Controlled vocabularies, also known as subject headings, can be thought of as a database’s thesaurus. A hierarchically organized collection of words or phrases used to describe content of a database in a consistent fashion. To learn more about what controlled vocabularies are, first read the article, “Controlled vocabulary in databases”.
Like MeSH (in PubMed), Emtree (in Embase), and CINAHL Subject Headings (in CINAHL) controlled vocabularies are useful beyond the application in their respective databases. The records for terms within these controlled vocabularies can be used to explore a topic of interest by:
- Succinctly describing a concept
- Providing synonyms
- Supplying related terms
- Disclosing the term’s indexing history
- Suggesting relevant subheadings
- Linking these concepts into coherent categories or a logical order
Below you'll find a description of the common elements that make up a subject heading record in controlled vocabularies. In addition, each element will include examples of the subject heading's application in its respective database, including: MeSH terms (in PubMed), Emtree terms (in Embase), and CINAHL Subject Headings (in CINAHL).
The subject headings
A subject heading is the preferred term for the concept searched within a controlled vocabulary. Adding subject headings to your search accounts for variations in how this concept can be described in publications and will help you discover more records on the same topic.
MeSH (PubMed)
In the record of a MeSH subject heading, select “add to search builder” to see how to format the subject heading for a search in PubMed.
For example:
- “athletic performance”[MeSH]
When you search for a phrase (with quotation marks), PubMed will not perform automatic term mappingto include MeSH terms and it’s narrower terms in the MeSH hierarchy.
For example:
- If you search “athletic performance”, PubMed will search for this phrase in all fields (including title, abstract, author, date, etc.) but will not automatically map to find the relevant a MeSH term.
- A search for athletic performance (without quotation marks) is translated to the following PubMed syntax: "athletic performance"[MeSH] OR ("athletic" AND "performance") OR "athletic performance" Note how the database maps to find the MeSH term, but also searches for both the words athletic and performance independently and as a phrase.
- To get results showing athletic performance as one phrase and also include the MeSH term, search "athletic performance"[MeSH] OR "athletic performance"
Emtree (Embase)
In an Emtree record of a relevant subject heading select “+Add to query builder” in the left column to format how to search that subject heading in Embase.
For example:
- ‘athletic performance’/de
Embase automatically matches a search term to the corresponding Emtree term, and will search for this term in all indexing fields (author, journal title, keywords, publication type, etc.) If you want to limit the search to specific index fields, refer to Embase’s mapping options.
CINAHL Subject Headings
Check the box next to a CINAHL Subject Heading, and select “Search Database” to format how to search with that subject heading in CINAHL.
For example:
- (MH “Athletic Performance”)
A search in CINAHL will automatically map to any relevant controlled vocabulary terms or phrases. To turn of automatic term mapping, deselect “Apply equivalent subjects” in the advance search options.
Definitions
The definition describes the concepts, like you would find in a dictionary. This definition should be reviewed for applicability to your topic.
Hierarchy
Controlled vocabularies link concepts together in a tree structure, nesting broader and narrower terms. A single concept can be nested in one or multiple tree structures; exploring these trees can indicate the broader context(s) a term sits within. The hierarchy can possibly indicate narrower or a more targeted term for your topic of interest.
In most databases searching with a subject heading will automatically ‘explode’ to also capture the term(s) nested below the subject heading used. Therefore, understanding the hierarchy can inform your decision to either adjust the search term selected (if needed) or to adjust the search mechanics to stop the explosion of terms.
MeSH (PubMed)
In PubMed a search with the subject heading, “Athletic Performance”[MeSH], will also capture the terms, cardiorespiratory fitness, physical endurance, physical fitness, and cardiorespiratory fitness.
To stop the explosion, instead search: "Athletic Performance"[Mesh:NoExp]
Emtree (Embase)
In the record of an Emtree term, select the drop-down option labeled “Extend the search using:” and select how you’d like to search with the subject heading in Embase, such as exploding the search to capture narrower terms. Then, selecting “add to query builder” will generate the syntax to use in Embase.
