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Systematic Review

Being systematic

Searching literature systematically is useful for all types of literature reviews!

However, if you are writing a systematic literature review the search needs to be particularly well planned and structured to ensure it is:

  • comprehensive
  • transparent
  • replicable

These help ensure bias is eliminated and the review is methodologically sound.

To achieve the above goals, you will need to:

  • create a search strategy and ensure it is reviewed by your research group
  • document each stage of your literature searching
  • report each stage of quality appraisal 

Search terms

Identify the key concepts in your research question

The first step in developing your search strategy is identifying the key concepts your research question covers.

  • A preliminary search is often done to understand the topic and to refine your research question. 

Identify search terms

Use an iterative process to identify useful search terms for conducting your search. 

  • Brainstorm keywords and phrases that can describe each concept you have identified in your research question.
  • Create a table to record these keywords
  • Select your keywords carefully
  • Check against inclusion/exclusion criteria
  • Repeated testing is required to create a robust search strategy for a systematic review
  • Run your search on your primary database and evaluate the first page of records to see how suitable your search is
  • Identify reasons for irrelevant results and adjust your keywords accordingly 
  • Consider whether it would be useful to use broader or narrower terms for your concepts
  • Identify keywords in relevant results that you could add to your search to retrieve more relevant resources

Using a concept map or a mind map may help you clarify concepts and the relationships between or within concepts. Watch these YouTube videos for some ideas: 

Example keywords table:

Research question:
What is the relationship between adverse childhood experiences and depression in mothers during the perinatal period? 

Concept 1

adverse childhood experiences



Concept 2

perinatal depression



Concept 3


OR ACE OR postpartum depression    OR women                          
OR childhood trauma                 OR postnatal depression  
  OR maternal mental health   
    OR maternal psychological distress  

Revise your strategy/search terms until:

  • the results match your research question
  • you are confident you will find all the relevant literature on your topic

See Creating search strings for information on how to enter your search terms into databases. 

Example search string (using Scopus's Advanced search option) for the terms in the above table:

(TITLE-ABS-KEY("advserse childhood experienc*" OR ACE OR "childhood trauma") AND TITLE-ABS-KEY("perinatal depress*" OR "postpartum depress*" OR "postnatal depress*" OR "maternal mental health" OR "maternal psychological distress") AND TITLE-ABS-KEY(mother* OR women*))

See Subject headings for information on including these database specific terms to your search terms.

Choosing databases

Systematic reviewers usually use several databases to search for literature. This ensures that the searching is comprehensive and biases are minimised. 

Use both subject-specific and multidisciplinary databases to find resources relevant to your research question:

  • Subject-specific databases: in-depth coverage of literature specific to a research field.
  • Multi-disciplinary databases: literature from many research fields - help you find resources from disciplines you may not have considered.

Check for databases in your subject area via the Databases tab > Find by subject on the library homepage.

Find the key databases that are often used for systematic reviews in this guide. 

Test searches to determine database usefulness. You can consult your Liaison Librarians to finalise the list of databases for your review.



For all systematic reviews we recommend using Scopus, a high-quality, multidisciplinary database:


  • Scopus is an abstract and citation database with links to full text on publisher websites or in other databases.
  • Scopus indexes a curated collection of high quality journals along with books and conference proceedings.
  • Research outputs are across a range of fields - science, technology, medicine, social science, arts and humanities.

For systematic reviews within the health/biomedical field, we recommend including Medline as one of the databases for your review:

MEDLINE (via Ebsco, via Ovid, via PubMed)

  • Medline is the National Library of Medicine’s (NLM) article citation database.
  • Medline is hosted individually on a variety of platforms (EBSCO, OVID) and comprises the majority of PubMed.
  • Articles in Medline are indexed using MeSH headings. See Subject headings for more information on MeSH.

Note: PubMed contains all of Medline and additional citations, e.g. books, manuscripts, citations that predate Medline.

Finding additional resources

To ensure your search is comprehensive you may need to search beyond academic databases when conducting a systematic review, particularly to find grey literature (literature not published commercially and outside traditional academic sources such as journals).

Google Scholar

Google Scholar contains academic resources across disciplines and sources types. These come from academic publishers, professional societies, online repositories, universities and web sites.

Use Google Scholar

  • as an additional tool to locate relevant publications not included in high-level academic databases
  • for finding grey literature such as postgraduate theses and conference proceedings

You can limit your search to the type of websites by using; site:edu

Note that Google Scholar searches are not as replicable or transparent as academic database searches, and may find large numbers of results.

Other sources of grey literature

Watch our Finding grey literature video (3.49 mins) online.