Effectiveness of treatment for dissociative identity disorder

In a recent study by Ellason and Ross, patients with Dissociative Identity Disorder reported a decrease in symptoms on the Millon Clinical Multiaxial Inventory-II over a 2-yr. follow-up period. Patients judged to have achieved integration of their personalities rated themselves as more substantially improved on the Millon-II than did patients judged not to have achieved integration. Ellason and Ross suggested that this improvement reflected the influence of treatment; however, for several reasons, their findings are open to alternative interpretations. First, in the absence of proper control conditions, one cannot rule out the contribution of other factors to the over-all improvement of patients such as regression of symptoms toward the mean following the initial assessment. Second, patients self-reported improvement was less substantial when data were reanalyzed using more appropriate statistical criteria. Third, the greater improvement observed among integrated patients relative to nonintegrated patients may reflect influences other than differential responsiveness to treatment, such as less severe pathology prior to treatment. More systematic research is needed to clarify the effect of treatment on Dissociative Identity Disorder.