Nesting ConceptsYou may have noticed the use of parentheses in our previous searches. For databases like Pubmed where there is only a single search box, you may need to use parentheses in conjunction with your boolean operators (especially OR).
Take a look at this search:
Neonatal Intensive Care Unit AND Sound OR Noise
177,813 results
This search retrieved a TON of results!!! This is because it is searching for articles about Neonatal Intensive Care Unit and sound. OR... you might find articles that use the keyword sound, even if the article has nothing to do with the NICU.
To fix this, you can use parentheses to "nest" your synonyms. Just like a mathematical formula, this will tell the database to process the request inside the parentheses first.
Neonatal Intensive Care Unit AND (Sound OR Noise)
640 results
This new search will bring back every article in the database that contains the words Neonatal Intensive Care Unit and either the word sound or noise.
The other option for building a search is to use PubMed's Advanced Search Builder. This will allow you to enter each concept separately, and PubMed will automatically nest your concepts. This also allows you to search for subject headings.
Try It OutLet's use the Advanced Search Builder to search for:
ketamine AND postoperative pain AND children
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