Many DID patients have been misdiagnosed as schizophrenics and treated with neuroleptics.

Undiagnosed DID patients received incorrect diagnoses of schizophrenia in 25% to 40% of cases in two large series (Putnam, 1989; Ross, 1989), while in one stores 12% and in the other 16% had received electroconvulsive therapy.

Patients with DID or other dissociative disorders may be misdiagnosed as Schizophrenics on account of their auditory hallucinations, distrust, feelings of depersonalization, and on the MMPI (Kluft, 1987; Spiegel & Fink, 1979; Steingard & Frankel, 1985).

Interestingly, the patients who presented to me self-diagnosed [with Dissociative Identity Disorder had tried to tell previous therapists of their plight, but had been disbelieved. These therapists had used fallacious "capricious criteria" (KIuft, 1988) to discredit the diagnosis; e.g., that the patient could not possibly have MPD because she was aware of the other alters [sic!].

Research has also revealed that women who have developed PTSD in relation to early childhood sexual abuse often develop borderline personality disorder. Some severe cases will result in the development of dissociative identity disorder or depersonalization disorder. Patients who have been exposed to protracted and repeated sexual abuse may also develop schizophrenia simultaneously with PTSD.

...the vast majority of these [dissociative identity disorder] patients have subtle presentations characterized by a mixture of dissociative and PTSD symptoms embedded with other symptoms, such as posttraumatic depression, substance abuse, somatoform symptoms, eating disorders, and self-destructive and impulsive behaviors.2,10
A history of multiple treatment providers, hospitalizations, and good medication trials, many of which result in only partial or no benefit, is often an indicator of dissociative identity disorder or another form of complex PTSD.