What is Shared Psychotic Disorder?

According to the National Institute of Health (NIH), shared psychotic disorder (folie à deux) is a rare disorder characterized by sharing a specific delusion among two or more people in a close relationship. The inducer (primary) who has a psychotic disorder with delusions influences another individual or more (induced, secondary) based on a delusional belief. It is commonly seen among two individuals, but in rare cases, can include larger groups. This activity outlines the presentation and management of shared psychotic disorder and highlights the role of the interprofessional team in improving the care of patients with this condition. Arlin Cuncic, MA, at Very Well Mind, describes shared psychotic disorder as a rare type of mental illness in which a person who does not have a primary mental health disorder comes to believe the delusions of another person with a psychotic or delusional disorder. For example, a wife might come to believe the delusions of her husband, despite having otherwise good mental health.

Shared psychotic disorder was first identified in 1860 by Baillarger. It then came to be known under a number of different terms. These include the following:

  • “Folie a deux” (madness shared by two) or “folie imposeé” coined by Lasegue and Falret in 1877
  • “Folie communiqueé” (communicated psychosis) coined by Marandon de Montyel in 1881
  • “Folie simultaneé” (simultaneous psychosis; in which both parties live with primary delusions that they transmit to each other) coined by Regis in 1880; also known as “folie induite” coined by Lehman in 1885

The incidence of shared psychotic disorder is reported to be low (1.7 to 2.6% of hospital admissions). However, it’s likely that many cases go unreported.



The symptoms of shared psychotic disorder will vary depending on the specific diagnosis of the primary person with the disorder. However, there are some features of the disorder that will be similar across cases.

Secondary Effects

Living with delusions can have effects on the physical health of both persons with the disorder due to increased stress (e.g., elevated cortisol levels). Secondary mental health issues may develop such as anxiety and depression due to prolonged stress and fear. Due to the nature of the psychotic illness, both individuals may not be in touch with reality and struggle with aspects of daily living.

Primary Symptoms

Neither the person with the primary mental illness nor the person who develops the same delusions has insight into the problem or awareness that what they believe is not the truth. The secondary person will generally develop the delusions gradually over time in a way that their normal doubt or skepticism becomes reduced. Depending on the nature of the primary illness, that individual may experience hallucinations (seeing or hearing things that aren’t there) or delusions (believing things that are not true, even when shown evidence of that fact). Delusions may be bizarre, non-bizarre, mood-congruent, or mood-neutral (related to bipolar disorder). Bizarre delusions are things that are physically impossible and that most people would agree could never happen, while non-bizarre delusions are things that are possible but highly improbable. Mood-congruent delusions match your mood (depressed or manic). For example, a person in manic state might believe that they are about to win a big sum at the casino. In contrast, a person in a depressed state might think that their relatives are going to die in a plane accident.

Below are some other examples of possible delusions:

  • Thinking that radiation is being transmitted into your home by a foreign country to cause stomach upset or diarrhea.
  • Thinking that the FBI is tapping your phone or that your family is being followed.
  • Believing that you will soon be awarded a large sum of money.
  • Thinking that your neighbors are somehow poisoning your food supply or water lines.

In general, both persons will act paranoid, fearful, and suspicious of others. They will also become defensive or angry if their delusions are challenged. Those with grandiose delusions might appear euphoric. The primary person in the relationship will not recognize that they are making the other person ill. Instead, they think that they are simply showing them the truth, because they have no insight into their own mental illness. In terms of the secondary person, that person may exhibit dependent personality traits, in the form of fear and needing reassurance. These individuals are often susceptible to mental illness themselves in terms of having relatives with diagnosed illnesses. Common dyads include husband-wife (married or common-law), mother-daughter, sister-sister, or parent-child.


What causes a secondary person to take on the delusions of someone with a psychotic or delusional disorder? There are several possible risk factors including the following:

  • Social isolation of the primary and secondary person from the outside world (when there is no social comparison, it becomes impossible to tell apart fact from delusion)
  • High levels of chronic stress or the occurrence of stressful life events
  • A dominant primary person and submissive secondary person (the secondary person may agree at first to keep the peace, and over time come to believe the delusion)
  • 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)
  • Either the primary or secondary person being female (shared psychotic disorder is more common among women)



How is shared psychotic disorder diagnosed? When it first appeared in the Diagnostic and Statistical Manual of Mental Disorders (DSM-III) it was diagnosed as “shared paranoid disorder.”

