthcare

Primary Health Care Performance Initiative

Population, phenomena of interest and context)

Traditional medicine

Universal health coverage

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Acknowledgements

The author would like to thank IPHC- E for funding this review.

This review was funded by International Institute for Primary Health Care- Ethiopia (IPHC- E).

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Supplementary Information

Additional file 1: .

Searchstrategy. MEDLINE (PubMed).

Additional file 2: Appendix 2: Table A1.

Description of full-text articles which discussed community health programs or community-directed interventions as a strategy to improve PHC service delivery in ruralcommunities.

Additional file 3:

Appendix 3: Table A2. Description of full-text articles which discussed school-based healthcareservices as a strategy to improve PHCservice delivery in rural communities.

Additional file 4:

Appendix 4: Table A3. Description of full-text articles which discussed student-led healthcareservices as a strategy to improve PHC service delivery in ruralcommunities.

Additional file 5: Appendix 5: Table A4

. Descriptionof full-text articles which discussed outreach services or mobile clinics as astrategy to improve PHC service delivery in ruralcommunities.

Additional file 6:

  Appendix 6: Table A5. Description of full-text articles which discussed family health program as astrategy to improve PHC service delivery in rural,communities.

Additional file 7:

  Appendix 7: Table A6. Description of full-text articles whichdiscussed empanelment as a strategy to improve PHC service delivery in ruralcommunities.

Additional file 8:

  Appendix 9: Table A8. Description of full-text articles which discussed telemedicine or mobile healthas a strategy to improve PHC service delivery in ruralcommunities.

Additional file 9:

  Appendix 8: Table A7. Description of full-text articles which discussed community health funding schemes as a strategy to improve PHC service delivery in ruralcommunities.

Additional file 10:

  Appendix 10: Table A9. Description of full-text articles which discussed promoting the role of workingwith traditional healers as a strategy toimprove PHC service delivery in rural communities.

Additional file 11:

  Appendix 11: Table A10. Description of full-text articles which discussed working with non-profitprivate sectors and non-governmental organizations as a strategy to improve PHC service delivery in rural communities.

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Gizaw, Z., Astale, T. & Kassie, G.M. What improves access to primary healthcare services in rural communities? A systematic review. BMC Prim. Care 23 , 313 (2022). https://doi.org/10.1186/s12875-022-01919-0

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Consolidated guidance for behavioral intervention pilot and feasibility studies

• Christopher D. Pfledderer   ORCID: orcid.org/0000-0001-7503-8554 1 , 2 ,
• Lauren von Klinggraeff 3 ,
• Sarah Burkart 3 ,
• Alexsandra da Silva Bandeira 3 ,
• David R. Lubans 4 ,
• Russell Jago 5 ,
• Anthony D. Okely 6 ,
• Esther M. F. van Sluijs 7 ,
• John P. A. Ioannidis 11 , 12 , 8 , 9 , 10 ,
• James F. Thrasher 3 ,
• Xiaoming Li 3 &
• Michael W. Beets 3  

Pilot and Feasibility Studies volume  10 , Article number:  57 ( 2024 ) Cite this article

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In the behavioral sciences, conducting pilot and/or feasibility studies (PFS) is a key step that provides essential information used to inform the design, conduct, and implementation of a larger-scale trial. There are more than 160 published guidelines, reporting checklists, frameworks, and recommendations related to PFS. All of these publications offer some form of guidance on PFS, but many focus on one or a few topics. This makes it difficult for researchers wanting to gain a broader understanding of all the relevant and important aspects of PFS and requires them to seek out multiple sources of information, which increases the risk of missing key considerations to incorporate into their PFS. The purpose of this study was to develop a consolidated set of considerations for the design, conduct, implementation, and reporting of PFS for interventions conducted in the behavioral sciences.

To develop this consolidation, we undertook a review of the published guidance on PFS in combination with expert consensus (via a Delphi study) from the authors who wrote such guidance to inform the identified considerations. A total of 161 PFS-related guidelines, checklists, frameworks, and recommendations were identified via a review of recently published behavioral intervention PFS and backward/forward citation tracking of a well-known PFS literature (e.g., CONSORT Ext. for PFS). Authors of all 161 PFS publications were invited to complete a three-round Delphi survey, which was used to guide the creation of a consolidated list of considerations to guide the design, conduct, and reporting of PFS conducted by researchers in the behavioral sciences.

A total of 496 authors were invited to take part in the three-round Delphi survey (round 1, N  = 46; round 2, N  = 24; round 3, N  = 22). A set of twenty considerations, broadly categorized into six themes (intervention design, study design, conduct of trial, implementation of intervention, statistical analysis, and reporting) were generated from a review of the 161 PFS-related publications as well as a synthesis of feedback from the three-round Delphi process. These 20 considerations are presented alongside a supporting narrative for each consideration as well as a crosswalk of all 161 publications aligned with each consideration for further reading.

We leveraged expert opinion from researchers who have published PFS-related guidelines, checklists, frameworks, and recommendations on a wide range of topics and distilled this knowledge into a valuable and universal resource for researchers conducting PFS. Researchers may use these considerations alongside the previously published literature to guide decisions about all aspects of PFS, with the hope of creating and disseminating interventions with broad public health impact.

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Key messages regarding feasibility

• There are more than 160 published guidelines, reporting checklists, frameworks, and recommendations related to PFS. All these publications offer some form of guidance on PFS, but many focus on one or a few topics, making it difficult for researchers wanting to gain a broader understanding of all the relevant and important aspects of PFS and requires them to seek out multiple sources of information, which increases the risk of missing key considerations to incorporate into their PFS.

• We present a set of consolidated considerations for behavioral intervention pilot and/or feasibility studies based on a review of the literature and a Delphi study with the authors who wrote this literature.

• We believe this consolidated set of considerations can be a “go-to” resource for any behavioral interventionist wanting to design, conduct, and report on their pilot and/or feasibility study.

In the behavioral sciences, conducting pilot and/or feasibility studies (PFS) is a key step that occurs early in the translational science continuum. PFS provide essential information to inform the design, conduct, and implementation of larger-scale trials, although not all studies follow the traditional roadmap to scale-up [ 1 ]. PFS are designed to answer questions surrounding uncertainty (feasibility) and potential impact (preliminary efficacy) and to inform gaps in knowledge about the various aspects of the intervention or conduct of the study. In turn, this information is used to make decisions regarding scale-up and future plans for a larger-scale trial.

There are more than 160 published guidelines, checklists, frameworks, and recommendations related to the design, conduct, and reporting of PFS. These publications offer some form of guidance on PFS, but many focus on a specific aspect of design, conduct, and reporting considerations. This makes it difficult for researchers who want to gain a broader understanding of all the relevant and important aspects of PFS and forces them to seek out multiple sources of information, which increases the risk of missing key considerations to incorporate into their PFS. Because of this, we believe a consolidated list of considerations, drawing on the breadth and depth of knowledge that has already been published on the topic, would have high utility for researchers and assist them in understanding important considerations and nuances when conducting a PFS.

Throughout this paper, we refer to PFS as early-stage studies designed to inform larger-scale, well-powered trials. We recognize that there are numerous labels for such studies (e.g., “proof-of-concept”, “evidentiary”, “vanguard”). We also realize that the terms “pilot” and “feasibility” evoke different meanings [ 2 , 3 ] and are used interchangeably and, in some instances, simultaneously. We address this issue in this consolidation of considerations. We also recognize that not all PFS will include or need to consider all the identified considerations. In many instances, however, a single PFS is designed to cover all of the data needed to inform a larger-scale trial [ 4 ]. This includes everything from estimating recruitment/retention rates, participant satisfaction and engagement, fidelity, and a host of other feasibility indicators, as well as providing some preliminary indications of change in one or more outcomes of interest. Researchers often deliberately design a PFS to collect information across these multiple dimensions, though their decision making is often largely driven by such issues as available resources and abbreviated timelines.

