Dissociative identity disorder (DID), previously known as multiple personality disorder, is a mental disorder characterized by at least two distinct and relatively enduring personality states. This is accompanied by memory gaps beyond what would be explained by ordinary forgetfulness. These states alternately show in a person's behavior; presentations, however, are variable. Other problems which often occur in people with DID include borderline personality disorder (BPD), post-traumatic stress disorder (PTSD), depression, substance use disorders, self-harm, or anxiety.
Some professionals believe the cause to be childhood trauma. In about 90% of cases, there is a history of abuse in childhood, while other cases are linked to experiences of war or health problems during childhood. Genetic factors are also believed to play a role.
Treatment generally involves supportive care and counselling. The condition usually persists without treatment. It's believed to affect about 2% of the general population and 3% of those admitted to hospitals with mental health problems in Europe and North America. DID is diagnosed about six times more often in females than males. The number of cases increased significantly in the latter half of the 20th century, along with the number of identities claimed by those affected.
DID is controversial within both psychiatry and the legal system. In court cases, it has been used as a rarely successful form of the insanity defense. It is unclear whether increased rates of the disorder are due to better recognition or to sociocultural factors such as media portrayals. The typical presenting symptoms in different regions of the world may also vary depending on how the disorder is depicted by the media.