Folie à deux (literally, "a madness shared by two") is a rare psychiatric syndrome in which a symptom of psychosis (particularly a paranoid or delusional belief) is transmitted from one individual to another. The same syndrome shared by more that one person may be called folie à trois, folie à quatre, folie à 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 (folie à deux) (F.24) in the ICD-10, although the research literature largely uses the original name.