The purpose of this study was to develop a consolidated set of considerations for the design, conduct, implementation, and reporting of PFS for interventions in the fields of behavioral sciences. The considerations presented herein were developed through any extensive review of the literature and a Delphi study of experts who wrote the existing literature on PFS. The consolidated set of considerations was developed for universal application across interventions in the behavioral sciences and across the study designs one may choose. We expect this consolidation will serve as a valuable resource for all behavioral science interventionists who design and conduct PFS, regardless of the intervention mechanism, target population, or study design.

To ensure rigor and methodological quality throughout the consolidation of previously published guidelines, checklists, frameworks, and recommendations, we relied on guidance from Moher et al., [ 5 , 6 ] which details the main steps in the development of evidence-based consensus in health fields. These steps included developing a strong rationale for the consolidation, necessary preparatory work conducted by the study team, consensus activities, and development of the final consolidation. These steps are detailed below. When relevant, we also drew on similar consensus studies conducted in the behavioral sciences [ 2 , 3 , 7 , 8 ].

Review of previously published guidelines, checklists, frameworks, and recommendations for PFS

A scoping bibliometric review of published PFS-related guidelines, checklists, frameworks, and recommendations was conducted prior to developing the Delphi survey, which has been reported elsewhere [ 9 ]. Briefly, we identified 4143 PFS from which we then identified 90 guidelines, checklists, frameworks, and recommendations cited in that literature. We then continued searching for relevant literature via backward citation tracking of known publications, including the CONSORT Extension for Pilot and Feasibility Studies [ 7 ], Medical Research Council guidance [ 10 ], and publications such as Bowen et al. [ 11 ] and Pearson et al. [ 12 ] A total of 161 publications were identified that encompassed nine thematic domains: adaptations , definitions of pilot and feasibility studies , design and interpretation , feasibility , implementation , intervention development , progression criteria , sample size , and scale-up . The 161 publications guided our inclusion of the sample of respondents for the Delphi survey, which is detailed in the next section. It is worth noting that after this review, we identified an additional relevant publication published after the completion of the study, which is included in our final sample (bringing the total number of studies to 162) but was not used to inform the Delphi study.

Participant selection and recruitment for the Delphi survey

Lead, second, corresponding, and senior authors of the 161 published guidelines, checklists, frameworks, and recommendations for PFS were invited via email to complete a three-round Delphi study. Contact information was retrieved from published article meta-data and when not found in the published articles, emails were retrieved from another publicly available source, such as faculty pages or university websites. This resulted in 496 potential participants, who were sent an individualized invitation email via Qualtrics for round 1 of the Delphi study. For round 2, only participants who completed round 1 were invited to take part in the survey. We then sent the round 3 survey back to the original pool of 496 potential participants, regardless of whether they completed round 1. This process is summarized in Fig.  1 and took place between May 2022 and January 2023. Ethical approval was granted by the University of South Carolina’s Institutional Review Board (IRB # Pro00120890) prior to the start of the study.

Participant flow through each round of the Delphi survey process

Delphi survey

Each round of the Delphi survey process was guided by established protocols [ 13 , 14 ] and is detailed below.

Round 1—Delphi survey

In round 1 of the Delphi process, participants were asked to provide the most important considerations regarding the design, conduct, analysis, or reporting of behavioral pilot and/or feasibility intervention studies in separate free-text fields via Qualtrics. Before beginning the survey, participants were provided with operational definitions of both “behavioral interventions” and “preliminary studies” for context. No other prompts were provided. In round 1 of the Delphi study, we referred to PFS as “preliminary” studies, but after receiving comments about the use of this term, this was changed to “pilot and/or feasibility” studies in round 2. Survey distribution for round 1 took place in May and June 2022.

Preparation for round 2

Participants’ responses from round 1 were exported from Qualtrics to a.csv file in Microsoft Excel, collated into individual Microsoft Word documents for each participant, converted to PDFs, and imported into NVivo for thematic coding. Prior to coding responses in NVivo, we simplified and revised our original nine thematic domains from the scoping bibliometric review into six overarching themes: intervention design , study design , conduct of trial , implementation of intervention , statistical analysis , and reporting . This revision was conducted after an initial review of responses from round 1 of the Delphi survey in an effort to simplify themes and to allow for maximum parsimony across expert perspectives. Specifically, we identified overlap in several of the original nine themes and made a decision to include them as subthemes in the revision to six overarching themes. The titles of the original nine thematic domains were largely retained and can be found embedded as subthemes in the six revised overarching themes. A two-step thematic coding process followed. First, individual participant responses were coded into a corresponding theme based on the content of their response. This was completed by two members of the research team (CDP and MWB). Disagreements were brought to the larger research team (LV, SB, and AB) during weekly meetings and were resolved at that time. Once participant responses were coded into one of the six overarching themes, our research team coded responses into one of 20 subthemes based on qualitative analysis of participants’ responses by theme. These 20 subthemes served as the coding framework for the second step of the thematic coding process, and responses were coded as such by two members of the research team (CDP and MWB).

Round 2—Delphi survey

In round 2 of the Delphi study, participants were re-oriented to the study with a brief narrative and were presented with the six overarching themes and 20 subthemes generated via qualitative analysis of the results from round 1. To give participants context, we provided select, representative quotes for each subtheme from round 1 of the survey. After being presented with the theme, subtheme, and select quotes, participants were asked to provide a recommendation for each subtheme for inclusion in a consolidated framework for behavioral intervention PFS. Participants were also given the chance to indicate if they felt a subtheme should not be included in a consolidated framework. The survey was organized such that each theme (along with the corresponding subthemes) was presented as a randomized block, meaning individual participants were presented with a unique order of themes and asked to provide their considerations. Block randomization of themes was performed to prevent the possibility of homogenous burnout across participants as they reached the last theme of the survey. The last question of the survey was a free-text field in which participants could indicate if there were any additional considerations that were not mentioned in the survey that should be added to a consolidated framework for pilot and/or feasibility behavioral intervention studies. Survey distribution for round 2 took place in September and October 2022.

Preparation for round 3

Participant responses from round 2 were exported from Qualtrics to a.csv file in Microsoft Excel and collated into individual Microsoft Word documents for each of the 20 subthemes. A collection of considerations for each subtheme was written based on participant responses from rounds 1 and 2 and from information provided throughout the previously identified 161 pilot and/or feasibility-related guidelines, checklists, frameworks, and recommendations. Weekly research group meetings were used to further refine the considerations.

Round 3—Delphi survey

In the final round of the Delphi study, participants were first asked to provide basic demographic information including age, sex, race/ethnicity, and the year in which they received their terminal degree. Demographic information was not collected from participants in round 1 or 2 of the Delphi survey to limit participant burden in the initial rounds of the survey. We then provided participants with an outline of the six themes and 20 subthemes that emerged from rounds 1 and 2 of the study, a description of the final recommendation for the study, and instructions for the final survey. For each of the 20 subthemes, participants were given an operational definition of the subtheme and a list of considerations, which were generated based on the comments from rounds 1 and 2. They were then asked to rate their level of agreement with the considerations (0–10 Likert scale from Strongly Disagree to Strongly Agree). An optional free-text field was provided for additional information about what we should add to/change about the considerations. Participants were presented with each subtheme in block-randomized order just as in round 2. Survey distribution for round 3 took place in December 2022 and January 2023.

Final consolidation of considerations

The final set of considerations was written in a similar manner to round 2. Responses were collated into separate working documents for each of the 20 subthemes, which also included the list of previously written considerations drafted for round 2. The previously written considerations were altered based on participant feedback from round 3 and from further supporting information from the 161 pilot and/or feasibility-related guidelines, checklists, frameworks, and recommendations. Primary changes to the considerations were made by two members of the research team (CDP and MWB) and further refined by members of our larger research team (LV, SB, and AB).

Analysis of quantitative data

There were two forms of quantitative data gathered from participants during round 3 of the Delphi survey process. The first was demographic information, which was summarized descriptively as means, standard deviations, and ranges where appropriate. The second were the participant’s Likert-scale ratings of each set of considerations for each of the 20 subthemes. These data were summarized visually with boxplots and descriptively with means, standard deviations, medians, ranges, and interquartile ranges. All quantitative analysis was performed in STATA v17.0 statistical software package (College Station, TX, USA).

