Multiple personality disorder in an intellectually disabled man: a case report.

The case of a young man with the dual diagnoses of severe intellectual handicap (IQ 30 and mental age 4 years) and Multiple Personality Disorder is presented. The intellectual handicap is probably due to hypoxia in infancy and the Multiple Personality Disorder follows prolonged physical and sexual abuse. The patient frequently switches between any of nine discrete but incompletely formed identities. Although some personalities seem more capable than others, all have similar levels of disability on testing. The diagnosis of psychiatric disorders coexistent with the intellectual handicap is hindered by the difficulty in separating psychiatric phenomena from the behavioural disturbances associated with the disability. Differential diagnosis and management are discussed.