MeSH is structured and cross-referenced automatically to help you find the most relevant results when searching PubMed. You can dig deeper into how MeSH terms are mapped to a particular search result by going to the Advanced Search page and viewing the "Search Details."
For example, here are the search details for our search on blood pressure:
You can see this mapping wherever the [MeSH Terms] tag appears in your Search Details. This search tag directs PubMed to search in the MeSH section of the MEDLINE record. (Note: for a complete list of PubMed search tags, see the PubMed User Guide: Search field tags.)
Notice that these are the MeSH terms that were automatically mapped in the search:
Although the search details do not show the narrower terms, these MeSH terms also "exploded" to include narrower concepts, such as:
Any citation indexed with any of these narrower terms will also be retrieved. If a term appears in multiple places in the MeSH hierarchy, all of its narrower terms will be included in a search.
You can use the Boolean operators AND, OR, and NOT to create specific searches in the query box.
While MeSH is an efficient system working in the background of MEDLINE/PubMed, it doesn’t cover everything that can be searched. Searching only within the MeSH fields can exclude some relevant results: