Dissociative identity disorder is associated with overwhelming experiences, traumatic events and/or abuse that occurred in childhood. Dissociative identity disorder was previously referred to as multiple personality disorder.

Symptoms of dissociative identity disorder (criteria for diagnosis) include:

• The existence of two or more distinct identities (or “personality states”). The distinct identities are accompanied by changes in behaviour, memory and thinking. The signs and symptoms may be observed by others or reported by the individual.
• Ongoing gaps in memory about everyday events, personal information and/or past traumatic events.
• The symptoms cause significant distress or problems in social, occupational or other areas of functioning.

The attitude and personal preferences (for example, about food, activities, clothes) of a person with dissociative identity disorder may suddenly shift and then shift back. The identities happen involuntarily and are unwanted and cause distress. People with dissociative identity disorder may feel that they have suddenly become observers of their own speech and actions, or their bodies may feel different (e.g., like a small child, like the opposite gender, huge and muscular).