Folie a deux

“Folie a deux” or “Shared Psychotic Disorder” is a rare type of mental illness in which a person who does not have a primary mental health disorder comes to believe the delusion of a close person with a psychotic or delusional disorder. For example, a wife might come to believe her husband’s delusions even though she is otherwise mentally healthy. 

Shared Psychotic Disorder develops in the context of a relationship in which one person influences the other. The psychotic symptoms develop in the course of a close long-term relationship with a person who already had a psychotic disorder. These relationships can for example be between family members, couples, sisters and in rare cases can even include more than two individuals. The person with a preexisting disorder is called the primary case (Inducer) and the other person is called the secondary case (Inductee or Recipient).

The symptoms of shared psychotic disorder depend on the diagnosis of the primary person with the disorder. The secondary person develops hallucinations or delusions gradually over time and is usually not aware of these changes. Neither the person with the primary mental illness nor the person who develops the same delusions has insight into the problem. Therefore, the first person does not realize that they are making the other person sick. They assume that they are simply showing the truth to the second person.

In general, both individuals behave paranoid, fearful, and distrustful of others. They react very defensive and angry if their shared delusions are questioned. The delusions themselves are usually persecutory. With the separation of the primary and the secondary person, the developed delusions from the secondary person seem to disappear.

 But what causes this extraordinary disorder? There are several possible risk factors for “Shared Psychotic Disorder”:

  • Social isolation of the primary and secondary person from the outside world
  • High levels of chronic stress or the occurrence of stressful life events
  • A dominant primary person and submissive secondary person 
  • A close connection between the primary and secondary person; usually a long-term relationship with attachment (e.g., family members, couples, sisters, etc.)
  • A secondary person with a neurotic, dependent, or passive personality style or someone who struggles with judgment/critical thinking
  • A secondary person with another mental illness such as depression, schizophrenia, or dementia
  • An untreated disorder (e.g., delusional disorder, schizophrenia, bipolar disorder) in the primary individual
  • An age difference between the primary and secondary person
  • A secondary person who is dependent on the primary due to being disabled (e.g., physically or mentally)

To get a better impression of the Shared Psychotic disorder I show you a case described by Mohamed in which an 8-year-old girl was admitted to a psychiatric center. The girl had acute psychosis with agitation, confusion, paranoid delusions, and hallucinations. The girl reported that her neighbors broke into her house, raped her, and injected her with drugs and rat poison. She also stated hearing the neighbors’ voices and additionally suffered from insomnia, and has trouble falling asleep. The girl had no history of psychiatric or medical illness according to her family and her primary care physician. Examinations showed that the 8-year-old had no physical signs of needlesticks or rape, and her mental status was normal except for the paranoid content of her thoughts. When attempts were made to contact the mother, it was discovered that the mother had checked herself into the same psychiatric clinic. The mother reported to her psychiatrist about the same atrocities committed by the neighbors as her daughter. In her records, it was found that the mother had been to the emergency department several times before and reported similar symptoms. The mother always refused psychiatric assessment or treatment. 

After a full assessment, it was revealed that there were no signs of genital trauma and any kind of drugs. The daughter was diagnosed with Shared Psychotic Disorder and the mother was diagnosed with Psychotic Disorder Not Otherwise Specified. 

After the diagnosis, the daughter was separated from her mother and was able to recover quickly. The daughter was left in the care of a family friend. The mother went for treatment and was able to see her daughter under supervision.

Bibliography :
  • Abu-Salha, M. (1998). Folie á Deux: Two Case Reports. Jefferson Journal of Psychiatry, 14(1).
Featured image :
  • Canva. (n.d.).