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Dissociative Identity Disorder (DID), previously known as multiple personality disorder (MPD), is a mental disorder characterized by the maintenance of at least two distinct and relatively enduring personality states. This is accompanied by memory gaps beyond what would be explained by ordinary forgetfulness. The personalities alternately show in a person's behavior; presentations, however, are variable. Other problems that often occur in people with DID include borderline personality disorder (BPD), posttraumatic stress disorder (PTSD), depression, substance use disorders, self-harm, and anxiety.