Boolean operators are a way to construct a computer searchable question. Use Boolean operators (AND, OR, NOT) to combine or exclude search terms.
AND → Narrows search results
NOT → Narrows search results by excluding unwanted terms
"Quotes" → Narrows search to an exact phrase
Proximity N# → Narrows search by making sure two or more words occur within a certain number of words from each other (useful in EBSCO databases, but not available in Pubmed)
OR → Broadens search results
Truncation* → Broadens search to include various endings and spellings of a word
For example, let's say you are searching for information about spinal manipulation and exercise to treat lumbar pain.
If you want research that compares spinal manipulation and exercise, you want to connect your search terms with AND: lumbar pain AND spinal manipulation AND exercise. Using AND will retrieve all three search terms, which is important if you are looking for research that compares those treatment options.
If you want research on either spinal manipulation or exercise, you can use an OR: lumbar pain AND (spinal manipulation OR exercise). You might do this if you aren't comparing the two treatment options; rather, you want studies that include either of those types of treatment.
NOTE that I put parentheses around spinal manipulation and exercise. This is because databases read your search from left to right, like a mathematical formula. If you don't include the parenthesis, you might find information about lumbar pain and spinal manipulation... or you might just find information about exercise that has nothing to do with back pain!!
A good way to think about this is: What are your MUST-HAVE concepts? For this question, there are three: the problem (lumbar pain) and your two treatment options that you are comparing. You'll want to connect each MUST-HAVE concept with an AND. You can add alternative keywords to your search, but just make sure you are clumping together your concepts using parentheses. For example:
For this next example, you have only TWO concepts: the problem (lumbar pain) and the intervention (either exercise or spinal manipulation). You are not wanting to compare the two treatment options, but just see information about either of them -- in this case, you would nest those treatment options together with the boolean operator OR. Adding alternative keywords might look like this:
(lumbar pain OR low back pain) AND (exercise OR spinal manipulation OR "manual therapy" OR chiropractic)