Dissociative Identity Disorder (DID), also known as Multiple Personality Disorder, is a condition where a person has two or more distinct personalities or identity states that repeatedly take control of behavior. It is caused by extremely traumatic events during childhood. Symptoms include memory loss, mood swings, and distinct personalities that differ in age, gender, and other traits. Treatment focuses on psychotherapy to help integrate the personalities and medication for other symptoms. Famous people believed to have had DID include former NFL player Herschel Walker.