Shared delusional disorder

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
Shared delusional disorder

Shared delusional disorder is a delusion that develops in someone who has a close relationship with a person with a preexisting psychological condition (called the primary case or inducer). In shared delusional disorder ( also called Folie à deux (insanity of two) or shared psychotic disorder) the primary case gradually passes on their delusion to a second, previously psychologically healthy individual. While the type of relationship between the primary case and the second person can be of any nature (i.e. parent and child, partners, siblings), it usually involves a very close relationship in which the two people have been living with each other for many years in an environment of social isolation. Within the relationship, the dominant person gradually passes on their delusion to the weaker, more submissive person. As a result, if that connection is broken, the delusion may go away or its own, or with treatment [1] ( refer to treatment section). As with most psychological disorders, the extent and type of delusion varies, however it usually mimics the delusion of the inducer and is almost very similar to it.[2] The inducer does not realize that they are making the other person sick but instead think they are helping by alerting the second person of what they deem to be "truth".

Type of delusions[edit]

Psychology Today magazine defines delusions as "fixed beliefs that do not change, even when a person is presented with conflicting evidence".[3] There are 4 main types of delusions that are passed on from an inducer to a secondary person: Bizarre delusions, Non-bizarre delusions, Mood-congruent delusions and Mood neutral delusions.

  • Bizarre delusions are clearly implausible and not understood by peers within the same culture, even those with psychological disorders. For example, if Jean thought that all of her organs had been taken out and replaced by someone else's while they were asleep without leaving any scar and without her waking up. Not only is it impossible for someone to survive having all their organs taken out and replaced, but if they did survive they would be covered in scars, need bottles of anti-rejection and pain medication, would be in crippling amounts of pain, and would not be able to move.
  • Non-bizarre delusions are common among those with personality disorders and are understood by people within the same culture. For example, if Lindsey thinks that the FBI is following her in unmarked cars and watching her via security cameras she is having a non-bizarre delusion. While this is highly unlikely for the average person, it is possible and therefore understood by those around her.
  • Mood congruent delusions correspond to a person's emotions at the time, usually during an episode of mania or depression. For example, someone with this type of delusion may believe that they are going to win $2 million at the casino tonight, despite the fact that the majority of people who go to a casino walk away having lost money or in some cases leave with some money, but rarely over $100 and never 2 million. Similarly, someone in a depressive state may believe that their mother will get hit by lightning tomorrow, despite the fact that in Canada only 120 people get hit by lightning per year ( out of a population of 37 million).
  • Mood neutral delusions are the opposite of mood-congruent delusions because they are unrelated to mood. They can be either bizarre or non-bizarre so long as they are not affected by whether that person is in a manic or depressive stage. The formal definition provided by Mental health daily is " a false belief that isn't directly related to the person's emotional state". An example would be if Henry thinks that somebody switched bodies with his neighbor, as it as nothing to do with his mood [4][5]


No-one knows what causes SDD exactly but stress and social isolation are the main contributors.[6] When we are socially isolated the few people we do talk to become very important to us, and therefore they are seen as more trustworthy, so when an inducer is sharing their delusions, the second person is more likely to believe them. Additionally, since they are socially isolated people developing shared delusional disorder do not have others reminding them that their delusions are either impossible or not likely and are therefore more likely to develop SDD. In fact, the treatment for shared delusional disorder is for the person to be removed for the inducer and seek additional treatment if necessary.[7]

Stress is also a factor because it triggers mental illness. The majority of people that develop shared delusional disorder are genetically predisposed to mental illness, however this predisposition ( i.e. genes for schizophrenia that need to be activated) is not enough to develop a mental disorder. However, when that person becomes stressed their adrenal gland releases the stress hormone cortisol into the body which released increased levels of dopamine in their brain and changes in dopamine levels are linked to mental illness.[8] As a result, stress puts one at a heightened risk of developing a psychological disorder such as shared delusional disorder.


