Selecting multiple topics within a domain will return the union of articles.To include all articles regardless of domain (e.g., Study design, Topics, Conditions), simply leave blank all checkboxes in the domain. Leaving blank every checkbox on the page will return all articles in the database.
For example, under Psychiatric, selecting "Mood Disorders" alone generates 14 articles; however, selecting only "PTSD" generates 52. Selecting both will list all 56 articles that pertain to Mood Disorders and/or PTSD.
Selecting multiple topics across domains will generate the intersection of articles.
For example, selecting "Persian Gulf/Gulf War" generates 18 citations, while selecting "Environmental and occupational exposures, post-deployment health" generates 72 citations. Selecting both topics generates only 15 citations because the definition has been narrowed.