Dissociative Identity Disorder. Usually caused by trauma/abuse; means person has suffered things that a person isn’t built to endure and so the person dissociates to stay alive. Dissociation can mean spacing out, forgetting, and even coming up with new personalities so that there is part of you that is not affected by the abuse. It’s a controversial diagnosis, some think it can’t really happen. It includes the old category of Multiple Personality Disorder. That’s the short version. If you have other questions, I’ll answer to the best of my ability.