Recent research on multiple personality disorder.

The last decade has seen the emergence of solid research on MPD and the dissociative disorders, particularly in the area of diagnosis and clinical phenomenology. A number of other areas have been opened up or advanced considerably. The most notable of these include child and adolescent dissociative disorders; investigation of dissociative memory disturbances; studies of differential alter personality psychophysiology and switching; cross-cultural comparisons of MPD, possession, and dissociative states; and the contribution of pathologic dissociation to the symptomatology of other psychiatric disorders. Yet to be attempted, however, are prospective clinical trials and treatment outcome studies. In addition to clinical and theoretical insights, recent research provides strong evidence for the validity of the diagnosis of MPD. The repeated replication of a core clinical phenomenology demonstrates a construct validity equal to or superior to that demonstrated for most DSM-III/IIIR disorders. The ability of several independently developed instruments to blindly discriminate MPD patients from nondissociative disorder patients with high rates of accuracy supports both the construct and discriminant validity of the diagnosis; and as the astute clinical observations of the last century continue to be confirmed, MPD manifests an historical validity absent in most modern era diagnoses. In the future, arguments about the "reality" of MPD cannot confine themselves merely to attacking one aspect of the disorder but rather must confront the broad range of evidence supporting the validity and reliability of the diagnosis. The future belongs to multicenter studies, although intensive single-case and personal-case series will continue to make important contributions in some areas. The essential elements necessary to begin prospective multicenter studies are rapidly coming together. Already one multicenter structured interview study of clinical phenomenology has been completed and other studies are underway or near publication. As these collaborative research networks mature, even more ambitious studies will be attempted. Adequate funding remains the principal obstacle and must be creatively addressed in this era of budgetary shortfalls, particularly as several research networks cross international boundaries. Exceptionally gratifying is the burgeoning interest of large numbers of psychiatric residents and psychology graduate students in the dissociative disorders. Thanks to a decade of hard work, the next generation of clinicians and researchers will know a great deal more about these patients than the last.