Case report of a person with Down's syndrome and multiple personality disorder.

A case is presented of an individual with Down's syndrome and multiple personality disorder. No such cases were found in a review of the literature. Three other individuals with Down's syndrome are also discussed whose symptoms range from experiencing imaginary friends to experiencing borderline multiple personality disorder. In all these cases the imaginary friends became more evident and resistive of diversion as the levels of stress increased. We speculate that experiencing imaginary friends progresses to experiencing multiple personality disorder in some individuals as personal stress increases. These cases also indicate that limited cognitive development does not preclude individuals from presenting with imaginary friends or multiple personality disorder.