Dissociative identity disorder (DID), formerly known as multiple personality disorder, is characterized by distinct personality states called alters that repeatedly take control of one's behavior. It is caused by extremely traumatic childhood abuse and develops as a coping mechanism. People with DID can have as few as two or as many as hundreds of distinct alters. Treatment involves psychotherapy to help alters communicate and integrate their identities. However, the validity of DID remains controversial due to concerns over misdiagnosis and the influence of therapists. Famous cases like The Three Faces of Eve and Sybil brought attention to the disorder.