Systematic Review


A systematic review is a review of evidence relevant to a clearly formulated question that uses systematic and explicit methods to identify, select and critically appraise relevant research, and to collect and analyse data from the studies that are included within the review. Authors should note that all systematic reviews published in Environmental Evidence will have been conducted according to the CEE process. Please contact the Editors at an early stage of planning your review. Full guidelines can be accessed here.

For systematic reviews to be relevant to policy and practice they need to be as up-to-date as possible. Consequently, at the time of acceptance for publication, the search must be less than two years old. We therefore recommend that systematic reviews should be submitted no later than 18 months after the search was conducted. We will consider publication of updates of existing systematic reviews, typically from three years since the original search, but earlier if the development of the evidence base justifies the update.

Length up to 20000 words.

Preparing your manuscript

The information below details the section headings that you should include in your manuscript and what information should be within each section.

Please note that your manuscript must include a 'Declarations' section including all of the subheadings (please see below for more information).

Title page

This should list the title of the article. The title should include the review question, for example: What is the effectiveness of intervention A in producing change in subject B? What is the impact of factor X on subject Y? The full names, institutional addresses, and email addresses for all authors must be included on the title page. The corresponding author should also be indicated.


The Abstract of the manuscript should not exceed 500 words and must be structured into separate sections: Background, the context and purpose of the review, including the review question; Methods, how the review was performed and statistical tests used; Results, the main findings, including results of search and assessment of evidence base; Conclusions, brief summary and potential implications for policy/management and research.


Three to ten keywords representing the main content of the article should be given.


The Background section should be written in a way that is accessible to researchers without specialist knowledge in that area and must clearly state - and, if helpful, illustrate - the background to the review and its aims. Reports should indicate why this study was necessary and what it aimed to contribute to the field. A theory of change and/or conceptual model should be presented that links the intervention or exposure to the outcome. The role of stakeholders in the formulation of the question should be described and explained. The section should end with a brief statement of what is being reported in the article.

Objective of the Review

This section should describe the primary question and secondary questions when applicable. The primary question is the main question of the review. The secondary questions are usually linked to possible subgroup analyses. This section may also present definitions of the primary question components (e.g. the subject, intervention and outcome measure) but see ‘study inclusion criteria’ below.


Search strategy

Here the searches are described in sufficient detail so as to be repeatable. Direct citation of the protocol should be made here and deviations from the protocol explained in the appropriate sections. The following subsections are a guide to the detail required on what was searched and how the search was conducted.

  • Search terms and languages. How were decision made on the keywords and languages to be used?
  • Search strings and/or combinations of searches (search strings refer to combinations of terms using Boolean characters, combinations are methods used to set-up and pool different searches run separately). Trial development of search strings may be included as an Additional File.
  • Estimating the comprehensiveness of the search. How did you test how your search performs in terms of identifying all relevant studies?
  • Publication Databases and services to be searched (e.g. Web of Science, Scopus, CAB Abstracts)
  • Internet searches to be conducted (e.g. Google Scholar). Give details of how you will cope with limitations to use of search strings and limiting number of hits considered.
  • Specialist searches - Searches for grey literature: contacts, searches of organisational websites, use of specific search terms or strings, filtering or limitations.
  • Supplementary searches such as Bibliographical searches and literature provided directly by experts or stakeholders

Article screening and study inclusion criteria

Here confirm (or state deviations) definitions followed to include eligible articles based on the following aspects, so that this stage is transparent and replicable by any external reader.

  • Relevant subject(s)
  • Relevant intervention(s)
  • Relevant comparator(s) (if appropriate)
  • Relevant outcomes
  • Relevant types of study design

Confirm or state deviations in the screening process and test(s) for consistency of decision regarding inclusion/exclusion, at title, abstract, full-text level.

 Study quality assessment

Describe here the approach you used to critically appraise and assess quality of included studies. Consideration should be given to ensuring that important aspects of study quality which would influence the reliability of the evidence were taken into account, such as internal validity (freedom from bias or confounding) and external validity (generalisability of a study’s results to the current Systematic Review question).

Data extraction strategy

What categories of data were extracted? Describe here how you collected and recorded outcome data and associated meta-data from included studies. How was the data extraction conducted and how did you test for repeatability?

