Dual personality

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. These states 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 or other medical conditions, nor by imaginative play in children. Dissociative symptoms range from common lapses in attention, becoming distracted by something else, and daydreaming, to pathological dissociative disorders. Symptoms vary over time.

Dissociative disorders including DID have been attributed to disruptions in memory caused by trauma or other forms of stress. Research on this hypothesis has been characterized by poor methodology. An alternative hypothesis is that DID is as a by-product of techniques employed by some therapists, especially those using hypnosis, and disagreement between the two positions is characterized by intense debate. DID is one of the most controversial psychiatric disorders, with no clear consensus on diagnostic criteria or treatment. No systematic, empirically supported definition of "dissociation" exists. Diagnosis is often difficult as it is frequently associated 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.

It is generally believed that DID rarely resolves spontaneously. In general, the prognosis is poor, especially for those with comorbid disorders. There is little systematic data on rates of the condition. It is believed to affect between 1 and 3% of 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. Rates of diagnoses increased greatly in the latter half of the 20th century, along with the number of identities (often referred to as "alters") claimed by people (increasing from an average of two or three to approximately 16).

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