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Systematic Search for Systematic Review

This guide aims to provide advice and resources for doing a systematic review.

Databases and Journals in Nursing and Health Science

Systematic review (SR) is a review of evidence-based studies and it aims to support the clinicians or researchers to find out the best available evidence to a specific problem. SR is usually conducted in the area of nursing and healthcare.

SR requires an exhaustive and systematic search of literature to ensure that all relevant evidence is included. A very important step for a systematic search is to select the databases you want to search within. Note that the databases you select and the search strategies should be described in your review as well. 

For reviews in nursing and health science areas, here is a list of core databases to start from.

     Medline is also accessible on its own via other platforms:

You may also consider including the following databases depending on your research topic.

See all available databases by subject:

Grey literature "is often used to refer to reports published outside of traditional commercial publishing." (Cochrane Handbook for Systematic Review of Interventions, chapter 4). Examples of grey literature include:

  • conference abstracts, presentations, proceedings;
  • regulatory data;
  • unpublished trial data;
  • government publications;
  • reports (such as white papers, working papers, internal documentation);
  • dissertations/theses;
  • patents; and
  • policies & procedures etc.

Searching the grey literature is important, because not all evidence is (commercially) published in journal articles delivered by major databases. It is worth noting that the producing bodies of grey literature are essential sources of quality information beyond the control of commercial publishers, as 'publishing' is normally not the primary activity of those bodies.


Theses & dissertations:


Clinical trials: 

(Learn more about clinical trials from the


Online Resources for Grey Literature discoveries in the health sector:

  • MedNar: a free, medical-focused deep web search engine.
  • OpenGrey: a multidisciplinary European database covering science, technology, biomedical science, economics, social science and humanities. Records are in English.
  • Grey Matters: a practical tool for searching health-related grey literature : provided by Canadian Agency for Drugs and Technologies (CADTH), is a checklist pointing users to a rich list of online resources to locate medical grey literature, and to record findings from each source.
  • Global Index Medicus (GIM): collated and aggregated by WHO Regional Office Libraries, provides worldwide access to biomedical and public health literature produced by and within low-middle income countries. 
  • WHO Library Database: provides access to knowledge, including governing documents, reports and technical documentation, from WHO as well as from other sources of scientific literature produced around the world.
  • NY Academy of Medicine Grey Literature Report (ceased to update from 2017): This is a searchable collection of reports compiled by The New York Academy of Medicine (NYAM) alerting readers to new grey literature publications in health services research and selected public health topics.
  • "... enables anyone with internet access to launch a single-query search of national scientific databases and portals in more than 70 countries, covering all of the world's inhabited continents and over three-quarters of the world's population. …. It provides simultaneous access to "deep web" scientific databases, which are typically not searchable by commercial search engines.” ~abstracted rom Wikipedia at

Some evidence-based journals may not be indexed in core databases you usually search in. These journals may also contain valuable works that can contribute to your systematic review. Consider to cover these journals also in your searching process.

Coverage of Databases

Different databases have different coverage in journal titles. It is worthwhile to examine the coverage of databases you selected, because this determines your search results and will have a direct impact on your review. Here is an overview of the differences in coverage across the core databases. 

Title Coverage:  Medline vs. CINAHL Complete vs. Embase vs. Cochrane Library vs. PsycINFO

[Figure 1]
  • To do a systematic review in nursing and health science fields, Medline, CINAHL (Complete), Embase and Cochrance Library are the core databases for literature searching.
  • If your research topic involves psychological problems (e.g., cognitive behavior), include PsycINFO and Web of Science (SSCI) too in your literature search.
  • Databases may have overlaps in content, and each database also covers some exclusive (unique) titles. Figure 1 illustrates the title coverage across these five databases.

Note that:

  • PubMed covers all records from Medline, plus a few other materials (about ~15%).
  • Embase includes almost all of Medline journals, while more than 2,900 journals in Embase are not covered by Medline.
  • Medline has a better coverage of US journals, while Embase has a better coverage of European journals.
  • Medline has around 1/3 (~1,800 journals) overlapped with CINAHL Complete.
  • PsycINFO has around 1/2 (~1,200) unique journals that are NOT covered by Medline, Embase and CINAHL Complete.
  • Cochrane Library includes 6 databases: 
    • Cochrane Database of Systematic Reviews (CDSR) is fully indexed by Medline
    • Cochrane Central Register of Controlled Trials (CENTRAL) contains nearly 530,000 citations, of which 310,000 (~58%) are from Medline, 50,000 (~10%) are from Embase, and the remaining 170,000 (~32%) are from other sources (Cochrane Handbook, 2011). CENTRAL covers all Randomized Controlled Trials (RCTs) and Controlled Clinical Trials (CCTs) indexed in Medline (Source).

Title Coverage:  Medline vs. CINAHL Complete vs. Embase vs. Cochrane Library vs. PsycINFO 
vs. Web of Science vs. Scopus

Web of Science and Scopus are two large multidisciplinary citation databases. You may not need to include these two databases for a systematic review, but it's good to know to what extend the core databases are covered in these two. Figure 2 gives you some indications about the title coverage.

Note that:

  • There are still many journals outside the "core collection" of databases in nursing and health science. You may also need to do hand searching in selected journals to make sure your literature search is exhausted.
  • Web of Science (SSCI) has over 2400 titles in Social Science area and around 70% of these titles are NOT covered by Medline, CINAHL Complete, Embase and PsycINFO. So if your research topic is in social science field, it's necessary to include Web of Science SSCI in your search.
  • Web of Science (SSCI) has around 660 titles in Psychiatry and Psychology areas. Around 50 titles are NOT covered by PsycINFO. So if your research topic is concerning psychology issues, do include Web of Science (SSCI) in your search.
  • Scopus covers (almost) all titles in Medline, PsycINFO and Web of Science. So most of the cases, it's not necessary to search in Scopus for your systematic review. CINAHL Complete has approx. 2000 titles that are NOT covered by Scopus. Out of these titles, more than half are magazines, trade publications, etc. 


[Figure 2]

A Comparison of Medline (via PubMed), Embase, CINAHL Complete and PsycINFO:
Medline (via PubMed) Embase CINAHL Complete (via Ebscohost) PsycINFO
(via ProQuest)
Field Biomedical Biomedical Nursing & allied health Psychological
Major subjects covered
  • Medicine
  • Nursing
  • Allied Health

Subjects in Medline

  • Drug & Pharmacy
  • Nursing
  • Allied Health
  • Biomedicine
  • OT, PT, Rehabilitation
  • Psychological literature
Year covered Since 1946 Since 1937 Since 1937 Since 1806
Number of titles

Over 5,200

  • the majority are journals
  • a small number of newspapers, magazines, etc.

Almost 8,300 journals

  • plus over
    7,700 conference proceedings

Almost 5,500

  • around 4,000 journals
  • around 1,300 magazines
  • a small number of trade publications, government documents, etc.

Over 3,000

  • over 2,500 journals; 
    99% are peer-reviewed
  • plus chapters, books, reports, theses and dissertations, etc.
Number of records Over 25 million Over 32 million Over 6 million Over 4.5 million
Descriptor (Subject Heading) MeSH Emtree (see here a
comparison of Emtree and MeSH)
CINAHL headings or MeSH Thesaurus of Psychological Index Terms

Here are some sources and references you can refer to if you need additional information.



The Venn diagrams are generated by Venn Diagram Maker Online, based on data extracted from the title lists given above (data accurate as of Dec 2016).