In the last two decades interest in Dissociative Identity Disorder (DID), formerly known as Multiple Personality Disorder (MPD), has increased rapidly, particularly in the United States yet it is not a new subject within psychiatry. The phenomenon of multiple personalities or dissociative identities has been documented intermittently for the past two hundred years. In the eighteenth century, this phenomenon was diagnosed and researched, but in the nineteenth century, it fell into oblivion.
The history and documentation of MPD/DID suggest that there is a long-standing focus on this diagnosis associated with long-standing confusion. There has been a lack of clarity in both defining and understanding DID. The rise and fall in the popularity of this diagnosis are the results of historical and contemporary critiques that even dispute the existence of the dissociative identity or multiple personality phenomena. The questions range from philosophical issues, such as the possibility of one person having multiple personalities, to claims that childhood sexual abuse is the primary cause of this disorder.
One long-standing critique questions the existence of different alters in the patient. The term alters is defined in the literature as states exhibited by a person that appear as separate and distinct personalities. The symptoms associated with the disorder are intrusive and recurrent cognitions connected to the traumatic event or stimulus, flashbacks, sleep difficulties, irritability, difficulty concentrating, active behavioral avoidance of stimuli related to the traumatic event, and psychological distress associated with expose to stimuli or symbols related to the traumatic stressor or event. Secondary trauma has been documented previously and can be seen, for example, in situations where parents who are war veterans pass on trauma-like responses to their children.