Multiple personalities

Dissociative identity disorder
An artist's interpretation of one person with multiple "dissociated personality states"
Classification and external resources
Specialty	Psychiatry
ICD-10	F44.8
ICD-9-CM	300.14
DiseasesDB	Comorbid
eMedicine	article/916186
MeSH	D009105
[]

Dissociative identity disorder (DID), previously known as multiple personality disorder (MPD), is a mental disorder characterized by at least two distinct and relatively enduring identities or dissociated personality states that alternately show in a person's behavior, accompanied by memory impairment for important information not explained by ordinary forgetfulness. These symptoms are not accounted for by substance abuse, seizures, other medical conditions, nor by imaginative play in children. Diagnosis is often difficult as there is considerable comorbidity with other mental disorders. Malingering should be considered if there is possible financial or forensic gain, as well as factitious disorder if help-seeking behavior is prominent.

DID is one of the most controversial psychiatric disorders, with no clear consensus on diagnostic criteria or treatment. Research on treatment efficacy has been concerned primarily with clinical approaches and case studies. Dissociative symptoms range from common lapses in attention, becoming distracted by something else, and daydreaming, to pathological dissociative disorders. No systematic, empirically supported definition of "dissociation" exists.

Although neither epidemiological surveys nor longitudinal studies have been conducted, it is generally believed that DID rarely resolves spontaneously. Symptoms are said to vary over time. In general, the prognosis is poor, especially for those with comorbid disorders. There are few systematic data on the prevalence of DID. The International Society for the Study of Trauma and Dissociation states that the prevalence is between 1 and 3% in the general population, and between 1 and 5% in inpatient groups in Europe and North America. DID is diagnosed more frequently in North America than in the rest of the world, and is diagnosed three to nine times more often in females than in males. The prevalence of DID diagnoses increased greatly in the latter half of the 20th century, along with the number of identities (often referred to as "alters") claimed by patients (increasing from an average of two or three to approximately 16). DID is also controversial within the legal system, where it has been used as a rarely successful form of the insanity defense. The 1990s showed a parallel increase in the number of court cases involving the diagnosis.

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