Shared delusional disorder is hard to diagnose because usually, the afflicted person does not seek out treatment because they do not realize that their delusion is abnormal as it comes from someone in a dominant position who they trust. Furthermore, since their delusion comes on gradually and grows in strength over time, their doubt is slowly weakened during this time. Shared delusional disorder is diagnosed using the DSM-5 and according to this the person afflicted must meet three criteria:

  • They must have a delusion that develops in the context of a close relationship with an individual with an already established delusion.
  • The delusion must be very similar or even identical to the one already established one that the primary case has.
  • The delusion cannot be explained by any other psychological disorder, mood disorder with psychological features, a direct result of physiological effects of substance abuse or any general medical condition [9]


After a person has been diagnosed, the next step is to determine the proper course of treatment. The first step is to separate the formerly healthy person from the inducer and see if the delusion goes away or lessens over time. If this is not enough to stop the delusions there are two possible courses of action: Medication or therapy which is then broken down into personal therapy and/or family therapy.

  • Medication: if the separation alone is not working, antipsychotics are often prescribed for a short time to prevent the delusions. Antipsychotics are medications that reduce or relieve symptoms of psychosis such as delusions or hallucinations (seeing or hearing something that is not there). Other uses of antipsychotics include stabilizing moods for people with mood swings and mood disorders ( i.e. in bipolar patients), reducing anxiety in anxiety disorders and lessening tics in people with Tourettes. Antipsychotics do not cure psychosis but they do help reduce the symptoms and when paired with therapy, the afflicted person has the best chance of recovering. While antipsychotics are powerful, and often effective, they do have side effects such as inducing involuntary movements and should only be taken if absolutely required and under the supervision of a psychiatrist.[10]
  • Therapy: the two most common forms of therapy for people suffering from shared delusional disorder are personal and family therapy. Personal therapy is one-on-one counseling that focuses on building a relationship between the counselor and the patient and aims to create a positive environment where the patient feels that they can speak freely and truthfully. This is advantageous because the counselor can usually get more information out of the patient to get a better idea of how to help them if that patient feels safe and trusts them. Additionally if the patient trusts what the counsellor says disproving the delusion will be easier.[11]

Family therapy is a technique in which the entire family comes into therapy together to work on their relationships and to find ways to eliminate the delusion within the family dynamic. For example, if someone's sister is the inducer the family will have to get involved to ensure the two stay apart and to sort out how the family dynamic will work around that. The more support a patient has the more likely they are to recover, especially since SDD usually occurs because of social isolation.[12]

With treatment, the delusions and therefore the disease will eventually lessen so much so that it will practically disappear in most cases. However left untreated it can become chronic and lead to anxiety, depression, aggressive behavior and further social isolation. Additionally Unfortunately there are not many statistics about the prognosis of shared delusional disorder as it is a rare disease and it is expected that the majority of cases go unreported; however, with treatment, the prognosis is very good.


Shared delusional disorder is most commonly found in woman with a slightly above average IQs, who are isolated from their family that are in relationships with a dominant person who has delusions. The majority of secondary cases ( people who develop the shared delusion) also meet the criteria for Dependent Personality Disorder [13] which is characterized by a pervasive fear that leads them to need constant reassurance, support and guidance.[14] Additionally 55% of secondary cases had a relative with a psychological disorder that included delusions and, as a result, the secondary cases are usually susceptible to mental illness.[15] With this being said, this disorder can also occur in cults where it has its most devastating effects. One example of this is the case of the Heaven's Gate Cult, a UFO religious militarism cult led by Marshall Applewhite who had delusions about extraterrestrial life. Unfortunately, the members of the cult developed this delusion as well and killed themselves with the intention of their spirits joining an extraterrestrial spacecraft heading towards a comet.[16] This shows the tragic effects of this disorder and how powerful it can be.