Potential effect modifiers and reasons for heterogeneity

Confirm or update the list of those effect modifiers considered in the review and details of how the list was compiled (including consultation of external experts).

Data synthesis and presentation

Describe here the methods you used to synthesise the collected data and any subsequent manipulation of the data set, such as sub-group or sensitivity analyses. Narrative synthesis methodology should be described and included studies tabulated as a minimum. Potential for meta-analysis (or alternative form of synthesis) should have been assessed and synthesis methodology justified and fully explained. Test for bias should be conducted where possible.


Results of each stage of the review (e.g. search statistics, inclusion, critical appraisal, data extraction, reasons for variability in the results found and potential confounding factor, if possible summary statistics/quantitative analysis of the papers) should be clearly reported. A flow diagram reporting the inclusion/exclusion process should normally be presented. A narrative synthesis of included studies (usually in tabular form) should always be presented (can be as additional material when appropriate). Results of quantitative syntheses should be fully reported with appropriate figures, tables and statistical values. Subsections should follow the format:

Review descriptive statistics, systematic map (sub-headings as applicable)

Report here the date(s) of the search you conducted, the number of articles found in the search and included at each inclusion level, along with results of tests of repeatability and any action taken. Descriptive statistics should be provided on any relevant information on the distribution of the articles found (e.g. geographical, temporal, institutional) in order to assess potential gaps or bias in the evidence. A mapping of the evidence could be provided here if this was planned as an intermediate step. For full transparency Additional files are expected here including:

  • Tables of how articles (all and included only) were found (i.e. through which search database etc)
  • A list of studies excluded at full text together with reasons for exclusion (this may be a presentation of your screening checklist as described in your protocol).

Narrative synthesis including study quality assessment

For each included study provide a summary of quality assessment as a table. Data extracted, including metadata and findings along with other key information such as location and reporting of effect modifiers should be presented as a table or additional file (this also serves as a list of all included studies). A narrative synthesis will normally be provided as text and/or in tabular form, either in the main body of the paper or as an appendix.

Data synthesis

Report here results of quantitative and/or qualitative synthesis of extracted data. If meta-analyses have been conducted present full details, including effect sizes and related statistics (e.g. tests for heterogeneity) and, if possible, tests for potential bias. Data should have been utilised to their full potential to answer the question.


This section should be relatively brief and speculation limited only to suggestions for further enquiry or analysis (e.g. potential reasons for heterogeneity in outcome). A section on review limitations should normally be included.

Reasons for heterogeneity

A detailed discussion/evaluation of the level of variation in effect of the intervention and possible reasons for these variations including the possible effect modifiers and impact of variation in the study variables such as experimental design.

Review limitations

A detailed discussion of the limitation of the review including limitations due to the search strategy (limitations of the review), as well as limitations due to underling bias within the studies found such as baseline bias and confounding variables (limitations of the evidence base). Gaps in the information provided by the studies should also be highlighted.

Review Conclusions

This section should be divided into:

Implication for Policy/Management

This summarises the state of the evidence base and the extent to which this informs decision making in relation to the review question and any measure of the uncertainty surrounding the outcome. The intention is to inform and any form of advocacy should be excluded.

Implication for Research

This section summarises the shortcomings of the current evidence base in terms of knowledge gaps and the need for primary research. In this section some advocacy for research is permissible provided it is clearly justified by the review outcome. This should take the form of recommendations for future study designs that would improve the evidence base. 


All manuscripts must contain the following sections under the heading 'Declarations':

  • Ethics approval and consent to participate
  • Consent for publication
  • Availability of data and material
  • Competing interests
  • Funding
  • Authors' contributions
  • Acknowledgements
  • Authors' information (optional)

Please see below for details on the information to be included in these sections.

If any of the sections are not relevant to your manuscript, please include the heading and write 'Not applicable' for that section.

Ethics approval and consent to participate

Manuscripts reporting studies involving human participants, human data or human tissue must:

  • include a statement on ethics approval and consent (even where the need for approval was waived)
  • include the name of the ethics committee that approved the study and the committee’s reference number if appropriate

Studies involving animals must include a statement on ethics approval.

