Dissociative identity disorder (DID), also known as multiple personality disorder, is a condition where a person experiences distinct personalities or identities that control their behavior at different times. People with DID may experience memory loss and not remember the transitions between personalities. Symptoms include having multiple identities with different names, histories, and behaviors that emerge in stressful situations. Treatment focuses on long-term psychotherapy to help integrate the personalities and manage associated depression, anxiety, and self-harm.