Participant characteristics and survey completion

A total of 46 of the 496 (9.3%) invited authors representing 51 of the 161 (31.7%) identified publications completed round 1 of the Delphi study. In round 1, where respondents were asked to provide up to 20 considerations regarding the design, conduct, analysis, or reporting of behavioral pilot and/or feasibility intervention studies, participants gave a mean of 8 ± 4 (range = 1–20, median = 7, IQR = 5–10) considerations. Of the 46 participants who completed round 1, 24 (52.2%) completed round 2. A total of 50 (10.1%) of the original pool of 496 participants representing 60 (37.3%) publications completed round 3. For the 161 publications that were represented by authors in the Delphi study, the median year of publication was 2015 (range = 1998–2022, IQR = 2013–2018). Comparatively, across all possible 161 identified publications, the median year of publication was 2013 (range = 1989–2022, IQR = 2009–2017). A visual summary of participant flow through each of the three rounds of the Delphi survey process is provided in Fig.  1 . Demographic information for participants who completed round 3 is presented in Table  1 .

Likert ratings of the considerations

Likert scale ratings (0–10 scale) of each of the considerations for the 20 subthemes were provided by 50 out of 50 (100%) participants during round 3 of the Delphi survey. These are summarized in Table  2 . Average ratings for considerations across all 20 subthemes ranged from 7.6 to 8.8, with medians ranging from 8 to 10.

Consolidated considerations for PFS

For each subtheme, we provide an operational definition of the subtheme, a consolidated list of considerations based on the review of pilot and/or feasibility literature and the three-round Delphi study, and a narrative summary of the subtheme. We also provide a crosswalk of 161 guidelines, checklists, frameworks, and recommendations, mapped on to the subthemes identified and an additional publication that was published after the Delphi process, but was relevant to include in the list [ 15 ]. The crosswalk is found in Additional file 1 and can be used to identify supporting literature for each of the subthemes and considerations we have consolidated. Of the 161 publications, 15 are reporting guidelines/checklists, 44 are guidelines/recommendations, 18 are reviews that offer recommendations, 37 are frameworks/models, and 47 are commentaries/editorials that offer recommendations or guidance for preliminary studies. For the narrative summary, wherever possible, we have identified relevant examples across widely used study designs for PFS which range from “N of 1” studies, micro-randomized trials, single and multiple group designs, and those involving traditional randomization, to highlight the universality of the consolidated considerations.

Intervention design

Adaptations and tailoring.

Adaptations and tailoring refer to any deliberate changes to the design or delivery of an intervention, with the goal of improving fit or effectiveness in a given context [ 16 ].

Considerations

Where components of the intervention are adapted/tailored, details of who was involved (e.g., investigative team, key stakeholders, participants) in the decisions (see 1.3. Stakeholder Engagement and Co-Production ), when the adaptations/tailoring occurred, and how and why the modification(s) were made need to be clearly reported.

How the proposed adaptations/tailoring address the issues/challenges observed in the intervention need to be clearly reported along with justification for why these changes should result in an improved design.

Whether the adaptations/tailoring occurred a priori or during the conduct of the study should be clearly described.

The intervention component of PFS can be conducted in a rigorous fashion yet be flexible enough to allow for minor adaptations or tailoring (in composition, format, design, etc.) when justified and in response to emerging feasibility indicators.

If substantial adaptations are made to the intervention, such that the adaptations may influence feasibility indicators or behavioral outcomes, re-testing of the PFS prior to progression is justifiable (see 2.1. Iteration and Intervention Refinement ). Adaptations/tailoring occurring under these circumstances should refer to any a priori progression criteria specifications (see 2.2. Progression Criteria ).

Often, existing evidence-based interventions are modified (i.e., adapted/tailored) for delivery to a new sample or in a new setting that is different from where the intervention was originally implemented and evaluated. In these situations, a PFS may be conducted to establish whether the modifications are appropriate in the new sample/setting [ 17 , 18 ]. Adaptations are often made to increase relevance and participant engagement, with the assumption the adaptations would lead to better outcomes in the target populations and settings of eventual interest [ 19 , 20 ].

Adaptations can consist of changes to intervention materials to make them culturally relevant to the target population (race/ethnicity, country/setting, norms/values) [ 19 , 21 ]. Adaptations may also include changes to the intervention itself, such as how it is delivered (e.g., combining sessions, online vs. face-to-face), delivery location, who it is delivered by, or the length of the sessions/intervention [ 22 , 23 ]. Adaptations may occur at any point in the design, implementation, and evaluation/interpretation of a PFS. These include a priori adaptations of existing interventions, those that occur as a result of the evaluation of an intervention, or adaptations made on an ongoing basis throughout a PFS [ 19 , 21 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ].

Where adaptations/tailoring occur, reasons for the adaptations and who participated in the decision-making process should be reported. Often, the adaptation process includes coproduction/codesign methods that can involve focus groups, feedback sessions, and key patient, participant, and public involvement [ 17 ] to justify and inform the relevancy of the adaptations [ 19 , 34 , 35 , 36 ] (see 1.3. Stakeholder Engagement and Co-Production). If coproduction/codesign methods are used, these should be clearly reported.

Site selection and context

Site selection refers to the location in which a PFS will be conducted. Context refers to the factors that form the setting of the intervention, including location, culture, environment, and situation [ 12 , 37 ].

Whenever feasible, researchers should choose sites for PFS that are representative of those anticipated in the future larger-scale trial.

Purposeful selection of sites can be used to ensure an intervention is tested in an appropriate range of contexts.

A rationale for the sites selected should be clearly stated along with how the sites and context reflect what is anticipated in the future larger-scale trial.

Key characteristics of the sites and context should be reported.

The context of intervention delivery and any information that suggests contextual elements may impact the feasibility or future efficacy of the intervention should be clearly reported.

Where context is known or hypothesized to influence the implementation and/or feasibility of an intervention, including more than one site may be necessary.

Setting and contextual characteristics are known factors that can influence intervention outcomes. For PFS testing interventions that rely on a setting as part of the delivery process or are embedded naturally within existing settings, site selection and context become key factors to understand at the early stages of the design and evaluation of an intervention. Setting and context may represent static (e.g., hospital serving low-resource area) or dynamic (e.g., weather, day-to-day variability) characteristics [ 38 ]. Reasons why sites are selected in a PFS can include a range of pragmatic considerations. These include the need for representation of a diverse range of characteristics (e.g., geography, populations served), facilities/infrastructure required for the project (e.g., cell phone connectivity, low-resource settings), and proximity to the investigative team [ 39 , 40 , 41 , 42 , 43 , 44 , 45 ]. These decisions may also be based on the ability to refer sufficient numbers of participants at a given site [ 43 , 46 , 47 ]. Descriptions of the context and setting and how these might influence intervention outcomes should be clearly reported [ 38 , 48 , 49 ].

In some PFS, understanding setting complexity and how an intervention fits within a broader system may be the primary research questions that need to be answered prior to conducting a larger-scale trial. Studies investigating setting or context are useful for the identification of whether an intervention is appropriate or feasible to deliver for a given setting [ 50 , 51 , 52 , 53 ]. This allows for understanding uncertainties about the setting and how differences across settings may influence implementation [ 54 , 55 , 56 , 57 ]. In some situations, where an existing intervention is adapted to be delivered in a different setting, understanding how the intervention interacts with the new context becomes a key feasibility outcome to evaluate.

Stakeholder engagement and co-production

Stakeholder engagement and co-production refers to the use of partnerships with individuals, communities, and service providers to aid in the development and implementation of an intervention [ 58 ].

PFS should be, whenever possible, co-designed/co-created or informed by key stakeholder (e.g., community and professional) perspectives throughout all stages of design and implementation.

Whenever possible, pro-equity approaches that ensure the unique considerations and perspectives around an intervention’s acceptability, safety, etc., and participation in and ownership of research from minority and vulnerable populations, should be used.

The processes by which the PFS was co-designed, including who was consulted, why, when they were consulted, and how their input was obtained, should be clearly described.