See our editorial policies for more information.

If your manuscript does not report on or involve the use of any animal or human data or tissue, please state “Not applicable” in this section.

Consent for publication

If your manuscript contains any individual person’s data in any form (including individual details, images or videos), consent for publication must be obtained from that person, or in the case of children, their parent or legal guardian. All presentations of case reports must have consent for publication.

You can use your institutional consent form or our consent form if you prefer. You should not send the form to us on submission, but we may request to see a copy at any stage (including after publication).

See our editorial policies for more information on consent for publication.

If your manuscript does not contain any data from any individual person, please state “Not applicable” in this section.

Availability of data and materials

All manuscripts must include an ‘Availability of data and materials’ statement. Data availability statements should include information on where data supporting the results reported in the article can be found including, where applicable, hyperlinks to publicly archived datasets analysed or generated during the study. By data we mean the minimal dataset that would be necessary to interpret, replicate and build upon the findings reported in the article. We recognise it is not always possible to share research data publicly, for instance when individual privacy could be compromised, and in such instances data availability should still be stated in the manuscript along with any conditions for access.

Data availability statements can take one of the following forms (or a combination of more than one if required for multiple datasets): 

  • The datasets generated and/or analysed during the current study are available in the [NAME] repository, [PERSISTENT WEB LINK TO DATASETS]
  • The datasets generated and/or analysed during the current study are available from the corresponding author on reasonable request.
  • All data generated or analysed during this study are included in this published article [and its supplementary information files].
  • The datasets generated and/or analysed during the current study are not publicly available due [REASON WHY DATA ARE NOT PUBLIC] but are available from the corresponding author on reasonable request.
  • Data sharing is not applicable to this article as no datasets were generated or analysed during the current study.
  • The data that support the findings of this study are available from [third party name] but restrictions apply to the availability of these data, which were used under license for the current study, and so are not publicly available. Data are however available from the authors upon reasonable request and with permission of [third party name].
  • Not applicable. If your manuscript does not contain any data, please state 'Not applicable' in this section.

More examples of template data availability statements, which include examples of openly available and restricted access datasets, are available here.

BioMed Central also requires that authors cite any publicly available data on which the conclusions of the paper rely in the manuscript. Data citations should include a persistent identifier (such as a DOI) and should ideally be included in the reference list. Citations of datasets, when they appear in the reference list, should include the minimum information recommended by DataCite and follow journal style. Dataset identifiers including DOIs should be expressed as full URLs. For example:

Hao Z, AghaKouchak A, Nakhjiri N, Farahmand A. Global integrated drought monitoring and prediction system (GIDMaPS) data sets. figshare. 2014.

With the corresponding text in the Availability of data and materials statement:

The datasets generated during and/or analysed during the current study are available in the [NAME] repository, [PERSISTENT WEB LINK TO DATASETS].[Reference number]

Competing interests

All financial and non-financial competing interests must be declared in this section.

See our editorial policies for a full explanation of competing interests. If you are unsure whether you or any of your co-authors have a competing interest please contact the editorial office.

Please use the authors initials to refer to each author's competing interests in this section.

If you do not have any competing interests, please state "The authors declare that they have no competing interests" in this section.


All sources of funding for the research reported should be declared. The role of the funding body in the design of the study and collection, analysis, and interpretation of data and in writing the manuscript should be declared.

Authors' contributions

The individual contributions of authors to the manuscript should be specified in this section. Guidance and criteria for authorship can be found in our editorial policies.

Please use initials to refer to each author's contribution in this section, for example: "FC analyzed and interpreted the patient data regarding the hematological disease and the transplant. RH performed the histological examination of the kidney, and was a major contributor in writing the manuscript. All authors read and approved the final manuscript."


Please acknowledge anyone who contributed towards the article who does not meet the criteria for authorship, including anyone who provided professional writing services or materials.

Authors should obtain permission to acknowledge from all those mentioned in the Acknowledgements section.

See our editorial policies for a full explanation of acknowledgements and authorship criteria.

If you do not have anyone to acknowledge, please write "Not applicable" in this section.

