Schizophrenia and affective disorder--distinct entities or continuum?: an analysis based on a prospective 6-year follow-up.

The purpose of this study was to determine whether the preponderance of data support a continuum hypothesis of the psychoses or a concept of separate, autonomous illnesses. Patients (N = 70) were hospitalized for nonmanic psychoses, given structured interviews and a dexamethasone suppression test (DST), and diagnosed according to the Research Diagnostic Criteria (RDC). Patients were then evaluated at 1 year and 6 years with a structured interview. Diagnoses were made at three points of time: intake, 1 year, and 6 years. The patients were divided into groups that had a consistent (over the three points) set of affective disorder diagnoses (affective disorder or schizoaffective disorder, mainly affective [AD group]) and those that had a consistent set of schizophrenic diagnoses (schizophrenic or schizoaffective disorder, mainly schizophrenic [S group]). A third group (inconsistently diagnosed) consisted of subjects who at one point were diagnosed in the AD group and at another in the S group. A series of discriminant function analyses suggested that the AD group differs widely from the S group; and the inconsistently diagnosed group most closely resembled the AD group. The family background of the inconsistent group was similar to that of the AD group. The DST and outcome showed that the inconsistent group was more like the AD group than the S group. Using the characteristics of the medical model-clinical picture, outcome, laboratory tests, and family history-the group that was inconsistent with regard to diagnosis over time appeared similar to the AD group. Taking the follow-up evaluation into account, the data favor the possibility that patients who have a variable clinical diagnosis over time do not suffer from schizophrenia.