Folie à deux.

A review of folie à deux or induced psychotic disorder (DSM-III-R) is provided. The author believes it to be a more frequent phenomenon than usually thought, especially when hospitalized patients are evaluated with their families. An argument is made for viewing it as a description of a relationship and possible influence between individuals who may have very different disease processes. This includes, in the secondary partner, a continuum from being very "impressionable" to having an autonomous and independent delusional disorder. A case report and suggestions for treatment are given.