Group authorship (for manuscripts involving a collaboration group): if you would like the names of the individual members of a collaboration group to be searchable through their individual PubMed records, please ensure that the title of the collaboration group is included on the title page and in the submission system and also include collaborating author names as the last paragraph of the “Acknowledgements” section. Please add authors in the format First Name, Middle initial(s) (optional), Last Name. You can add institution or country information for each author if you wish, but this should be consistent across all authors.

Please note that individual names may not be present in the PubMed record at the time a published article is initially included in PubMed as it takes PubMed additional time to code this information.

Authors' information

This section is optional.

You may choose to use this section to include any relevant information about the author(s) that may aid the reader's interpretation of the article, and understand the standpoint of the author(s). This may include details about the authors' qualifications, current positions they hold at institutions or societies, or any other relevant background information. Please refer to authors using their initials. Note this section should not be used to describe any competing interests.


Endnotes should be designated within the text using a superscript lowercase letter and all notes (along with their corresponding letter) should be included in the Endnotes section. Please format this section in a paragraph rather than a list.


All references, including URLs, must be numbered consecutively, in square brackets, in the order in which they are cited in the text, followed by any in tables or legends. The reference numbers must be finalized and the reference list fully formatted before submission.

Examples of the BioMed Central reference style are shown below. Please ensure that the reference style is followed precisely.

See our editorial policies for author guidance on good citation practice.

Web links and URLs: All web links and URLs, including links to the authors' own websites, should be given a reference number and included in the reference list rather than within the text of the manuscript. They should be provided in full, including both the title of the site and the URL, as well as the date the site was accessed, in the following format: The Mouse Tumor Biology Database. Accessed 20 May 2013. If an author or group of authors can clearly be associated with a web link (e.g. for blogs) they should be included in the reference.

Example reference style:

Article within a journal
Smith JJ. The world of science. Am J Sci. 1999;36:234-5.

Article within a journal (no page numbers)
Rohrmann S, Overvad K, Bueno-de-Mesquita HB, Jakobsen MU, Egeberg R, Tjønneland A, et al. Meat consumption and mortality - results from the European Prospective Investigation into Cancer and Nutrition. BMC Med. 2013;11:63.

Article within a journal by DOI
Slifka MK, Whitton JL. Clinical implications of dysregulated cytokine production. Dig J Mol Med. 2000; doi:10.1007/s801090000086.

Article within a journal supplement
Frumin AM, Nussbaum J, Esposito M. Functional asplenia: demonstration of splenic activity by bone marrow scan. Blood 1979;59 Suppl 1:26-32.

Book chapter, or an article within a book
Wyllie AH, Kerr JFR, Currie AR. Cell death: the significance of apoptosis. In: Bourne GH, Danielli JF, Jeon KW, editors. International review of cytology. London: Academic; 1980. p. 251-306.

OnlineFirst chapter in a series (without a volume designation but with a DOI)
Saito Y, Hyuga H. Rate equation approaches to amplification of enantiomeric excess and chiral symmetry breaking. Top Curr Chem. 2007. doi:10.1007/128_2006_108.

Complete book, authored
Blenkinsopp A, Paxton P. Symptoms in the pharmacy: a guide to the management of common illness. 3rd ed. Oxford: Blackwell Science; 1998.

Online document
Doe J. Title of subordinate document. In: The dictionary of substances and their effects. Royal Society of Chemistry. 1999. of subordinate document. Accessed 15 Jan 1999.

Online database
Healthwise Knowledgebase. US Pharmacopeia, Rockville. 1998. Accessed 21 Sept 1998.

Supplementary material/private homepage
Doe J. Title of supplementary material. 2000. Accessed 22 Feb 2000.

University site
Doe, J: Title of preprint. (1999). Accessed 25 Dec 1999.

FTP site
Doe, J: Trivial HTTP, RFC2169. (1999). Accessed 12 Nov 1999.

Organization site
ISSN International Centre: The ISSN register. (2006). Accessed 20 Feb 2007.

Dataset with persistent identifier
Zheng L-Y, Guo X-S, He B, Sun L-J, Peng Y, Dong S-S, et al. Genome data from sweet and grain sorghum (Sorghum bicolor). GigaScience Database. 2011.

Figures, tables and additional files

See General formatting guidelines for information on how to format figures, tables and additional files.

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