For example, in Embase, searching ‘athletic performance’/de will not automatically explode results. Instead, the tag /exp must be selected. The search would be: 'athletic performance'/exp
CINAHL Subject Headings
Starting from the record of a CINAHL subject heading you’d like to use, you can select the box if you’d like to explode your search to capture narrower terms. By selecting “search database”, you can see in the search bar the syntax used to search in CINAHL.
For example, (MH “Sports+”) would explode to capture narrower terms such as bodybuilding, cycling, golf, etc.
Synonyms
In a subject heading record, you’ll find a section of synonyms, these sections can also be called ‘entry terms’ or ‘used for’. These terms are not subject headings, but may highlight other ways to describe your concept, both in natural language and language used in the literature.
MeSH (PubMed)
In the MeSH record, the synonyms are under the section called entry terms. In the MeSH record for athletic performance, an example of an entry term is “Sports performance”.
Emtree (Embase)
Emtree records have a synonyms section. In the Emtree record for athletic performance, an example synonym is “Sport Performance”.
Emtree has over 370,000 Synonyms, 200,000 of which are Drug synonyms. Consider prioritizing the exploration of Emtree when researching drugs, medical devices, and chemical names.
CINAHL Subject Headings
A CINAHL Subject heading record displays synonyms under the section called used for. In the record for the CINAHL subject heading athletic performance, an example synonym is “sports performance”.
Related Terms
Sometimes called a “See Also” section of a subject heading record, related terms can connect you with other subject headings related to this concept. Explore these subject heading records and their hierarchy to gauge their applicability to your topic of interest.
MeSH (PubMed)
In the MeSH record, the related subject headings are under the section called “See Also”. In the MeSH record for athletic performance, Psychomotor Performance is a related term.
Emtree (Embase)
Emtree records do not have a related terms section.
CINAHL Subject Headings
A CINAHL Subject heading record displays synonyms under the section called Related Headings. In the record for the CINAHL subject heading athletic performance, an example of a related heading is postactivation potentiation.
Previous Indexing
As language usage changes overtime and new preferred terms are selected for a concept, the previous indexing section will disclose the prior term and the years it was in use. If you’re looking for articles published during these years, including these prior subject headings will help capture relevant literature.
MeSH (PubMed)
In the MeSH record there is a previous indexing section. In the MeSH record for athletic performance, it indicates that the subject heading for this concept used to be “Sports” from 1964 to 2007.
Emtree (Embase)
Emtree records will indicate what year the subject heading was introduced. In the Emtree record for athletic performance, it indicates that the term was introduced in 2009. Changes are made periodically, and details can be found in the Embase Release Notes.
CINAHL Subject Headings
A CINAHL Subject heading record displays previous indexing under the section called History Notes. In the record for the CINAHL subject heading “athletic performance”, it indicates the term physical performance was used before 2009.
Subheadings
Subheadings will help to describe a specific aspect of the topic. The controlled vocabulary record displays the applicable subheadings that can be applied to a term, and searching with the subheadings will narrow results based on the subheading.
MeSH (PubMed)
In the MeSH record, you can select the applicable subheading, and then select Add to Search Builder, to generate the proper syntax to search PubMed.
For example, if you were interested in the history of athletic performance you’d search, "Athletic Performance/history"[Mesh]
Emtree (Embase)
Subheadings are searched with the tag :Ink, and are available for subject headings of drug terms, medical devices, and chemical names. The list of subheadings can be found in the Embase Support Center Resources article, What are subheadings.
For example, if you are interested in the side effect of a drug, you would add the following to your search:
'side effect':lnk
CINAHL Subject Headings
In a CINAHL Subject heading record, you can select the applicable subheading and then press the “Search Database” button to generate the proper syntax.
For example, if you were interested in evaluation of athletic performance, you’d search (MH "Athletic Performance/ST/EV")
For more information on these controlled vocabularies, check out the following tutorials: