What is the correct way to search in PubMed using Boolean operators?
Most PubMed searches do not require Boolean operators to be in uppercase characters. The system recognizes both Boolean OR and NOT in either lower or uppercase. However, lowercase Boolean AND is processed as a stopword rather than a Boolean operator because it is sometimes embedded in MeSH Terms and Subheadings. When you search with a lowercase Boolean AND, click the Details tab to see how the search is translated, e.g., breast cancer and therapy is translated so that and becomes AND. Processing lowercase and as a stopword works well for most PubMed queries that simply include search terms; however queries that include search tags or search history numbers may require an uppercase AND. See the two examples that include a search tag below: For example: breast cancer AND therapy[sh] successfully translates to: ((“breast neoplasms”[TIAB] NOT Medline[SB]) OR “breast neoplasms”[MeSH Terms] OR breast cancer[Text Word]) AND “therapy”[Subheading] breast cancer and therapy[sh] fails to translat
