Diagnosing Shared Psychotic Disorder

A psychotic disorder is a mental illness that causes abnormal thinking and perceptions. Psychotic illnesses affect the person's ability to think clearly, make good judgments, respond emotionally, communicate effectively, understand reality and believe appropriately. Persons with a psychotic illness cannot stay in touch with reality and they are most often unable to meet the ordinary demands of daily life.

The symptoms of psychotic disorders include hallucinations, delusions, disorganized speech, disorganized behavior, slowed or bizarre movements, loss of interest in personal hygiene, loss of interest in life activities, disturbed interpersonal relationships, trouble succeeding at work or school, detached manner, empty appearance and the inability to express emotion.

One of the rarest psychotic disorders is Shared Psychotic Disorder or folie a deux ("the folly of two"). This is a delusional disorder that is shared by two people that have close emotional ties. It involves the primary person who has a psychotic disorder such as schizophrenia and then a secondary person who is ordinary and otherwise healthy who shares the delusions of the primary person. For example, if the primary person believes that they have special powers that will help them take over the world, then the secondary person also begins to believe this. These delusions are induced and usually disappear when the two people are separated. Although it is not as likely, it can occur in groups of people who are associated with a person who has a psychotic disorder. The most significant case reported involved an entire family of twelve people. This case was referred to as folie douze. Shared Psychotic Disorder is also known by psychosis of association, contagious insanity, infectious insanity, double insanity and communicated insanity.

The only symptom of shared psychotic disorder is having the delusions of someone close to them that has a psychotic disorder. The cause remains unknown, but stress and social isolation are believed to play a role in the development of the disorder. The primary person often has a strong influence over the person with the shared psychotic disorder. This allows them to force their delusions or beliefs on the secondary person. Most of the time, the disorder occurs in a nuclear family. In fact, 95% of shared psychotic disorder cases are in the same family.

Making a correct diagnosis is difficult. If symptoms are present a doctor will perform a complete medical history and physical examination. There are no lab tests that can specifically diagnose shared psychotic disorder, but the doctor may use diagnostic tests such as x-rays or blood tests to rule out physical illness or drug-induced delusions. If no physical symptoms are present, the doctor may then refer the person to a psychiatrist or psychologist, who is trained to diagnose and treat mental illness. Clinical interviews are then required to properly diagnose shared psychotic disorder. There are three basic symptoms that are required to be present in order to make an accurate diagnosis. 1) A healthy person who has a close relationship with someone who has an established delusion develops a delusion themselves. 2) The content of the shared delusion closely resembles or is exactly like the established delusion. 3) Another psychotic disorder such as schizophrenia cannot account for the delusion that is manifested by the secondary person.

The goal of treatment is to relieve the secondary person's induced delusions and then to stabilize the primary person's psychotic disorder. Most of the time, the treatment includes separating the secondary person from the primary person. If separation is not possible then other approaches are taken as are appropriate for the situation. Psychotherapy, family therapy and medication are also part of the treatment regimen.

The prognosis for persons with shared psychotic disorder is generally good if the proper treatment is given; if the disorder is left untreated then it can become chronic.

Shared psychotic disorder is described as an uncommon pathological manifestation, therefore it is rarely found in general or social psychology text books. This disorder is almost completely unknown outside of abnormal psychology, psychiatry and psychopathology.