Stakeholder engagement and co-production methods are commonly used in PFS to ensure the relevance of a number of intervention-related facets. These include the relevance of intervention materials, how an intervention is delivered, whether the content is appropriate, and if any important components are missing [ 59 , 60 , 61 ]. Employing stakeholder engagement and co-production methods can be useful to ensure ownership of the developed intervention by recipients and end-users [ 62 ]. Where these methods are employed, it is important to report who is involved in co-production (participants, interventionists, members of the public, other key stakeholders) and a rationale for their involvement in the process [ 63 , 64 , 65 ]. The process of engaging stakeholders in co-production can take many forms, including “think aloud”—commonly used for useability testing, questionnaires, and/or interviews [ 66 , 67 , 68 , 69 , 70 ]. What participants did during the co-production process, such as reviewing qualitative interviews or initial testing of intervention materials, should be reported. Details of how participants were engaged in the co-production (e.g., time dedicated, number of rounds of review/workshops, the total number of individuals involved) should also be included [ 71 , 72 ]. In some instances, it may be appropriate to describe details of the training required to facilitate a co-production process [ 61 ].

Theory usage

Theory usage refers to the utilization of any conceptual or theoretical model to inform aspects of the PFS that are mechanisms of change [ 8 ].

Researchers, where relevant, should include details about one or more behavior change theories (e.g., intervention activities, mechanisms) which informed aspects of the PFS, including whether components of the intervention are theoretically or practically informed.

The theoretical foundation of an intervention should be clearly stated. The components of an intervention may directly map on to one or more theories of change. These could be specific theories, mechanisms, or conceptual frameworks informed by practice. Theories of change should refer to intervention resources, activities, mechanisms, and intermediate and final outcomes. This information can be presented in the form of a logic model of change or conceptual frameworks depicting the theory of change or program theory [ 50 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 ]. Details of the theory of change and how this informed intervention development can be presented alongside pilot and/or feasibility outcomes, but could also be published separately, such as in a protocol overview [ 81 , 82 ].

Well-defined problem and aims

Well-defined problems and aims refers to the focused research questions/objectives used to guide the design, conduct, and analyses of PFS [ 8 ].

PFS should be guided by clear and focused research questions related primarily to the feasibility of the intervention and prospects of subsequent scale-up to a larger-scale trial. These well-formulated research questions should be answered by an appropriate and transparent methodology that uses both quantitative and qualitative data.

Where appropriate, the PFS proposal and report should define a clinically important public health problem for which researchers are designing, refining, or adapting an intervention.

PFS are designed primarily to answer key aspects regarding the feasibility of an intervention. These include addressing uncertainties about the intervention and the implications of the findings for larger-scale trials [ 83 ]. Questions of uncertainty are the basis for well-defined problems and aims of PFS. These can include understanding researchers’ access to the population of interest (recruitment); acceptability of randomization (for certain study designs); developing, refining, and finalizing intervention protocols; acceptability of the intervention for the target population; intervention deliverers and other key personnel; and other feasibility-related outcomes including fidelity, cost, equity, and cultural appropriateness [ 70 , 84 , 85 , 86 , 87 ].

In certain situations, the aims of a PFS can be more exploratory in nature. But this does not preclude the study from having a set of well-defined problems and aims. Examples may include learning about the assets, values, and/or history of the community in which an intervention could potentially be delivered and learning about the processes in which co-design and collaboration with community members could naturally take place prior to delivering an intervention.

Study design

Iteration and intervention refinement.

Iteration and intervention refinement refers to the re-testing of an intervention in PFS to further refine intervention components before scaling to a larger trial [ 88 ].

If the conclusion of the PFS is to make significant adjustments to either the study design or the intervention, then it should be acknowledged that the results do not justify proceeding further and a second PFS is necessary to establish feasibility before testing the intervention in a larger-scale, well-powered trial. Any potential changes (adaptations/tailoring) should be clearly documented along with information about how and why the changes are to be made (see 1.1. Adaptations and Tailoring ).

The decision to conduct multiple iterations of a PFS can be pragmatic or theoretical and based on factors including the perceived confidence the redesign will sufficiently address the identified problems.

Conclusions from a PFS should include whether the intervention, in its current form, is ready for a future trial or if modifications are needed (and if so, details of them), and whether they are substantial enough to warrant another PFS.

Iterations refer to the re-testing of an intervention in another PFS [ 89 , 90 , 91 , 92 ]. This can be done based upon findings from a previous PFS trial where minor and/or major adjustments to the intervention, its delivery, or other aspects of the study were found. Initial evaluations of an intervention may even pre-plan for multiple iterations. The iterations create a sequence of trialing and modifying prior to any well-powered trials. At the conclusion of a PFS, investigators can make the decision, based upon progression criteria and other findings, whether additional testing of the intervention needs to ensue prior to scale-up. This decision should be left to the interventionists and co-developers and be based on the evidence collected from the PFS, available resources, and time. Decisions can be pragmatic but also important are theoretical considerations that can inform whether or why alterations to the intervention may or may not result in anticipated or unanticipated changes.

Progression criteria

Progression criteria are a set of a priori benchmarks or thresholds regarding key feasibility markers that inform decisions about whether to proceed, to proceed with changes, or not to proceed from the PFS to a future study, either a main trial or another PFS [ 15 ].

PFS should include a set of progression criteria which are used to inform decisions about whether to proceed, proceed with changes, or not to proceed to a larger-scale study.

Progression criteria should be determined a priori and be based on either evidence from previously published/conducted research or a sound rationale provided.

Decisions on whether to proceed should also be informed by contextual, temporal, and partnership factors that evolve over the course of the pilot and/or feasibility.

Progression criteria should be made for feasibility metrics such as recruitment rate, retention/drop-out rate, acceptability, implementation/fidelity, and other appropriate feasibility indicators where appropriate.

Progression decisions can also include evidence of potential impact (see 5.2. Preliminary Impact ).

Progression criteria decisions can be in the form of a “Go/No Go” system or a “Stop Light” (red/amber/green) system, indicating no progression, progression with changes, or progression with no changes.

Deviations from the application of progression criteria may be justified if researchers are confident that a proposed solution will address the problem at a larger scale and can provide strong theoretical and/or empirical evidence to support their assertion (see 1.1. Adaptations/Tailoring ).

Across all feasibility metrics, some form of progression criteria thresholds and classification systems should be pre-defined [ 74 , 80 , 93 , 94 , 95 , 96 , 97 , 98 ]. The thresholds are commonly study- and intervention-specific, and these thresholds can be designated by investigators and any co-designers. Common classification schemes include red/amber/green and go/no-go. Often, these criteria are pre-registered and/or appear in protocol documents. Progression criteria can be used to gauge whether certain aspects of the intervention and its delivery along with other aspects of the study need to be modified. This information can be used to inform decisions about whether a subsequent test of the intervention should be conducted in another PFS (see 2.1. Iteration and Intervention Refinement ).

Randomization and control groups

Randomization refers to the process of using random chance to allocate units (individuals or settings/clusters) to one or more intervention conditions. Randomization can be used to separate units into distinct groups or randomization within a unit for when and what intervention(s) they may receive (order and timing). A control/comparator condition serves as the counterfactual. A control/comparator group is a group of participants (and/or settings/clusters) allocated to receive differing amounts, orders, or types of intervention(s) being tested [ 99 , 100 , 101 ]. A baseline period can serve as a control/comparator condition for studies employing single-arm or individual-level interventions (e.g., N-of-1) [ 102 ].

Not every PFS needs to include two or more groups or employ random allocation.

The presence of a control/comparator group or randomization can be included if it reflects the aims and objectives of the study.

Control groups can take numerous forms and should be reflective of the objectives of the study, the context within which the intervention is tested, and acceptability by the target population.

When randomization is employed, methods of randomization should be clearly described to ensure reproducibility.

If a control/comparator group is present, feasibility indicators collected on the intervention group should also be collected on the control group where appropriate (e.g., feasibility of data collection, acceptability of randomization, retention).

