Dissociative identity disorder is a controversial clinical diagnosis in psychiatry. Although it's a recognized diagnosis, there's controversy about whether it's a separate disorder or merely a manifestation of other psychiatric disorders. In addition, there's ample evidence that the disorder may more commonly be caused by the intervention of the therapist - the case of "Sybil", who manifested 16 separate personalities, has since been shown to have been an attempt by a very neurotic patient to gain the attention and favor of their therapist.
In any event, the condition has two primary diagnostic criteria:
- The patient manifests as least two distinct personalities that alternately control the actions of the patient.
- In at least one of the personalities, the patient has no memory of the activities of the other personality, except those that could be explained by mere forgetfulness.
Although the condition is thought to be very common (affecting up to 3% of the population), it is very poorly studied, and both the diagnostic criteria and treatment often vary greatly from place to place or even therapist to therapist. However, the condition usually manifests itself in patients who have a long history of different psychiatric diagnoses and treatment failures. It's often associated with substance abuse, eating disorders, anxiety, Post-traumatic stress disorder, and other personality disorders.
Many psychiatrists belief the condition is merely a manifestation of borderline personality disorder and that no diagnostic criteria exist that can distinguish the two conditions.
Therapists disagree what therapy works best for patients, but there general consensus that medication is ineffective unless there is another treatable mental illness that accompanies the disorder. In addition, the symptoms can get better and worse over time even with no treatment. Suicide and other forms of self-harm are a possibility in such patients.