Are schizophrenia and affective disorder related?: the problem of schizoaffective disorder and the discrimination of the psychoses by signs and symptoms.

Schizophrenia and affective disorder are separately classified. Schizoaffective disorder has been considered a variant of these, or representing several diseases. Some hypothesize a psychosis continuum. One test of these contrasting views involves discriminating the psychoses by their classic symptoms. We used discriminant function analyses to assess the ability of systematically recorded psychopathology to distinguish 167 DSM-III schizophrenics from 74 affectives. We divided the schizophrenics into chronic and schizoaffective subgroups. We discriminated chronic schizophrenics from affectives, but schizoaffectives overlapped both groups. Schizoaffective/unipolars were like chronic schizophrenics, and schizoaffective/bipolars were like affectives. However, these discriminations also substantially overlapped, and among non-affective positive features formal thought disorder was best at discrimination. Our findings do not fully support the present classification system, and suggest that its emphasis on hallucinations and delusions is overvalued.