Dissociative Identity Disorder (DID, formerly known as multiple personality disorder, or MPD) is, according to the current Diagnostic and Statistical Manual (American Psychiatric Association. & American Psychiatric Association. Task Force on DSM-IV., 2000) defined by the presence of two or more distinct identities that recurrently take control of an individual. Moreover, the disorder is characterized by some degree of psychogenic or psychological amnesia. Other symptoms include depersonalization, derealization, memory problems, and identity alteration (Gleaves, 2010). The diagnostic criteria for DID are far from clear cut and some researchers have suggested that DID is not a mental disorder at all but rather the symptom of other mental disorders such as PTSD. The other controversy is related to the DID's etiology, which to date is unclear. I personally think that diagnosing DID is very complex and that in many cases a false-positive diagnosis is given, as other underlying disorders might be present.
There are many possible causes for amnesia. Some of the causes cited in research literature are drug use, emotional trauma, PTSD (King, 2008), brain injury (Alexander, 1995), or the use of analgesics (Kemp, Agostinis, House, & Coughlan, 2010). Ruff and colleagues (2009) have pointed out that false-negative diagnoses for amnesia are common in patients with mild brain injury, as some patients have no memory of the accident but are fully oriented by the time medical personnel arrives. Accordingly, one of the key tasks of diagnosis is finding out what the patient actually remembers. This and assessing possible other causes, as outlined above, is key to accurate diagnosis. To date, there are no effective treatment options for amnesia.
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