Once you have your PICO(T) terms, you will need to enter them into whatever database or search engine you are using. Within databases, you have the option of using keywords or subject headings for the different parts of your PICO(T).
Each database has its own set of subject headings, designed specifically for the literature from the field(s) of study the database contains. Knowing the difference between keywords and subject headings, as well as the advantages and disadvantages for both of them, can help you perform better searches.
The chart below shows some examples of keywords and the equivalent subject headings in CINAHL and MEDLINE
Note that the Subject Headings in CINAHL and MEDLINE are not always the same. In the last example--LGBT--note that while CINAHL has a subject heading for the term, MEDLINE requires that two different subject headings have to be combined to create an equivalent. For more information on how to combine related MeSH terms, see the next page.
Subject Headings are:
The simple answer to the question of whether you should use keywords or subject headings is: it depends. Some basic guidelines are: