Dissociative identity disorder (DID) is a mental disorder characterized by the maintenance of at least two distinct and relatively enduring personality states. The disorder is accompanied by memory gaps beyond what would be explained by ordinary forgetfulness. The personality states alternately show in a person’s behavior; however, presentations of the disorder vary.
Other conditions that often occur in people with DID include post-traumatic stress disorder, personality disorders (especially borderline and avoidant), depression, substance use disorders, conversion disorder, somatic symptom disorder, eating disorders, obsessive–compulsive disorder, and sleep disorders. Self-harm, non-epileptic seizures, flashbacks with amnesia for content of flashbacks, anxiety disorders, and suicidality are also common.
DID is associated with overwhelming traumas, or abuse during childhood. In about 90% of cases, there is a history of abuse in childhood, while other cases are linked to experiences of war, or medical procedures during childhood.
Genetic and biological factors are also believed to play a role. The diagnosis should not be made if the person’s condition is better accounted for by substance use disorder, seizures, other mental health problems, imaginative play in children, or religious practices.
Despite research on DID including structural and functional imaging findings have been identified regarding DID, making it difficult to hypothesize a biological basis for DID. In addition, many of the studies that do exist were performed from an explicitly trauma-based position, and did not consider the possibility of therapy as a cause of DID.
There is no research to date regarding the neuroimaging and introduction of false memories in DID patients, though there is evidence of changes in visual parameters and support for amnesia between alters. DID patients also appear to show deficiencies in tests of conscious control of attention and memorization (which also showed signs of compartmentalization for implicit memory between alters but no such compartmentalization for verbal memory) and increased and persistent vigilance and startle responses to sound.
Treatment generally involves supportive care and psychotherapy. The condition usually persists without treatment. It is believed to affect about 1.5% of the general population (based on a small US community sample) and 3% of those admitted to hospitals with mental health issues in Europe and North America.
DID is diagnosed about six times more often in females than males. The number of recorded 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 sociocultural factors such as mass media portrayals.
The typical presenting symptoms in different regions of the world may also vary depending on culture, for example alter identities taking the form of possessing spirits, deities, ghosts, or mythical figures in cultures where normative possession states are common.
The possession form of dissociative identity disorder is involuntary and distressing, and occurs in a way that violates cultural or religious norms.