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Guide to searching PubMed

Boolean Operators

Boolean Operators

Used to connect terms.

Tells the database that you only want articles containing BOTH of the search terms

Tells the database that you want all articles containing EITHER of the terms (this one or that one).

Tells the database to exclude a certain term.

(Smoking OR Nicotine) AND cancer
Tells the database that you want articles with EITHER of two terms AND another.  

Nesting (parenthesis) synonyms ensures that the search is executed properly.  OR terms are done first, then AND'd with cancer.


Databases usually allow you to limit or filter your search results in various ways. These may include:

  • Language
  • Type of publication (case study, clinical trials, review articles)
  • Sex
  • Age groups
  • Date published
  • Peer-reviewed


PubMed uses * for truncation.  Truncating the "root" of your word allows you to pull in variant endings of the word.

Truncation is generally not recommended in PubMed.  Truncation bypasses Automatic Term Mapping and automatic explosion.  Also, in such a large database, variations of a text string can become overwhelming and unmanageable.  

Sometimes, however, truncation can be useful.  Use it with care.



 Use with root of word.

 Turns off term mapping.

 Turns off explosions



 Pharmacology, pharmacy, etc. 

 Injured, injury, injuries, etc.

Exact Phrase

Use quotation marks around words that generally appear side by side to search for an "exact phrase".

For example, "Roles Maudsley Score"

Finds information on the Roles Maudsley Score, exactly like this, with those words glued together.  Just searching these words typed in side by side without " " would find records that contain the word Roles or Maudsley somewhere in the record, and score somewhere else in the record.  

Use exact phrases with care, particularly with test names.    

For example, using the above test as an exact phrase would've missed finding the following information, because Roles Maudsley Score goes by several name variations:  Roles and Maudsley, Maudsley Scale, Maudsley Classification, Roles and Maudsley Score, or Roles and Maudsley Scoring System.