Dissociative Identity Disorder (DID) is a severe condition in which two or more distinct identities, or personality states, are present in—and alternately take control of—an individual. The person also experiences memory loss that is too extensive to be explained by ordinary forgetfulness.
DID is a disorder characterized by identity fragmentation rather than a proliferation of separate personalities. The disturbance is not due to the direct psychological effects of a substance or of a general medical condition, yet as this once rarely reported disorder has become more common, the diagnosis has become controversial.
Some believe that because DID patients are easily hypnotized, their symptoms are iatrogenic, that is, they have arisen in response to therapists' suggestions. Brain imaging studies, however, have corroborated identity transitions in some patients. DID was called Multiple Personality Disorder until 1994, when the name was changed to reflect a better understanding of the condition—namely, that it is characterized by a fragmentation, or splintering, of identity rather than by a proliferation, or growth, of separate identities.
DID reflects a failure to integrate various aspects of identity, memory and consciousness in a single multidimensional self. Usually, a primary identity carries the individual's given name and is passive, dependent, guilty and depressed. When in control, each personality state, or alter, may be experienced as if it has a distinct history, self-image and identity. The alters' characteristics—including name, reported age and gender, vocabulary, general knowledge, and predominant mood—contrast with those of the primary identity. Certain circumstances or stressors can cause a particular alter to emerge. The various identities may deny knowledge of one another, be critical of one another or appear to be in open conflict.