More sophisticated databases use subject headings (aka 'descriptors', 'index terms', 'controlled vocabulary'). These are taken from a regularly updated thesaurus of terms suited to the disciplinary focus of the database.
Subject headings are applied to best represent the content of records within the database. Searching with an appropriate subject heading will help find material on that topic whatever the terminology used by the authors.
Database records and thesauri of subject headings contain terms that reflect language and attitudes of the authors and period in which publications were written. Some terms are outdated, offensive, and inappropriate. |
Examples of how to search directly for subject headings (if known) in the search box.
Database | Interface | Example subject heading |
---|---|---|
APA PsycInfo, Embase, Emcare, MEDLINE | Ovid | Health education/ |
Business Source Ultimate | EBSCOhost | DE "EDUCATION & economics" |
CINAHL Complete | EBSCOhost | MH "Health Education" |
Cochrane Library | Cochrane Library |
[mh ^"health education"] |
ERIC | ProQuest | MAINSUBJECT.EXACT("Patient Education") |
SPORTDiscus | EBSCOhost | DE "HEALTH education" |
Different databases may use different thesauri, and these vary in their depth and coverage of topics. A subject heading in one database may not be included in another, or may be defined differently. It is best practice to check each subject heading in each database. This can be done via the scope note and checking where the heading sits within the thesaurus structure.
The Medical Subject Headings thesaurus produced by the National Library of Medicine and used in MEDLINE is one of the oldest and best-known health thesauri. MeSH are used in several databases, and were used as the foundation for several other health thesauri.
MEDLINE is usually the first database you will search for your health systematic or scoping review. The MEDLINE search strategy is often used as the 'master' search strategy.
MeSH in MEDLINE (Ovid): Headings are presented in a hierarchical structure from broader to narrower. Below demonstrates where the subject heading "Health Education" fits within the MeSH structure. A plus symbol next to a heading indicates that there are more narrow headings below that heading.
Term Finder in MEDLINE: Another way to explore MeSH in MEDLINE is via the Term Finder. This short video from Wolters Kluwer explains the basics of using this feature. (Video length - 4 min 0 sec)
Emtree in Embase or Emcare (Ovid): Headings are not presented in a hierarchical structure. Can only see one level above and below the heading searched for.
Business Thesaurus in Business Source Ultimate (EBSCOhost): Headings are not presented in a hierarchical structure. Can only see one level above and below the heading searched for. Must click on narrower terms to see headings further below as no indication given when further terms exist e.g. no [ + ], [NT].
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Example: MEDLINE (Ovid) - accessing the thesaurus and Scope Note via Advanced Search or the Term Finder. Always check for relevant narrower terms, and the Scope Note for definitions, previous indexing and keywords.
Choosing to 'explode' a subject heading finds sources associated with the heading and all the narrower headings below it in the hierarchical structure of the relevant thesaurus¹. This will expand your results to include sources about the broader topic and the narrower headings.
¹Not in SPORTDiscus and Business Source Ultimate - only first level of narrower headings are searched.
When to use: Sometimes sources are indexed to specific or narrow terms, so by choosing a broad subject heading, you may not find every document that is relevant to your topic. If you have checked where a subject heading sits within the thesaurus and most or all of the narrower headings are relevant, consider exploding that subject heading.
Limitations: May return results that are not relevant to your topic. Only explode a subject heading if most or all of the narrower headings are relevant.
Example: Explode in MEDLINE (Ovid) using 'Map Term to Subject Heading': Search for your heading with the 'Map Term to Subject Heading' box ticked. On the following page, select the box left of the heading (1) and the 'Explode' box (2), then 'Continue' (3). 'Continue' again to select all subheadings and then the exploded subject heading will appear in the search history. The same format applies in other databases that use the Ovid interface e.g. APA PsycInfo, Embase and Emcare.
Example: Explode in MEDLINE (Ovid) - Direct search: Search directly for an exploded heading in the search box by entering 'exp' before the heading, and with a forward slash ( / ) preceding the heading. The same format applies in other databases that use the Ovid interface e.g. APA PsycInfo, Embase, and Emcare.
Format examples of exploded subject headings in specific databases as they appear in the search history.
Database | Interface | Example exploded subject heading |
---|---|---|
APA PsycInfo, Embase, Emcare, MEDLINE | Ovid | exp Health education/ |
Business Source Ultimate | EBSCOhost | DE "EDUCATION & economics" OR (all narrower terms from the first level below Education & economics subject heading) |
CINAHL Complete | EBSCOhost | MH "Health Education+" |
Cochrane Library | Cochrane Library |
There are two ways to do this: MeSH descriptor: [Health Education] explode all trees or [mh "Health Education"] |
ERIC | ProQuest | MAINSUBJECT.EXACT.EXPLODE("Patient Education") |
SPORTDiscus | EBSCOhost | DE "EDUCATION" OR (all narrower terms from the first level below Education subject heading) |
Choosing to 'focus' as subject heading finds only documents in which the subject heading is considered the major topic. This will narrow your results and return highly specific sources.
When to use: If your topic has a large body of existing literature, focusing a subject heading can help narrow results to only those that discuss the topic in depth.
Limitations: Can limit the number of results in a search. If you get too few results, run the search again without focusing the heading.
Example: Focus in MEDLINE (Ovid) using 'Map Term to Subject Heading': Search for you heading with the 'Map Term to Subject Heading' box ticked. On the following page, tick the box left of the heading (1) and the 'Focus' box (2), and then 'Continue' (3). 'Continue' again to select all subheadings and then the focused subject heading will appear in search history. The same format applies in other databases that use the Ovid interface e.g. APA PsycInfo, Embase, and Emcare.
