A disorder characterized by a person's behavior being alternately taken over by two or more personalities. The disorder also involves an inability to recall personal information relating to some of the personalities.

The disorder is believed to be caused by several factors: overwhelming stress, a capacity to dissociate, the use of defense processes, lack of nurturing during childhood, and lack of protection in overwhelming situations. Identity in children must be formed as a developmental task. If the child is overwhelmed, the task is obstructed and a unified identity does not occur. Ninety-eight percent of the adults with this disorder report abuse as a child. War and disaster may play a role in this developmental disorder. In addition, loss of a parent, or a child who requires many hospitalizations and operations may be overwhelming.

This disorder tends to mimic other psychiatric disorders. These patients often, have been treated several times for different diagnoses and treatment has failed. Most patients experience some symptoms of depression, anxiety, panic attacks, eating disorders, posttraumatic stress, sexual dysfunction and self-injury with suicide attempts. Two characteristic symptoms are:

• Depersonalization - a feeling of being removed from oneself

• Derealization - the experiencing of familiar persons and surroundings as strange and unfamiliar.

Diagnosis is usually made with medical and psychiatric evaluation. The psychiatrist may attempt to bring forth the other personality or personalities for which the person had amnesia. Drug-induced interviews or hypnosis may be used to explore the dissociative phenomena, and patients are asked to keep a personal log between visits. The diagnostic criteria are as follows:

• The presence of two or more distinct identities or personality states.

• At least two of these identities or personality states recurrently take control of the person's behavior.

• Inability to recall vital personal information and it is too extensive to be attributed to ordinary forgetfulness.

• The disorder is not due to the effects of a substance or a general medical condition.

The treatment goal is to achieve integration; however, this disorder does not go away spontaneously. Treatment includes two or more psychotherapy sessions a week for 3 to 6 years. The therapy is divided into three phases:

• Initially, safety is a priority; the patient is stabilized and then strengthened to deal with the difficult issues and problem personalities.

• In the second phase, the patient is assisted to deal with the painful issues and grieve over the losses. When the reason for the dissociation is addressed, the patient can move into the final phase.

• The final phase is focused on reconnecting and integrating. The patient's selves and relationships are rehabilitated and social functioning is re-instituted. Hypnotic suggestion or imagery is used to help unify these personalities. When integration is attained, treatment will continue in order to deal with unresolved issues.

Most patients continue to see their psychiatrist and do not terminate therapy because they have come to think of the psychiatrist as necessary to help them deal with issues.