Shared psychosis occurs when individuals acquire a delusion from someone with whom they have a close personal relationship.
Psychosis refers to symptoms such as delusions, hallucinations, disorganised thinking and speech, and bizarre and inappropriate motor behaviour (including catatonia) that indicate loss of contact with reality (refer to Schizophrenia and Related Disorders).
Shared psychosis (previously termed folie à deux) is now considered a subset of delusional disorder.
It is a rare disorder that usually occurs in a person or group of people (usually a family) who are related to a person with a significant delusional disorder.
The socially dominant member in the relationship has the primary disorder and imposes the delusion on or convinces the less dominant person (or people) in the relationship of the unusual beliefs.
Medical professionals try to identify the individual in the relationship who has the primary psychosis, because the individual with the secondary disorder typically does not maintain the delusional beliefs when separated from the individual with the primary disorder.
Counselling and therapy can usually help individuals who have a shared psychosis.
Psychotic symptoms are treated with anti-psychotic drugs as needed.