Dissociative Identity Disorder (DID), also known as Multiple Personality Disorder, is a mood disorder where an individual's behavior is controlled by two or more distinct personality states. Symptoms include split identities, memory variations between personalities, mood swings, and hallucinations. Causes are believed to involve childhood trauma, and treatment focuses on psychotherapy, medication, and hypnosis to stabilize and unite the personalities. People with DID experience confusion, loss of identity and memory, anger, depression, and frustration due to unpredictable personality changes.