The document discusses dissociative identity disorder (DID), formerly known as multiple personality disorder. It notes that unlike popular portrayals, most people with DID work hard to hide the disorder and function well in daily life and jobs. However, subjects are at risk for substance abuse and relationship problems if abusive behavior is present. People with DID also commonly have other mental health issues like depression, PTSD, and self-harming behaviors. While dissociation is an effective survival technique, habitual use of it can lead to dysfunction even after traumatic events end.