National Institute of Mental Health sponsors a subject directory that is keyword searchable. Click on the link, National Institute of Mental Health . In the search box provided, type the word, depression and click on the search button. A search engine is a software program that goes out on the web, seeking web sites and cataloging them. A search engine constantly visits sites on the web to create a catalog of web pages and keeps them current.
Many search engines support the use of Boolean logic.
Hotbot is one search engine that supports the use of Boolean logic. In this next example, we are looking for information on the hormone, depression which is resistant to treatment . We want to find records that combine all three terms, depression and resistant and treatment . In this diagram, the resulting list are those records falling into the yellow intersection of the 3 circles. Every time you add another search term, and another AND, your result list will be smaller.