Dissociative identity disorder, formerly referred to as multiple personality disorder, is a recognized psychological condition thought to be due to extensive childhood trauma or abuse. But it is also plagued with controversy. The two cases that brought the condition to medical and popular prominence are documented in the books "The Three Faces of Eve" and "Sybil" which document two actual patients but some of their personalities are now thought to be implanted by therapists. The books and subsequent movies lead to a surge in cases and claims of DID which involve an unrealistically high number of severe versus mild cases, established fakes and implants by therapists.
—David Foss