The essential feature of shared psychotic disorder (folie à deux) is a delusion that develops in an individual who is involved in a close relationship with another person (sometimes termed the “inducer” or “the primary case”) who already has a psychotic disorder with prominent delusions.
The content of the shared delusional beliefs may be dependent on the diagnosis of the primary case and can include relatively bizarre delusions (e.g., that radiation is being transmitted into an apartment from a hostile foreign power, causing indigestion and diarrhea), mood-congruent delusions (e.g., that the primary case will soon receive a film contract for $2 million, allowing the family to purchase a much larger home with a swimming pool), or the nonbizarre delusions that are characteristic of delusional disorder (e.g., the FBI is tapping the family telephone and trailing family members when they go out).
Usually the primary case in shared psychotic disorder is dominant in the relationship and gradually imposes the delusional system on the more passive and initially healthy second person. Individuals who come to share delusional beliefs are often related by blood or marriage and have lived together for a long time, sometimes in relative social isolation. If the relationship with the primary case is interrupted, the delusional beliefs of the other individual usually diminish or disappear.
Although most commonly seen in relationships of only two people, shared psychotic disorder can occur among a larger number of individuals, especially in family situations in which the parent is the primary case and the children, sometimes to varying degrees, adopt the parent’s delusional beliefs. Individuals with this disorder rarely seek treatment and usually are brought to clinical attention when the primary case receives treatment.
Specific Symptoms of Shared Psychotic Disorder
- A delusion develops in an individual in the context of a close relationship with another person(s), who has an already-established delusion.
- The delusion is similar in content to that of the person who already has the established delusion.
- The disturbance is not better accounted for by another psychotic disorder (e.g., schizophrenia) or a mood disorder with psychotic features and is not due to the direct physiological effects of a substance (e.g., a drug of abuse, a medication) or a general medical condition.