Then, in the DSM-IV, it was diagnosed as “shared psychotic disorder.” Finally, in the most recent DSM-5, it is no longer identified as a separate diagnosis; rather, it is diagnosed under Section 298.9: Other specific schizophrenia spectrum and other psychotic disorder. The specific description is given below:

Finally, in the International Classification of Diseases (ICD-11), this illness is diagnosed as an induced delusional disorder.

Overall, this disorder tends to go undiagnosed or is missed, because neither person generally has insight into their mental illness. Typically, the cases will only come to light if the primary person acts out on a delusion, which draws attention to the situation. For example, a person with a paranoid delusion about a neighbor might commit an assault.

However, even if the primary person presents for treatment, treatment providers may not be aware that there is a secondary person who is affected. For this reason, these types of cases may go undiscovered for a long time.

In order to diagnose the secondary person as having this disorder, it is necessary that their delusions develop as a result of contact with the primary person, that their delusions are similar in nature to those of the primary person, and that their symptoms can’t be explained by some other issue such as a medical condition or substance abuse.

Finally, the steps in a diagnosis involve the following:

  • A clinical interview and medical exam; while there are no tests to identify this illness, other problems can be ruled out using tests such as brain imaging, MRI scans, blood tests, and urine toxicology screen
  • A mental state examination
  • A history from a third party (to ensure accuracy of what is reported)


Finally, how is shared psychotic disorder treated? Since this disorder often goes undiagnosed, it is often just the primary person who receives treatment for their mental disorder. However, once the secondary person is identified, a team approach is required that may be composed of various professionals such as a doctor, nurse, pharmacist, mental health professionals, etc.

Since the disorder is rare, there is no standard treatment protocol. However, it is typical that the secondary person will be separated from the primary person as a first measure. Typically, this seems to help reduce the delusions in the secondary person.

Specific treatments that may be offered include the following:

  • Psychotherapy to ease emotional turmoil and shed light on dysfunctional thinking patterns
  • Family therapy to encourage healthy social relationships, promote medication adherence, and to help the secondary person develop interests outside the relationship
  • Medication such as antipsychotics, tranquilizers, antidepressants, or mood stabilizers may also be used depending on the symptoms of each individual.


Unfortunately, due to the nature of shared psychotic disorder, most people will require professional help and will not be able to overcome these issues on their own. However, if you are a person recovering from this illness, there are some things to keep in mind:

  • First, it is important to adhere to any treatment protocol that is prescribed.
  • Second, treatment will generally involve meeting with a therapist, and the relationship that you build and trust that is formed with that person is critical for getting better. For this reason, it is important to continue seeing a therapist even if it feels hard in the beginning.
  • Finally, when left untreated this disorder will be chronic and will not get better. If you suspect someone that you know or you yourself are living with shared psychotic disorder, do your best to reach out for help.

If you suspect that you or someone you know is living with shared psychotic disorder, it might be hard to disengage from the situation to decide what is the truth versus what is delusions. In this case, it’s best to reach out for help if you can, particularly if you are the secondary person in the relationship and struggle with feeling dependent on the primary person.

If you are the primary person in a situation involving shared psychotic disorder and you are receiving treatment from a professional, it is important to be forthcoming about the impact of your illness on those around you. Because this disorder is often missed or not detected, unless you share the details of your situation and how others are involved, it’s unlikely that the secondary person will receive help.

The bottom line is that it can be very scary and unsettling to live with delusions; however, the only way to improve the situation is to reach out for help, start regaining social ties outside the narrow relationship that has developed, and receive therapy and/or medication as needed. It is only when these steps have been taken that you are likely to see improvement in your situation.

In particular, if the secondary person is a child or dependent and cannot reach out for help themselves, it is important that others step in and recognize the situation so that aid can be provided.

This article is provided by Dr. Ralph Kueche (Child Psychologist). Dr. Kuechle is a Child and Adolescent Clinical Psychologist who specializes in treating children and their families who may be struggling with mood and behavioral issues. Learn more about Dr. Kuechle.