Databases have unique sets of controlled vocabularies, or subject headings, to help narrow a topic and target results. Combine several subjects together, or try a subject and keyword search. Below are examples of two types of subject searches.

opens new windowMEDLINE and opens new windowCINAHL use the medical subjects in MeSH 2022. As shown in the example below for Reactive Attachment Disorder, MeSH lists subheadings, which can be marked and used to narrow search results.

Subject headings in CINAHL differ from those in MEDLINE, which includes veterinary medicine.

The psychology databases, opens new windowAPA PsycArticles and opens new windowAPA PsycInfo use a psychology thesaurus with controlled vocabularies relevant to the discipline. As shown below, terms differ from those in MEDLINE for the same subject search, reactive attachment disorder.