Dissociative identity disorder (DID), previously known as multiple personality disorder, is characterized by at least two distinct personality states. Each personality may have its own sense of self, habits, and memories. DID occurs more frequently in women and is thought to develop from traumatic experiences in early childhood. Symptoms include gaps in memory, switching between identities, depersonalization, and derealization. Treatment focuses on psychotherapy and hypnotherapy to help integrate the alternate personalities.