SHARED PSYCHOTIC DISORDER
Shared psychotic disorder, also known as folie à deux, is a rare psychiatric condition where two or more individuals who share a close relationship develop a shared delusion. In this condition, one person with an existing psychotic disorder influences and convinces another person or multiple nonpsychotic individuals to adopt their delusional belief. This phenomenon is most commonly observed between two individuals but can also occur in larger groups like families, which is referred to as folie à famille.
The history of shared psychotic disorder dates back to 1860 when Jules Baillarger first reported this unique mental state. Throughout the 19th century, various names were proposed for this condition in different European countries. In France, Baillarger referred to it as “folie communiquee” or “communicated psychosis.” In German psychiatry, Lehman and Sharfetter named it “Induziertes Irresein” or “induced insanity.” Eventually, the term “folie à deux” was coined by Lasegue and Falret in 1877, meaning “madness shared by two”.
Early research into shared psychotic disorder revealed four distinct types of the disorder. Gralnick, in the 1940s, classified these types based on his review of 103 cases. The classifications are as follows:
- Folie imposee (imposed psychosis): Described by Lasegue and Falret, this type involves the transfer of delusions from an individual with psychosis to an individual without psychosis in an intimate relationship. However, upon separation, the induced individual’s delusions gradually disappear.
- Folie simultanee (simultaneous psychosis): Regis coined this term to describe cases where both partners in a relationship simultaneously share the psychosis. Such cases often arise due to prolonged social interactions and the presence of common risk factors. In some instances, genetic risk factors have also been observed among siblings.
- Folie communiquée (communicated psychosis): This type, described by Marandon de Montyel, is similar to folie imposee. However, in this case, the delusion emerges after a prolonged period of resistance on the part of the secondary partner. Moreover, even upon separation from the primary partner, the secondary individual continues to exhibit and maintain the delusion.
- Folie induite (induced psychosis): Lehmann introduced this term to describe cases where an individual with an existing psychosis adopts new delusions under the influence of another individual with psychosis.
The Diagnostic and Statistical Manual of Mental Disorders has undergone changes in classifying shared psychotic disorder. It was initially recognized as shared paranoid disorder in DSM-III. Later, it was termed shared psychotic disorder in DSM-IV. In the most recent edition, DSM-5, shared psychotic disorder was removed as a separate disease entity and is now included within the section on other specified schizophrenia spectrum and other psychotic disorders. The International Classification of Diseases (ICD-10) lists it as induced delusional disorder.
The exact cause of shared psychotic disorder, also known as folie à deux, remains elusive. However, several risk factors have been identified that contribute to its development:
- Length of the relationship: Research suggests that a long duration of the relationship plays a significant role in the emergence of shared psychotic disorder. The attachment between individuals influences the adoption of the delusion.
- Nature of the relationship: Most cases of shared psychotic disorder occur within families. The most common relationships reported are between married or common-law couples, followed by sisters.
- Social isolation: Many cases involve individuals with limited social interaction. When faced with intimidating circumstances, a vulnerable person may be susceptible to the influence of another’s beliefs. The information received aligns with the primary individual’s experiences, gradually solidifying the shared delusion.
- Personality disorder: Individuals affected by shared psychotic disorder often exhibit features of personality disorders. Descriptions frequently include neuroticism, introversion, and emotional immaturity. Some cases indicate pre-existing personality disorders, particularly dependent (passive), schizoid, and schizotypal.
- Untreated mental disorder in the primary individual: A primary individual with an untreated chronic mental condition can pose a social risk factor for influencing their partner or family members. Delusional disorder is the most commonly observed diagnosis among the primary individuals, followed by schizophrenia and affective disorders.
- Cognitive impairment: Secondary individuals often show deficiencies in judgment and intelligence.
- Comorbidity of the secondary individual: An individual diagnosed with a mental disorder such as schizophrenia, bipolar affective disorder, depression, dementia, or intellectual disability is at higher risk of being influenced by another mentally ill person.
- Life events: Stressful life events impacting the relationship can contribute to the adoption of certain delusions, weakening resistance to intense emotions or thoughts. For instance, a wife affected by longstanding delusions may accuse her husband, who is experiencing erectile dysfunction, of having an affair or being “stimulated by sildenafil and narcotics.” The husband’s unstable and passive personality, combined with his challenging circumstances, may eventually lead him to accept this belief.
- Communication difficulties: Difficulty in expressing ideas and thoughts may contribute to a preference for isolation. Improving communication within dyadic relationships through multiple-conjoint psychotherapy may assist partners in understanding different perspectives and dismantling rigid and inflexible thinking patterns.
- Age and gender: While previous studies reported age differences with the older individual being the inducer and the younger being the induced, recent studies have challenged this finding. Shared psychotic disorder appears to be more common among females, regardless of whether they are the primary or secondary individuals.
The presentation of shared delusion varies depending on the specific type. In most cases, one partner encounters a problem in society that requires the involvement of a psychiatrist. This issue is often influenced or supported by the other partner. Both individuals exhibit unshakable false beliefs that are fixed and unrealistic. They may experience feelings of paranoia, fear, and suspicion towards a neighbor or someone within their community. The primary partner might seek mental assessment due to risky behavior, making unreal claims, or recent acts of aggression. The secondary partner, upon seeking help, may discover that others within their social circle share the same delusion as the primary individual.
Occasionally, cases of shared delusion can go undetected within a community for several years before being brought to light. In some instances, partners who share particular delusions may be admitted to the hospital together as a result of risky behavior or harm inflicted upon themselves or others.
In terms of general description, couples affected by shared delusion tend to be well-groomed and neatly dressed. When it comes to behavior, they may exhibit defensiveness or anger towards interviewers who challenge their delusions. Their speech is typically coherent and relevant. Mood and affect are often congruent with the specific delusion; for example, a paranoid patient may display irritability, while a grandiose patient may exhibit euphoria.
In terms of thought, their thinking is usually goal-oriented. The shared delusions can encompass the entire belief system or only part of it. They are often not bizarre in content and have a systematic structure. Additionally, these delusions tend to overvalue social, cultural, or religious beliefs beyond the norms of the community. Homicidal or suicidal ideation can also be present.
Abnormal perceptions are less likely to be expressed unless there are predisposing factors. Sometimes, only the secondary partner experiences some form of hallucination.
Orientation and cognition are usually intact, with the patient being aware of time, place, and person unless driven by their delusion. Memory and cognitive functioning are generally unaffected.
It is important to evaluate the patient for suicidal or homicidal ideation and plans. If there is a history of aggression with adverse outcomes, hospitalization should be considered.
Insight into their mental illness is typically lacking in both the primary patient and their partner. Judgment can be assessed by inquiring about past behavior and any future plans.