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Systematic Reviews: Medical Subject Headings (MeSH)

Overview of systematic review methodology and key strategies for searching and reporting to the Cochrane Collaboration's Gold Standard

Heading: Medical subject headings (Mesh)

Medical Subject Headings (MeSH) overview

It is best practice to search using both keywords and subject headings.

Move through the slide deck below to learn how to use Medical Subject Headings (MeSH) in your search. Alternatively, download the PDF document at the bottom of this box.

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Subject searching

Subject headings allow you to find all articles about a particular concept. They use a controlled vocabulary to group together all articles on a similar topic. Many medical databases have a subject thesaurus which you should use when searching. 

For example, MEDLINE articles about meningitis that is caused by any sort of bacteria have the subject heading Meningitis, Bacterial/.

Screenshot of MeSH tree showing subject heading Meningitis, and the nested subheadings.

Rules to remember

1. For each of your concepts, search using both subject headings and keywords.

2. Start your search in MEDLINE and use the MeSH because MeSH is very comprehensive.

3. Always check a subject's scope, e.g. look at the scope note (select the Scope icon). Does it match what you want?

Screenshot of MEDLINE search page, showing the selection of the subject heading meningitis

4. Always search one database and one concept at a time.

5. If you use a subject heading also run it as a keyword search (see below).

Note the subject heading has a forward slash e.g. Meningitis, Bacterial/

Screenshot of MEDLINE search history, showing how to connect subject heading and keyword lines by ticking the check boxes and selecting or.

Database thesauri

Many databases use a controlled vocabulary, such as Medical Subject Headings (MeSH), or create their own.

It is important to note which controlled vocabulary is used by the database you choose.

Database Controlled vocabulary used
Cochrane Medical Subject Headings (MeSH)
MEDLINE Medical Subject Headings (MeSH)
Emcare Emtree thesaurus
Embase Emtree thesaurus
PsycINFO Thesaurus of Psychological Index Terms

Caution - 'hidden' subject headings in Ovid MEDLINE

When you search for a subject heading within Ovid MEDLINE, you may be unknowingly including irrelevant subject headings or missing all the available headings.

How this is the case - example:

You will see four subject headings underneath the subject heading Nursing after running a search for it - in this case, Nursing falls under the broad branch of Disciplines and Occupations:

Screenshot of MEDLINE search page, showing the selection of the subject headings under Nursing after initial search

However, Nursing also appears in other parts of the thesaurus. To find each section of the thesaurus where Nursing appears, you need to select Contexts at the top of the page next to Continue:

Screenshot of MEDLINE search page, showing how to select Contexts

After selecting Contexts, in addition to the four headings obtained before, you will now see an additional five headings under Professional Practice:

Screenshot of MEDLINE search page, showing the selection of the subject headings under Nursing after selecting Contexts

An easy way to see where a term appears in the thesaurus is by using the Ovid Term Finder when searching Ovid MEDLINE - search for the heading, and then click MeSH Tree under the relevant heading to see all 'branches'.

Alternatively you can use the free MeSH browser while you are searching Ovid (however the scope notes may be less detailed).

It is important to note that all narrower terms, under every instance of Nursing are included by default when you Explode the Nursing subject heading even though they did not appear when you searched for it earlier.