Health Sciences Literature Searching: Keywords and Subject Headings

Controlled vocabulary is the use of search terms specific to a database.

Let's say you want to do a search on the thing that you breathe through and sticks out of your face. Normally, you'd say “nose”. But there are different ways to say "nose", like “schnoz” or “sniffer.” Although we know that “sniffer” means the same thing as “nose”, it is not a professional way of saying it. 

Health Sciences professionals are more likely to say "sinuses" or "nasal passages" more than "sniffer", so it is wiser to use the term "sinuses" in a health literature search.

CINAHL and PubMed have these terms built in so that you don't have to guess what a professional author would use as his description. Click on the links to see how you can use this subject headings to narrow your search by database.

For a comprehensive search, always search both subject headings and keywords for each concept.

Keyword searching means using terms you choose yourself to search on a database. 

Subject heading searching means using a "controlled vocabulary" to search for articles tagged with that term. Each database uses its own subject headings.

EXAMPLE:

Sometimes subject headings and keywords are the same, but often they aren't. The CINAHL Subject Heading for Self-Help Groups is Support Groups. Using only the keyword "Self-Help Groups" will leave out some articles tagged with the subject heading, but using only the subject heading will leave out some articles that use the keyword.

Why use Subject Headings (aka as Controlled Vocabulary)?

Subject Databases use "controlled vocabularies" made up of subject headings, organized hierarchically. Subject headings solve 2 major problems we encounter when relying solely on keyword searching: Synonyms and Ambiguity. 

Synonyms:

Pet Therapy = animal assisted therapy, therapy dog, therapy dogs, equine-assisted therapy, therapy animals, etc. 

If you only searched for 'pet therapy', you'd miss all articles that use 'therapy dog' to describe that concept. It's very difficult to think of all the potential ways of expressing a concept. 

Ambiguity: 

Pet therapy = animal assisted therapy, Positron emission tomography

If you searched for 'pet therapy', thinking you'd retrieve only articles about therapy animals, you'd have to sift through quite a bit of literature on PET imaging. 

So, to solve these problems, you could search the subject heading for the concept of pet therapy. In Pubmed, the Mesh is Animal Assisted Therapy. In CINAHL, it's Pet Therapy. 

Different Subject Databases use Different Controlled Vocabularies

Search strategies MUST be customized for each database:

• databases use different subject headings to describe the same concept
• a database can't be searched effectively unless the correct subject headings are used
• each database requires it's own, unique search strategy