Example: Focus in MEDLINE (Ovid) - Direct search: Search directly for a focused heading in the search box by entering an asterisk ( * ) before the heading, and with a forward slash ( / ) preceding the heading. The same format applies in other databases that use the Ovid interface e.g. APA PsycINFO, Embase and Emcare.
Format examples of focused subject headings in specific databases as they appear in the search history.
Database | Interface | Example focused subject heading |
---|---|---|
APA PsycInfo, Embase, Emcare, MEDLINE | Ovid | *Health education/ |
CINAHL Complete | EBSCOhost | MM "Health Education" |
Cochrane Library | Cochrane Library | [mh Education[mj]] |
ERIC | ProQuest | MJMAINSUBJECT.EXACT ("Patient Education") |
No option to focus subject headings in Business Source Ultimate, SPORTDiscus.
Qualifiers, also called subheadings, can be used in combination with subject headings to restrict the focus of your search to a particular aspect of a subject. This can improve the precision of your search.
Databases with qualifiers: CINAHL Complete, Cochrane Library, Embase, Emcare, MEDLINE
Databases without qualifiers: If you have incorporated qualifiers in your master search, you will need to remove or substitute them in the following databases: APA PsycInfo, Business Source Ultimate, ERIC, SPORTDiscus
When to use: To narrow in on a particular concept within a subject heading. For example, a MEDLINE search for 'Health Education/td' will return results that specifically include trends in health education and not other aspects of education.
Limitations: Can limit the number of results in a search. If you get too few results, you can run the search again with more or all of the qualifiers selected.
Other considerations:
Not all qualifiers can be used in conjunction with all subject headings.
Not all qualifiers were introduced into all databases at the same time.
Example: Using qualifiers in MEDLINE (Ovid) using 'Map Term to Subject Heading': Search for your heading with the 'Map Term to Subject Heading' box ticked. On the following page, tick the box left of the heading, and then 'Continue'.
The next page presents the available qualifiers for the subject heading you have chosen.
1. Clicking 'Continue' or 'Include All Subheadings' searches the subject heading with all qualifiers.
2. Tick the checkbox next to individual qualifiers to search the subject heading with one or more qualifiers.
3. Click the information icon next to a qualifier to see its definition and year of entry.
Once you have made your selection(s), click continue. The subject heading with qualifier(s) will appear in the search history. The same format applies in other databases that use the Ovid interface e.g. Embase.
Example: Using qualifiers in MEDLINE (Ovid) - Direct search: Search directly for a subject heading with qualifier(s) applied in the search box by entering the two-letter qualifier code after the term and forward slash. You can find the qualifier codes in the MeSH Qualifiers List (linked above).
Format examples of subject headings with a qualifier applied in specific databases as they appear in the search history.
Database | Interface | Example subject heading with qualifier |
CINAHL Complete | EBSCOhost | (MH “Health Education/ST”) |
Cochrane Library | Cochrane Library |
MeSH descriptor: [Health Education] explode all trees and with qualifier(s): [standards – ST] OR type directly into search: [mh “Health Education”/ST] |
Embase | Ovid | Education/rh |
MEDLINE | Ovid | Health education/st |
In some databases, qualifiers can be searched on their own (without a subject heading). These are known as floating subject headings.
Databases with floating subject headings: CINAHL, Cochrane Library, Embase, Emcare, MEDLINE
Databases without floating subject headings: If you have incorporated floating subject headings in your master search, you will need to remove or substitute them in the following databases: APA PsycInfo, Business Source Ultimate, ERIC, SPORTDiscus
When to use: When there is a particular element you are interested in that is best represented by a qualifier rather than a subject heading. For example, you may be interested in finding standards across multiple disciplines. 'Standards' is a qualifier in MEDLINE and CINAHL and can be searched as a floating subject heading. This will return results where the qualifier 'Standards' has been applied to any subject heading.
Limitations: Brings in results where the qualifier is attached to any subject heading where the pairing is possible. If this brings in lots of irrelevant sources, try combining the floating subject heading with keywords. e.g. st.fs. AND (patient educat*).
You can also use a floating subject heading search to help find additional subject headings.
It is best practice to search using both keywords and subject headings. In databases with thesauri, some records may not have headings, or be poorly indexed.
Example: MEDLINE (Ovid) - searching using both subject headings and keywords (subject headings are denoted by a forward slash / )
For more information about keyword searching, visit the Keywords page of this guide.
Many databases use a thesaurus. It's important to note which is used by the databases you search.
Database | Thesaurus |
Cochrane Library databases | Medical Subject Headings (MeSH) (select records only) |
MEDLINE | Medical Subject Headings (MeSH) |
Emcare, Embase | Emtree |
PsycInfo | Thesaurus of Psychological Index Terms |
SPORTDiscus | Sports Thesaurus |
CINAHL | CINAHL Subject Headings |
ERIC | ERIC Thesaurus |
ProQuest Dissertations and Theses, Web of Science databases, Scopus | Inconsistently applied subject headings from various thesauri may be present. Search using keywords |
When you search for a subject heading within Ovid MEDLINE, you may unknowingly include irrelevant subject headings or miss all available headings.
For example, these narrower headings appear under Nursing after running a search in Advanced Search - here Nursing falls under Health Occupations:
Nursing also appears in other parts of the thesaurus. To see all sections where Nursing appears, select Contexts at the top of the page:
You will now see additional headings under Professional Practice > Nursing:
All narrower terms, under every instance of Nursing, are included by default if you Explode the Nursing subject heading.
Alternatively, use the Term Finder - search for the heading, then click MeSH Tree under the relevant heading to see where the heading appears in all 'branches'.
The free MeSH Browser also provides a quick way to navigate the MeSH tree.