Toward the validation of RDC schizoaffective disorder.

The Research Diagnostic Criteria (RDC) for schizoaffective disorder were applied to a clinic population of 71 patients with bipolar I disorder. Twenty-five patients were found to meet RDC criteria for schizoaffective disorder. The RDC-positive group were found to be the most psychotic patients and had a younger age at onset and admission to the clinic that the RDC-negative group. They had also had their conditions diagnosed more frequently as schizophrenic by referring physicians. There was no difference, however, between the two groups on many other variables, including clinical, family history, drug response, and laboratory studies. We conclude that our bipolar I population cannot be further subdivided into meaningful clinical entities using the RDC criteria for schizoaffective disorder.