Frameworks like PICO can help you to identify keywords to use in a PubMed search. You shouldn’t use the entire clinical question as your search terms. Instead, you want to pull out the most important and defining words to optimize your search results. Searching using terms from regular spoken language is called a "natural language search."
Example: What is the effectiveness of St. John’s Wort compared to SSRIs in the treatment of depression in adults?
Search Terms: St. Johns Wort, SSRIs, Depression, Adults, Treatment
Truncation, also known as stemming, uses a symbol to find singular and plural forms of a word along with ending variations. Many databases use an asterisk (*) as a the symbol for truncation but it may vary by resource. (Note: Not recommended for general PubMed searches.)
Search Term: analyz* (variations of analyze)
Results: analyze, analyzes, analyzed, analyzing, analyzer, analyzation
Wildcard uses a symbol to represent a letter or set of letters in a search term. It is often used to denote spelling variations of words. Symbols for a wildcard can vary by resource, but many use a question mark (?), asterisk(*), or pound/hatch symbol (#). (Note: Not recommended for general Pubmed searches.)
Search Term: behavio?r
Results: behavior, behaviour
Note: Symbols for truncation and wildcards can vary by resource and by the number of letters they represent. While an asterisk is generally used to represent a letter or possible plural within a term, please consult your resource to determine the correct symbols.
Subject Headings are a controlled vocabulary of terms that is used by a resource, mainly databases, to describe an article. Many times, subject headings can be accessed while searching a database. Users can often find the "Suggest Subject Heading" or "Map Term to Subject Heading" option within the advanced search area of databases.
MeSH (short for Medical Subject Headings) is the National Library of Medicine’s controlled vocabulary thesaurus used for indexing articles. The database can automatically map your natural language term to a controlled MeSH term. For example, if you type in “St. Johns Wort,” the term “Hypericum” will come up. Many synonymous entry terms are mapped to the one overarching Medical Subject Heading.
MeSH Terms: Hypericum, Serotonin Uptake Inhibitors, Depressive Disorder
Other possible MeSH Terms: Phytotherapy, Mood Disorders, Antidepressive Agents, Depression
PubMed provides access to their subject heading search, MeSH Database, from the home page.
To learn more about MeSH terms and searching, the National Library of Medicine has a guided tutorial:
Medical Subject Headings (MeSH) in MEDLINE/PubMed: A Tutorial