PFS can employ a range of designs. These include N-of-1 [ 103 ], micro-randomized trials [ 104 ], single-group [ 105 ], quasi-experimental [ 106 ], and multi-group/multi-setting designs [ 107 ]. Despite these design options, not every PFS needs to employ randomization or include more than one group. The use of randomization and multi-group design features should be based on the objectives of the PFS. Randomization in PFS can take the form of allocating groups to different interventions or varying levels of the same intervention (doses). Randomization can also take the form of within-person or group allocation of the timing and/or varying interventions participants may receive. Where multiple groups are included, “what” they receive (i.e., allocated to) should be based on the nature of the intervention and be consistent with conventions within the field of study. This can range from a purely no-treatment comparator to standard practice to alternate active interventions. Where some form of a comparator group is used, researchers should evaluate feasibility metrics to understand such things as the ability to retain those not receiving the intervention and acceptability of randomization. Incorporating either randomization or multiple groups can increase the scientific rigor of the PFS but is not necessary to evaluate most feasibility metrics of an intervention.

Scale-up refers to the process of delivering and evaluating an intervention in progressively larger studies, beginning with testing an intervention within one or more PFS and moving towards larger studies of the same, or similar, interventions. It is a “deliberate effort to increase the impact of successfully tested health intervention so as to benefit more people and foster policy and program development on a lasting basis” [ 108 , 109 ].

PFS should be designed with the intent for future testing of an intervention in large-scale trials and beyond.

Researchers should consider plans for later-phase research on the intervention and explain how information gathered from the PFS will be used to answer key questions surrounding the uncertainty of the intervention or the design or conduct of a progressively larger future study.

Issues regarding the adoption, implementation, and maintenance of the intervention over progressively larger studies can be considered at both the design and conduct phases of the PFS.

Efforts should be made to ensure key features of the PFS be similar to those in the future large-scale trial. These include the amount of support to implement the intervention, characteristics of who delivers the intervention, the target population, the duration under which the intervention is tested, and the measures employed.

Where differences are anticipated between pilot and/or feasibility testing and the larger-scale trial, a description of these differences should be provided along with a clear justification of how the changes may or may not impact the intervention.

PFS should be designed and conducted with the idea the information collected will be used to inform the testing of an intervention in progressively larger sample sizes and/or settings [ 85 , 110 , 111 , 112 , 113 , 114 , 115 , 116 ]. This implies researchers who conduct PFS intend to continue to refine and optimize an intervention for maximal impact along a translational science continuum [ 117 , 118 , 119 ]. With this in mind, understanding early on how an intervention could be delivered to progressively larger numbers of individuals and/or settings should be incorporated into the early stages of the design and conduct of PFS. Considerations for scaling can include characteristics of those who deliver an intervention, the resources required to train and deliver an intervention, and to whom an intervention is delivered. How these aspects can change as one progresses from commonly smaller-sized PFS to evaluating an intervention for broader population-level impact should inform what transpires in a PFS. Researchers should, therefore, consider whether what they can accomplish on a smaller scale can similarly be accomplished on a larger scale [ 120 , 121 ].

Conduct of trial

Measurement and data collection

Measurement and data collection refer to any tools, devices, instruments, personnel, and time required to assess feasibility or outcomes related to an intervention.

PFS can assess the feasibility and appropriateness of measurement and data collection procedures including the following:

How or if the data can be collected

The acceptability of the measurements and data collection procedures (e.g., burden)

If the measures are valid for the population/outcomes in question

Where applicable, measurements and data collection procedures should closely resemble those anticipated for the well-powered trial.

The reporting of measurement and data collection procedures should be sufficiently detailed to permit standardized data collection, including information about why the measurements were selected and how they were administered, scored, and interpreted.

Information about the feasibility and appropriateness of measurement and data collection procedures can consist of both quantitative and qualitative data sources.

The process of collecting outcome data in a PFS serves to demonstrate the feasibility of data collection methods—whether explicitly stated or not [ 122 ]. However, some PFS may be designed to answer whether outcome measures proposed for the larger-scale trial can be collected. This can include the ability to collect data using more invasive/burdensome methods (e.g., urine/hair samples, blood draws) [ 123 , 124 ]. Additional metrics associated with the feasibility of measurement and data collection may include determining rates of missing data, participant response rates, and any time/resource costs associated with data collection [ 125 , 126 , 127 ]. This information can be used to reduce participant burden and costs associated with data collection as well as refine protocols in the larger-scale trial [ 128 , 129 , 130 , 131 , 132 , 133 , 134 , 135 , 136 ].

Recruitment

Recruitment refers to the procedures used to identify and select potential participants (individuals and/or settings/clusters) and enroll them into a PFS. The recruitment rate is the proportion of eligible participants or settings/clusters who are enrolled at the baseline of an intervention trial compared to the invited/eligible target population [ 137 ].

Recruitment procedures should be clearly described, with any strategies designed to maximize recruitment fully detailed.

Information should include details of procedures used to recruit at the individual and setting/cluster levels, where appropriate.

Recruitment information should include the following, where appropriate:

Proportion of eligible units (e.g., individuals, settings) recruited

The start and end dates of the recruitment periods

Number of participants recruited per setting/cluster, overall, and number of settings/clusters

Number of potential participants screened, eligible, consented, and enrolled in the study

Reasons for non-recruitment/non-consent

Acceptability of recruitment strategies

Details should be provided about the recruitment strategies used, measures of their success, what worked, and what may need to be altered for future studies.

Participant recruitment is a key marker of intervention feasibility. Identifying optimal recruitment strategies in a PFS plays a critical role in determining whether the specified sample size can be achieved in the well-powered trial. Recruitment strategies may include opt-out methods (passive consent), telephone reminders, open designs (participants know what arm of the trial they are in), referrals, modalities of communication with potential participants (e.g., phone calls, emailing, text, mailings), convenient study location, and partnering with community members/settings [ 138 , 139 , 140 , 141 ]. The specific recruitment strategies used can influence the demographic makeup of participants. Different recruitment strategies can also yield varying amounts of eligible participants. In addition, each recruitment strategy has an associated cost. It may also be important to identify reasons why participants refused to participate in the study and record these reasons quantitatively and/or qualitatively. This information should be collected at the individual and/or setting level where appropriate. These can be important to establish during a PFS to optimize recruitment procedures in the larger-scale trial, especially in situations where there are uncertainties around recruiting the target population. At times, it may even be appropriate to formally test recruitment strategies, particularly when there is uncertainty about the best approach. For example, by embedding a “Study Within A Trial” (SWAT), researchers may gain answers to uncertainties around methodological decisions regarding a number of feasibility outcomes, including recruitment [ 142 , 143 ].

Retention (attrition/drop-out) is the proportion of enrolled participants who are present throughout the full length of the intervention [ 137 ].

Researchers conducting PFS should ensure retention rates are measured.

Where possible, assessments can be made to identify differences in retention across groups or intervention conditions.

Reasons why individuals leave a study can be collected and analyzed to investigate whether particular factors are associated with retention.

Procedures should clearly describe strategies used to assist with retaining participants during the delivery of the intervention and any post-intervention follow-up time periods, where appropriate.

Retention-related information can include both quantitative and qualitative data sources.

Retention is a commonly assessed marker of intervention feasibility. Retaining participants throughout an intervention is important to ensure participants receive the full dose of intervention components as designed and whether selective attrition is present. Retention-related information also helps to understand issues regarding missing data and low statistical power in future studies. Ultimately, retention is a marker of intervention viability. In other words, if participants do not want to receive an intervention it is unlikely to be impactful.

For a given intervention, a clear definition of retention should be reported. This can include participants staying for the duration of study-related procedures/measures (e.g., data collection), completing intervention components, and/or attendance at intervention sessions [ 22 , 92 , 128 , 144 ]. Depending on the nature of the intervention and the outcomes targeted, PFS may be designed specifically to address issues regarding retention in samples that have been historically challenging to engage/retain in interventions [ 145 , 146 ].

Retention strategies, such as flexible scheduling, reminders, compensation, consistency in study staff (continuity of relationships), gathering multiple contacts, thank you and birthday cards, and follow-up phone calls within a given period, can reduce the rate of participant drop-out [ 139 , 147 , 148 , 149 ]. Where dropouts occur, reasons for withdrawal from the study can be collected [ 128 , 150 ]. Factors influencing retention, both positively and negatively, including participant motivation/aspirations, expectations, the perceived need for an intervention, and accessibility of intervention (location delivered), can be collected from both participants and intervention deliverers [ 151 , 152 , 153 , 154 , 155 ].

Implementation of intervention

Acceptability.

Acceptability is a perception/notion that an intervention or various aspects of an intervention are favorable, agreeable, palatable, enjoyable, satisfactory, valued, appropriate from the perspectives of participants or communities receiving the intervention, and/or have a wider fit within a system. It relates to how users “feel” about an intervention [ 156 ].

Researchers should clearly define what is meant by “acceptability” for a given study, at what levels (e.g., individual, deliverer, setting) it will be assessed, and by what methods (e.g., surveys, interviews). This should be based on the nature of the intervention and its constituent components, target population, setting level characteristics, and key stakeholders.

Measures of acceptability can be pre-defined and included in both the PFS and large-scale trial stages.

Acceptability should be captured, at minimum, from the end user (intervention participants). Acceptability can also be captured from those involved with delivering the intervention, along with anyone else involved in the implementation process.

Acceptability, as defined for a given study, can be assessed for participants in control conditions where appropriate (e.g., acceptability of randomization to active comparator, acceptability of data collection procedures).

Researchers can use both quantitative (e.g., surveys) and qualitative (e.g., interviews) methods to assess acceptability.

In most behavioral interventions, it is important to understand whether those receiving an intervention, those delivering an intervention, and any other key individual(s) find the intervention, either in its entirely or in relevant parts, to be “acceptable” to inform whether the intervention would be used or tolerated. Acceptability encompasses a range of aspects related to impressions of an intervention. These can be gathered anytime along the intervention development continuum. At the earliest stages of conceptualization, prior to packaging and preliminary testing of an intervention, assessments of acceptability (preferences) can include participants’ views of whether the proposed intervention could be appropriate for addressing a given outcome, whether they (the participants) would be willing to adhere to an intervention, the suitability of intervention materials, or whether they perceive the intervention to be useful. During intervention delivery, ongoing assessment of likeability, satisfaction, metrics of engagement with an intervention, and utility can be collected periodically [ 45 , 157 , 158 , 159 ]. Once an intervention is completed, post-assessment markers of acceptability can include perceptions of the length or overall burden of the intervention, what strategies/components of an intervention were liked best, referral of the intervention to others, or whether the intervention met their (the recipients, deliverers, others) preferences/expectations. Where an intervention is delivered by individuals outside the intervention-development team, assessing their perspectives on the acceptability of an intervention may be necessary.

Assessments of acceptability can include both qualitative and quantitative measures. User-centered design [ 160 ] and “think aloud” protocols [ 161 ] can be used in the early stages of intervention conceptualization/formulization. Exit interviews, upon intervention completion, from recipients, deliverers, and other key individuals involved in the intervention, are often employed to evaluate markers of acceptability. Quantitative measures typically include items developed specifically for a given study. Alternatively, existing scales assessing acceptability can be used or modified accordingly for a given application [ 162 , 163 , 164 ]. Acceptability can also cover other aspects of the evaluation process of an intervention. This includes such areas as whether completing the proposed measures is feasible, acceptability of being randomized, or whether recipients were satisfied with the location where an intervention was delivered.

Fidelity is the degree to which an intervention is delivered as intended and the quality of that delivery [ 165 , 166 ].

Researchers should clearly define what is meant by “fidelity” for a given study, at what levels (e.g., individual, deliverer, setting) it will be assessed, and by what methods (e.g., surveys, interviews).

Measures of fidelity should be pre-defined with all intervention components listed.

Fidelity can consist of information about how an intervention will be delivered, for whom, what the intervention consists of, and when and where (context) the intervention will be delivered.

If strategies are used to encourage fidelity (e.g., a manualized intervention, feedback to those delivering the intervention), these should be reported.

Factors influencing fidelity can be assessed and, where appropriate, linked to feasibility outcomes.

Fidelity is often a primary marker of implementation. Assessment of an intervention’s fidelity provides key information regarding whether an intervention, either the testing of individual components or in their entirety, can be delivered as intended. In PFS where initial evaluations of an intervention are conducted, fidelity plays an important role in identifying whether the intervention can be delivered as intended. Evaluation of fidelity implies a working understanding of the intervention and some pre-planned, a priori expected delivery [ 167 , 168 ]. Measuring fidelity can be useful where adaptations (or changes) to the materials may take place (either planned or unplanned). Systematically documenting deviations from the original intervention can yield important insights into whether adaptations were beneficial or detrimental to the outcomes [ 169 ].

Fidelity can include many aspects of an intervention. These include adherence to intervention materials (what was done), quality of delivery (how it was done), and the dose of what was received [ 166 , 170 ]. Assessing fidelity can take many forms. This includes the creation of study-specific fidelity checklists which capture the presence of key components that should be delivered during an intervention (e.g., key material to be delivered in session one or a multi-session intervention) and how they were delivered [ 134 , 171 ]. Response ranges vary from present/absent, yes/no, to Likert-scaled items. Fidelity checklists can be completed either in real-time or reviewed later through the use of recorded video or audio of completed sessions [ 172 , 173 , 174 ]. Checklists can be completed by either someone external to the delivery agent via structured observations/recordings or completed by the delivery agent (e.g., self-report, logbooks) immediately following the delivery [ 175 , 176 , 177 ].

Qualitative interviews of delivery agents can also be conducted to gauge views regarding aspects of an intervention such as the training received to deliver, confidence in delivering, and any perceived barriers to delivering an intervention as planned [ 172 ]. Factors affecting fidelity can be collected to understand what, if anything, may influence departures from delivering an intervention as designed [ 22 , 132 , 173 , 178 ]. Common ways to encourage fidelity are through the use of a manualized package of procedures, training materials, and ongoing review of sessions accompanied by feedback.

Cost and resources

Costs and resources refer to the investments and assets required to develop, implement, and sustain an intervention [ 12 , 179 ].

PFS can include assessments of the costs and required resources of conducting an intervention.

In PFS costs and resources mIn PFS costs and resources may include the following:ay include the following:

Monetary costs associated with training, supervision, and recruitment of both stakeholders and participants, incentivization, facilities, materials, and intervention component development and delivery.

Opportunity costs/time demands associated with completing the intervention by participants and delivering the intervention by providers.

Researchers can collect information to determine the feasibility of measuring the costs associated with the intervention, with this information used to inform a more well-defined cost analysis/economic evaluation in a larger-scale trial.

Researchers should keep in mind that some costs associated with the intervention will be fixed (one-time costs) and some will be recurring during the successful scale-up and sustainment of the intervention.

For some PFS, collecting the costs associated with delivering an intervention may be necessary to inform a larger-scale trial. In PFS, this is often referred to as conducting an economic evaluation, costing, or cost analysis [ 125 , 180 , 181 , 182 , 183 ]. Studies may collect cost data to “rehearse” cost-effectiveness evaluations (economic evaluations) or evaluate the feasibility of collecting cost-related data [ 169 , 184 ]. Where cost data are collected, micro-costing approaches that inventory all associated costs with an intervention are often conducted and used to generate a total cost per unit estimate, often expressed as a cost per participant. Costs can be fixed, variable, or projected future estimates, and they may vary according to the desired fidelity and rigor of the implementation of the interventions. Common resources inventoried for cost include the costs of consumables, staff time, services received, transportation, room hires, and refreshments. Costs can be separated into the costs associated with the initial design/development, set up of the intervention, training of staff to deliver, and the costs associated with intervention delivery. The inclusion of cost data is not study-design specific and spans a wide range of designs from N of 1 to cluster randomized studies [ 185 , 186 , 187 ].

Statistical analysis

Sample size.

Sample size refers to the number of participants (or groups/clusters) in a given study [ 188 ].

The sample size of a PFS should be based on the feasibility objectives of the study.

Sample sizes do not have to be based upon a formal sample size calculation (i.e., power).

Sample sizes should be pre-specified and justified.

Sample size estimates should consider the representativeness of the target population or subgroup, setting, and other relevant contextual aspects that may influence how and why an intervention works.

