Some databases have the option to search using database-specific subject headings, also referred to as subject terms, thesaurus terms, and indexed terms. Subject headings are a set of pre-determined terms (a controlled vocabulary) describing concepts within a specific database. In most cases, subject headings are applied to database records by human indexers who have read the full-text to understand the main subjects discussed, although some databases use automation as well.
The following page works through subject heading search options available on the Ovid platform that is used for a number of databases such as MEDLINE, Embase, PsycINFO, Cochrane Library, etc. The examples and screenshots provided are from Embase database and may function or appear slightly different on other databases available via Ovid.
(Note: searching without subject headings is referred to as keyword searching. By default, many databases search for your keyword search terms in the bibliographic details of the record i.e. the article title, abstract, author keywords, as well as in the database-specific subject headings)
For example: the terms insomnia and sleeplessness can be used to describe the same concept. The database will have a pre-determined term (subject heading) to search for records that are about the concept of insomnia / sleeplessness, regardless of what words are used to describe the concept in the bibliographic details. For the same reason, we don’t have to worry about different spellings (ex. paediatrics vs pediatrics) for the same concept when searching with subject headings
For example: searching the subject heading that the Embase database uses for the concept of insomnia, presents a list of more specific types of insomnia that you can easily choose to include or leave out (see further down the page)