[A case of folie à trois]

We examined a case of a family of induced insanity (folie à trois) which is characterized by its delusion of jealousy, and reported about the establishment and disappearance process of the delusion. We examined the background of the fact that the family members shared the same delusion and the family dynamics. We concluded that induced insanity is an extended expression of family illness which appears in the process in which the family expresses its problematic theme and tries to cope with it.