Folie à deux
Rare syndrome of shared delusional belief between two or more people.
Folie à deux—French for "madness of two"—is a rare psychiatric condition also called shared psychosis or shared delusional disorder (SDD). In this syndrome, a delusional belief passes from one person to another. It was first described in 19th-century French psychiatry by Charles Lasègue and Jules Falret, and is sometimes referred to as Lasègue–Falret syndrome. More recent classification systems have used terms like shared psychotic disorder (DSM-IV, code 297.3) and induced delusional disorder (ICD-10, code F24), though the original name remains common in research. When more than two people share the same delusion, it may be called folie à trois (three) or folie à quatre (four), and broader cases are known as folie en famille (family madness) or folie à plusieurs (madness of several). The current edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) does not list this syndrome as a separate diagnosis, finding the criteria insufficient or inadequate. Instead, clinicians should classify it as "Delusional Disorder" or under "Other Specified Schizophrenia Spectrum and Other Psychotic Disorder."
The syndrome is most often diagnosed when the individuals involved live close together, are socially or physically isolated, and have limited contact with others. Several subtypes have been proposed to explain how the delusion spreads. In folie imposée (imposed psychosis), a dominant person—the primary, inducer, or principal—first develops a delusion during a psychotic episode and then imposes it on another person or persons (the secondary, acceptor, or associate). The secondary person, described as "un malade par reflet," typically does not have a true psychosis; if the two are admitted to separate hospitals, the induced person’s delusions usually fade. In folie simultanée (simultaneous psychosis), either two people who independently experience psychosis influence each other’s delusions until they become identical or very similar, or two people already predisposed to delusional psychosis trigger symptoms in one another. Because there is no dominant partner, separating them may not improve either person’s condition.
- Known for
- Shared delusional disorder (folie à deux)
- First conceptualized by
- Charles Lasègue and Jules Falret
- Also known as
- Lasègue–Falret syndrome, shared psychotic disorder, induced delusional disorder
- Dsm-5 status
- Not a separate entity; classified as Delusional Disorder or Other Specified Schizophrenia Spectrum and Other Psychotic Disorder
Lore & Background
Folie à deux is most commonly diagnosed when individuals live in proximity, are socially or physically isolated, and have little interaction with other people. Several sub-classifications have been proposed: folie imposée, where a dominant person imposes a delusion on a secondary person who typically abandons the delusion if separated; folie simultanée, where two people independently experiencing psychosis influence each other's delusions; folie communiquée, where the secondary person develops their own delusional content and separation does not improve the condition; and folie induite, where the delusion of one person with psychosis is enhanced by another's delusional content.
Reader's Guide
Folie à deux remains a psychiatric curiosity, with its diagnostic status disputed. The DSM-5 does not recognize it as a separate disorder, directing clinicians to classify it under Delusional Disorder or Other Specified Schizophrenia Spectrum and Other Psychotic Disorder. The syndrome highlights the boundary between shared delusion and culturally accepted belief: the manual states a person cannot be diagnosed as delusional if the belief is ordinarily accepted by their culture or subculture. When many people hold an obviously false belief based on hearsay, it is labeled mass hysteria rather than clinical delusion. The disorder's causes are unknown, but stress and social isolation are main contributors. Treatment includes separating affected individuals from the inducer. Shared delusional disorder can negatively impact psychological and social wellbeing, increasing risk of comorbidities such as depression and anxiety, and is associated with a genetic pattern shared by 55% of patients.
Did You Know?
- The same syndrome shared by more than two people may be called folie à trois, folie à quatre, folie en famille, or folie à plusieurs.
- In folie imposée, if the parties are admitted to hospital separately, the delusions in the person with induced beliefs are typically abandoned.
- The DSM-5 does not consider shared psychotic disorder as a separate entity, citing insufficient or inadequate criteria.
- People with a delusional disorder have a significantly high risk of developing psychiatric comorbidities such as depression and anxiety, possibly attributable to a genetic pattern shared by 55% of SDD patients.
More in Psychopathological syndromes 1-24
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