Sample characteristics should be clearly described and may refer to individuals and/or clusters (e.g., churches, workplaces, neighborhoods, schools).

Where relevant, studies should clearly report factors impacting the sample size (e.g., availability of funds, time constraints).

Investigators are encouraged to report the a priori power achieved by the sample size selected for a PFS.

It is widely recognized that most PFS are underpowered to detect clinically significant/public health important effects in outcomes. Selecting the appropriate sample size for a PFS, however, can vary across studies based on the objectives. In some instances, formal power calculations can be conducted/presented, but one should avoid the temptation of presenting a PFS as being well-powered by assuming implausibly large effects and/or event rates and using non-relevant outcomes. Sample size justification can be made based on other factors including, but not limited to, the availability of resources, the number of potential participants within a given setting, representativeness of the sample to the target population, complexities regarding the intervention, or the experiences of the investigators working with the population/setting [ 189 , 190 , 191 , 192 , 193 ]. Regardless of the approach taken, researchers need to ensure they have sufficient numbers (i.e., sample size) to make informed decisions based on the feasibility metrics and objectives of a PFS and acknowledge any limitations that the usually small sample size confers.

Preliminary impact

Preliminary impact is the ability of an intervention, during a PFS to produce a desired or intended result [ 194 ].

PFS need not be powered to detect statistically significant differences in outcomes, but one or more outcomes, as appropriate to the research, can be assessed.

When outcomes are collected, changes in outcome data (e.g., estimated effect sizes) can be used to aid in decisions regarding the conduct of a subsequent larger-scale trial (e.g., sample size needed).

In many cases, it may be necessary to demonstrate an intervention “moves” outcomes in the appropriate direction and is not causing harm. In this scenario, it is recommended statistical testing can be performed but to avoid the interpretation of p values as conclusive evidence of an intervention’s impact in a larger-scale trial.

Interpretations of performed statistical tests should not include a justification for (or against) proceeding to a subsequent large-scale intervention or for making claims about the likely success of the study. Interpretations should help guide, but not dominate, the decision to proceed to a large-scale intervention.

Investigators should avoid misusing language such as “statistically significant” to describe their interpretation of outcomes from a PFS.

Where pilot and/or feasibility estimates of impact on primary, secondary, or tertiary outcomes are reported these should be pre-specified, with point estimates and a measure of variability reported for all time points.

For studies presenting both feasibility and outcome data, outcome data should be relegated to a secondary or exploratory focus.

In some circumstances, it may be appropriate to evaluate, in a preliminary/exploratory fashion, the potential impact of an intervention on proximal or distill outcomes in a PFS. Where outcomes are assessed and reported, researchers need to understand the evidence is neither definitive nor necessarily very indicative of an intervention’s impact within a larger-scale trial. Nevertheless, the evaluation of outcomes within a PFS can provide useful, additional information to help inform decisions about whether the intervention is ready to be tested at a larger scale. When reporting outcomes, researchers should avoid using misleading language centered on the presence or lack of “statistical significance”. All reported outcome assessments should be secondary to feasibility metrics, which are the primary focus of most PFS. Further, it is suggested that journals should not require by default outcome assessments and/or formal hypothesis testing for manuscripts that report on PFS nor base publishing decisions on the outcomes of potential efficacy analyses if reported.

Pre-registration and protocol publishing

Pre-registration and protocol publishing refers to an a priori process of documenting planned intervention design and analyses [ 195 ].

Pre-registration and a protocol made publicly available (via peer-reviewed journal, pre-print server, or other forms of public dissemination) contributes to transparency and ensures that changes between what is planned, what is conducted, and what is ultimately reported are communicated and justified.

We acknowledge there is a certain degree of flexibility when it comes to PFS between what is proposed and what actually transpires in the execution of the study. Pre-registration of PFS needs to balance the developmental/exploratory nature of these types of studies with the need to document and adhere to general protocols that are the foundation of rigorous and transparent science. The goal of pre-registration is not to create an inflexible scope of work that cannot adapt to uncertainties encountered in the study, but to communicate changes to a protocol and to justify why those changes were made.

Pre-registration of study objectives can be appropriate and at times required based upon funding stipulations. While some PFS are not pre-registered, many can be found on existing trial registries. These include Clinical Trials [ 196 ] and other emerging pre-print servers and open-science repositories, such as Open Science Framework [ 197 , 198 ]. Protocol publishing is also becoming increasingly common for PFS. Pre-registration and protocol publishing may help to provide details about a PFS as well as ensure deviations, although necessary at times, are clearly documented.

Study labeling

Study labeling refers to naming/presenting a PFS with appropriate naming conventions for the study being conducted [ 2 , 3 ].

At a minimum, researchers should make sure studies are clearly labeled to indicate their preliminary nature and reflect the aims and objectives of the study in both the title and abstract with either “pilot”, “feasibility”, “proof-of-concept”, “formative”, or other relevant label(s).

PFS should be clearly labeled to identify and separate them within the intervention development and evaluation literature. One of the benefits of clearly labeling PFS is the ease of identification of these types of studies to understand the evolution of behavioral interventions. Because PFS are often smaller in scale, clear identification also helps to distinguish these types of studies from studies that are small in scale and lack an emphasis on intervention development, refinement, and scaling.

A number of different taxonomies have been proposed to label these types of studies. However, we recognize researchers can and do use terms referring to preliminary studies interchangeably or utilize a combination of them to describe a single study [ 79 , 136 , 167 , 199 , 200 , 201 , 202 , 203 , 204 , 205 , 206 , 207 , 208 , 209 , 210 ]. In the absence of a universal consensus of terms, it is recommended investigators clearly label their PFS with one or more widely used terms that identify the preliminary nature of the study. These terms could include “pilot”, “feasibility”, “proof-of-concept”, “preliminary”, “evidentiary”, “vanguard”, and/or “exploratory”. Thus, investigators should identify the most appropriate term(s) that describe the objective of their study. This should consider the stage and number of tests/evaluations of an intervention.

Framework and guideline usage

The utilization of published frameworks/guidelines to guide the development, implementation, and reporting of PFS.

Where possible, researchers should choose an appropriate framework to structure PFS and use it to guide the design, conduct, analysis, and reporting of said study.

Findings from PFS should be disseminated in a way that adheres to reporting guidelines to facilitate transparency and allow for replication.

There are many existing guidelines, checklists, frameworks, and recommendations that can be useful for the design, conduct, implementation, analysis, and reporting of PFS [ 9 , 211 ]. The use of these publications is associated with higher study quality and reporting [ 9 ]. Guidelines include those developed specifically for PFS and also include those designed outside of the preliminary study context but are highly relevant to many aspects of PFS. Investigators should be familiar with existing guidance and utilize it appropriately, based on the specific objectives of their PFS.

PFS play a pivotal role in the development, refinement, implementation, and sustainability of successful behavioral interventions. This is evidenced by their emphasis on funding agencies [ 4 , 212 , 213 , 214 , 215 , 216 ] and depiction within translational science frameworks [ 117 , 118 , 217 , 218 ]. We identified 161 publications offering some form of guidelines, checklists, frameworks, or recommendations for PFS. Through a Delphi study utilizing expert perspectives, we developed a comprehensive set of considerations which span the continuum of development, conduct, implementation, evaluation, and reporting of behavioral intervention PFS. We believe this will serve as a valuable resource for researchers in the behavioral sciences.

Continued challenges with PFS

While this consolidation of considerations for PFS was developed for broad applicability, there were strong opposing views among the Delphi study participants on some of the considerations that represent continued challenges with PFS. The most striking opposing opinions were observed within the “statistical analysis” theme and were present in both the “sample size” and “preliminary impact” considerations. For example, several respondents in the Delphi study believed sample size estimates for a larger-scale trial can be informed by the estimated intervention effect sizes generated from a PFS, and formal hypothesis testing can be performed and associated p values interpreted in a preliminary study. Other respondents expressed strong opinions that the sample of a PFS need not be representative of the target population. Conversely, the vast majority of respondents agreed that sample size justifications should be based on the feasibility objectives of a given PFS and argued against hypothesis testing (i.e., formal statistical testing and interpretation of p values) during the early phases of intervention development. There have been arguments made for reporting confidence intervals instead of p values for any non-feasibility-related outcomes assessed during PFS [ 219 , 220 , 221 , 222 ]. However, respondents of our Delphi study were quick to point out there is little practical difference between the use of p values or confidence intervals, especially if the PFS is underpowered from the start.

