Previously called multiple personality disorder, dissociative identity disorder is a mental illness arising from traumatic events and/or abuse in childhood.

Symptoms (criteria for diagnosis) include:

* The existence of two or more distinct identities (or “personality states”).

* Ongoing gaps in memory about everyday events, personal information, and/or past traumatic events.

The symptoms cause significant problems in social, occupational, or other areas of functioning. The attitude and personal preferences (e.g., about food, activities, clothes) of a person with this disorder may suddenly shift and then shift back. The identities happen involuntarily and cause distress.