Folie à deux is the name for a condition where an otherwise sane person develops the symptoms and delusions of a person suffering from psychosis. If more than two people share the symptoms or delusions, people speak about "folie à trois" (3), "folie à quatre" (4), "folie à plusieurs", or "folie en famille". Officially, the condition is known as induced delusional disorder or shared psychotic disorder today, but many publications still use the original terms, which were developed in France in the 19th century.