Folie à deux or induced psychotic disorder is a rare psychiatric illness and was first described in the 19th century. The essential feature is a psychotic disorder shared by two emotionally close persons, usually a blood relative or spouse, while living in relative isolation. The disorder is characterized by a primary psychotic person, usually older, more intelligent and better educated who gradually imposes her delusional beliefs on the other person, who is often dependent on or submissive to the person with the psychotic disorder. The disorder usually resolves in the more passive person when the two are separated.

To describe two case studies of two couples who shared psychotic illness and make a review of the literature.

Search in the PubMed/MedLine and Medscape databases with the following key words: folie à deux; shared psychosis; shared delusion.

Even though Folie a deux is rare to diagnose, clinicians should be aware of this condition, since it is tremendously important to treat properly both people involved.