Definitions of depression: concordance and prediction of outcome.

Using patient samples in London hospitals, the authors compared three methods of diagnosing and subdividing depressive illness in terms of their ability to predict outcome. The Catego class D+ selected patients who continued to suffer from episodes of psychotic depression. The Research Diagnostic Criteria selected patients with schizoaffective depressions whose outcome a completely different from that of major depressive disorder. DSM-III had advantages over the other systems, since it divides depression into three subtypes that differ from each other and from schizophrenia. Patients with a DSM-III diagnosis of mood-incongruent psychotic depression had persistent schizophrenic psychopathology, but their outcome differed from that of both schizophrenic and manic-depressive patients.