Folie à deux
| Induced delusional disorder | |
|---|---|
| Classification and external resources | |
| Specialty | psychiatry |
| ICD-10 | F24 |
| ICD-9-CM | 297.3 |
| DiseasesDB | 34350 |
| eMedicine | med/3352 |
| MeSH | D012753 |
Folie à deux (/fɒˈli ə ˈduː/; French pronunciation: [fɔli a dø]; French for "madness of two"), or shared psychosis, is a psychiatric syndrome in which symptoms of a delusional belief and hallucinations are transmitted from one individual to another. The same syndrome shared by more than two people may be called folie à trois, folie à quatre, folie en famille or even folie à plusieurs ("madness of many"). Recent psychiatric classifications refer to the syndrome as shared psychotic disorder (DSM-IV) (297.3) and induced delusional disorder (F.24) in the ICD-10, although the research literature largely uses the original name. This disorder is not in the current DSM (DSM-5). The disorder was first conceptualized in 19th-century French psychiatry by Charles Lasègue and Jean-Pierre Falret and so also known as Lasègue-Falret Syndrome.
This syndrome is most commonly diagnosed when the two or more individuals concerned live in proximity and may be socially or physically isolated and have little interaction with other people.
Various sub-classifications of folie à deux have been proposed to describe how the delusional belief comes to be held by more than one person.
Folie à deux and its more populous cousins are in many ways a psychiatric curiosity. The current Diagnostic and Statistical Manual of Mental Disorders states that a person cannot be diagnosed as being delusional if the belief in question is one "ordinarily accepted by other members of the person's culture or subculture" (see entry for delusion). It is not clear at what point a belief considered to be delusional escapes from the folie à... diagnostic category and becomes legitimate because of the number of people holding it. When a large number of people may come to believe obviously false and potentially distressing things based purely on hearsay, these beliefs are not considered to be clinical delusions by the psychiatric profession and are labelled instead as mass hysteria.
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