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Evidence Synthesis : Boolean Searching

Useful resources and tools for planning and conducting systematic reviews

Boolean Searching

Nearly all databases/search engines include Boolean Operators. Understanding how they work is crucial to being an efficient searcher. 

AND:

  • Narrows your search by combining two or more search terms.
  • Example: Hypertension AND "DASH Diet" 
    • would retrieve articles about how the DASH diet can help to mitigate hypertension. 

OR: 

  • Broadens your search by looking for either term. 
  • Example: (Hypertension OR "high blood pressure") AND "DASH DIET" 
    • ​​​​​​​would retrieve articles about how the DASH diet can help to mitigate hypertension OR high blood pressure. 

NOT: 

  • Narrows your search by specifically filtering out one (or more) search term
  • Example: (Hypertension OR "high blood pressure") AND "DASH DIET" NOT diabetes 
    • ​​​​​​​would retrieve articles about how the DASH diet can help to mitigate hypertension OR high blood pressure (while ignoring articles that also mention diabetes).