Biopsychosocial effects[edit]

As with most, if not all personality disorders, shared delusional disorder affects the psychological and social aspects of the person's life. Biologically, since most delusions are accompanied by fear and paranoia, they increase the amount of stress experienced. For example, if Lisa believes that radiation from the sun is poisoning her food she is going to be extremely stressed and fearful for her life. Increased stress will negatively affect her physical health because stress increases blood pressure, heart rate and breathing rates which put her at risk of developing cardiovascular disease. Additionally, she will be at an increased risk of developing diabetes, becoming obese and the functioning of her immune system will be lessened as a result of stress.[17] These health risks increase with the severity of the disease, especially if the condition is left untreated and becomes chronic, leading to the development of anxiety and depression.

In fact, delusional disorder puts those affected with it at a heightened risk of developing other psychological disorder such as anxiety and depression. This is because 55% of people with shared delusional disorder are genetically predisposed to psychological disorders like bipolar disorder, schizophrenia, anxiety, and depression...etc. This predisposition is usually triggered by the heightened state of fear, worry, and hopelessness experienced by those with SDD through increased levels of cortisol and therefore dopamine levels.[18] Since shared delusional disorder itself is a very frightening and stressful disorder to live with, adding anxiety which is characterized by nervousness, worry, fear and apprehension [19] and depression, a state of despondency and dejection makes their life impossibly difficult.

The most obvious effect of shared personality disorder is probably the isolation from society. If Chris believes that the FBI is stalking him or that there are people trying to hurt him, he is going to disassociate from society and stop talking to most people, especially if he senses any hostility or lack of belief in this delusion. Since shared delusional disorder usually occurs in those who are socially isolated, further isolation will only make the disorder worse as it will pull the secondary person closer to the inducer and away from anyone trying to help them.

See also[edit]


  1. ^ "Symptoms of Shared Psychotic Disorder". Retrieved 2018-03-22.
  2. ^ "Shared Psychotic Disorder Symptoms - Psych Central". Psych Central. 2016-05-17. Retrieved 2018-03-22.
  3. ^ "Delusional Disorder | Psychology Today". Psychology Today. Retrieved 2018-03-22.
  4. ^ "Delusion Types". 2010-08-15. Retrieved 2018-03-22.
  5. ^ "4 Types of Delusions & Extensive List of Themes - Mental Health Daily". Mental Health Daily. 2015-04-29. Retrieved 2018-03-22.
  6. ^ "Shared Psychotic Disorder - Treatment Options". Retrieved 2018-03-22.
  7. ^ "Symptoms of Shared Psychotic Disorder". Retrieved 2018-03-22.
  8. ^ "Stress May Trigger Mental Illness and Depression In Teens". Retrieved 2018-03-22.
  9. ^ "Shared Psychotic Disorder Symptoms - Psych Central". Psych Central. 2016-05-17. Retrieved 2018-03-22.
  10. ^ "CAMH: Antipsychotic Medication". Retrieved 2018-03-22.
  11. ^ "Benefits of Individual Therapy | Therapy Groups". Retrieved 2018-03-22.
  12. ^ "Teen Treatment Center Blog". Teen Treatment Center. Retrieved 2018-03-22.
  13. ^ "Shared psychotic disorder - causes, effects, therapy, drug, person, people, medication, personality, theory". Retrieved 2018-03-22.
  14. ^ "Dependent Personality Disorder Symptoms - Psych Central". Psych Central. 2017-12-17. Retrieved 2018-03-22.
  15. ^ "Shared psychotic disorder - causes, effects, therapy, drug, person, people, medication, personality, theory". Retrieved 2018-03-22.
  16. ^ "Heaven's Gate (religious group) - Wikipedia". Retrieved 2018-03-22.
  17. ^ "How stress affects your body and behavior". Mayo Clinic. Retrieved 2018-03-22.
  18. ^ "Stress May Trigger Mental Illness and Depression In Teens". Retrieved 2018-03-22.
  19. ^ "Anxiety: Causes, symptoms, and treatments". Medical News Today. Retrieved 2018-03-22.

External links[edit]