Opposing views were identified throughout the Delphi process for other considerations as well, including “study labeling” and “pre-registration and protocol publishing”. For study labeling, some respondents appreciated the distinction between “pilot”, “feasibility”, and other “preliminary study” terminology, while others worried that these distinctions were not well known and may cause undue confusion. Many participants of the Delphi study indicated they would rather there be no distinction, voicing concerns that adopting rigid taxonomies would create research silos and hinder cross-purpose innovation. Ultimately, we chose not to take a definitive stance on this issue, but rather make researchers aware they should be labeling PFS in some way to aid in the identification of these types of studies. On the topic of pre-registration and protocol publishing, some Delphi respondents argued that pre-registration and protocol publishing for PFS was asking too much and that this type of work should be reserved only for larger-scale trials. Others fully supported the idea of pre-registration and protocol publishing for PFS, arguing it aids in transparency and reproducibility. Again, these are decisions ultimately left up to the researchers conducting PFS, but it is likely that registration will be increasingly requested and enforced (e.g., by funders). The lack of registration of all PFS means that one cannot understand the totality of the efforts that are made in that space for developing and assessing the feasibility of an intervention.

It is important to understand that what may be viewed as common and accepted practice may not be widely held everywhere and the reasons for this vary according to country, funder, and disciplinary norms. It may be that differing opinions stem from differences between what commonly accepted/promoted translational science frameworks espouse and the realities of conducting PFS, which are often conducted with limited resources and abbreviated timelines. In addition, there may be different levels of expectations about what is proposed in these frameworks and the expectations of funding agencies and grant reviewers [ 223 ]. Such disagreements can prove problematic for behavioral scientists when seeking funding or wanting to publish findings from their PFS. Reconciliation on these topics is unlikely, and perhaps unnecessary, yet it is important to acknowledge what can and cannot be accomplished by a PFS. We believe appropriately tending to these issues throughout all phases of design, conduct, interpretation, and reporting should help preemptively dissuade critiques that could stymie the progress of intervention development and implementation.

Progress for PFS

While disagreements were noted for a few considerations, most respondents agreed on the content of most topics. For example, participants of the Delphi study agreed that feasibility outcomes, including recruitment, retention, acceptability, and fidelity should take priority over preliminary impact and should be used and presented as the primary outcomes of PFS. This also aligns with developing well-designed problems and aims of PFS, most of which should answer questions regarding uncertainties (feasibility) of an intervention. Respondents also agreed progression criteria are useful when developing and deploying PFS, although some recommended caution on the use of progression criteria that are too rigid when making decisions about scaling up PFS to the next stage. Finally, and perhaps most salient, participants agreed on the importance of PFS as a critical step in successful large-scale intervention development and implementation. However, one cannot exclude the presence of selection bias in favor of the importance of PFS among authors who have authored guidelines on them and even more so among authors who responded to our surveys.

Use of the considerations

We believe the considerations in this paper span the continuum of PFS, from development to reporting, and will be useful for researchers planning to conduct their very first PFS to well-seasoned interventionists. We envision these consolidated considerations being used in practice and as an educational tool for trainees. On a broader scale, we are hopeful this consolidation may improve PFS in the future, reducing research waste and leading to the development of high-quality, scalable behavioral interventions with maximal reach and public health impact. In addition to the considerations themselves, we provide a crosswalk of all published guidelines, checklists, frameworks, and recommendations related to PFS in Additional file 2 in an effort to amplify the voices of experts in this field. Researchers reading this study and those who want to know more about a particular consideration are encouraged to utilize the crosswalk located in Additional file 1 to identify further reading, which may provide more specific guidance on a particular topic. While not the focus of this consolidation, we also believe many of the considerations are cross-cutting with large-scale implementation and dissemination research. Researchers doing this type of work may look to certain considerations to guide aspects of their larger-scale study as well.

Strengths and limitations

These consolidated considerations have several strengths. First, they were created based on information gathered from 161 published guidelines, checklists, frameworks, and recommendations on the topic of PFS. We relied on authors from these very same 161 publications to voice their opinions about the most important PFS-related topics via a three-round Delphi study. The total sample of participants across three rounds of the Delphi process represented over 35% of the 161 publications. Participants had, on average, 23 years of experience since their terminal degree, representing a collective 1150 years of experience across respondents. Moreover, we supplement this consolidation with a review of those 161 guidelines, checklists, frameworks, and recommendations, creating one of the largest collective sources of information on PFS published to date. This study is not without limitations. While we had a moderate representation of Delphi participants across publications, we were only able to recruit 10% (50 out of 496 identified authors) of our target population for the Delphi process. Further, while there was an equal distribution of males and females, the sample was largely White. Other than age and years of terminal degree, we did not collect other demographic information on the Delphi participants, although the median year of publication for the publications represented in our sample was slightly more recent (2015) than the total sample of possible publications (2013) from which authors were sampled. For the considerations themselves, there is still no true consensus on many of the topics presented. Differences of opinion were observed throughout the Delphi process and can be found across the published literature. Despite this, we believe the consolidated considerations could be a valuable resource for behavioral interventionists conducting PFS on a broad range of public health topics.

This is one of the first studies to attempt to garner consensus on a broad range of considerations regarding PFS for the behavioral sciences. We leveraged expert opinion from researchers who have published PFS-related guidelines, checklists, frameworks, and recommendations on a wide range of topics and distilled this knowledge into a valuable and universal resource for researchers conducting PFS. We identified 20 considerations for PFS, which fall into six categories, including intervention design , study design , conduct of trial , implementation of intervention , statistical analysis , and reporting . We also provide a list of the available publications on each of the specific considerations for further reading and use and have aligned these publications with the considerations set forth in this paper. Researchers may use these considerations alongside the previously published literature to guide decision making about all aspects of PFS, with the hope of creating and disseminating interventions with broad public health impact.

Availability of data and materials

The datasets used and analyzed during the current study are freely available at https://osf.io/kyft7/ .

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Acknowledgements

The authors would like to thank all experts who provided valuable input through the Delphi process of this study.

Research reported in this abstract was supported by The National Heart, Lung, and Blood Institute of the National Institutes of Health under award number R01HL149141 (Beets), F31HL158016 (von Klinggraeff), and F32HL154530 (Burkart) as well as by the Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health under award number P20GM130420 for the Research Center for Child Well-Being. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

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Lauren von Klinggraeff, Sarah Burkart, Alexsandra da Silva Bandeira, James F. Thrasher, Xiaoming Li & Michael W. Beets

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CDP - Conceptualization; methodology; software; formal analysis; investigation; data curation; writing—original draft; writing—review and editing; visualization; and supervision. LV—Methodology; investigation; data curation; writing—original draft; writing—review and editing; and formal analysis. SB—Methodology; investigation; data curation; writing—original draft; writing—review and editing; and formal analysis. AB—Methodology; writing—original draft; writing—review and editing; and formal analysis. DL—Writing—original draft and writing—review and editing. RJ—Writing—original draft and writing—review and editing. AO—Writing—original draft and writing—review and editing. ES—Writing—original draft and writing—review and editing. JPA—Writing—original draft; writing—review and editing; and formal analysis. JT—Writing—original draft and writing—review and editing. XL—Writing—original draft and writing—review and editing. MWB—Conceptualization; methodology; software; formal analysis; investigation; data curation; writing—original draft; writing—review and editing; visualization; supervision; and funding acquisition. All authors read and approved the final manuscript.

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Literature crosswalk.

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Summary table of considerations.

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Pfledderer, C.D., von Klinggraeff, L., Burkart, S. et al. Consolidated guidance for behavioral intervention pilot and feasibility studies. Pilot Feasibility Stud 10 , 57 (2024). https://doi.org/10.1186/s40814-024-01485-5

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Received : 20 September 2023

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DOI : https://doi.org/10.1186/s40814-024-01485-5

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