The research diagnostic criteria for endogenous depression and the dexamethasone suppression test: a discriminant function analysis.

Most studies examining the validity of the Research Diagnostic Criteria (RDC) for endogenous depression have been negative. RDC endogenous subtyping is not associated with short- or long-term treatment outcome, family history of affective disorder, or premorbid personality disorder. Studies examining its relationship to the dexamethasone suppression test (DST) are mixed; half report a significant association, and half do not. The RDC endogenous diagnosis may lack validity either because the criteria do not represent, or are not specific to, the endogenous subtype, or the diagnostic algorithm is inappropriate. In the present study, we conduct a discriminant function analysis on the 10 criteria for the endogenous subtype using DST results as the independent variable. We constructed a new diagnostic algorithm and cross-validated it on a second patient sample. In both samples the discriminant function classification was significantly associated with DST results, whereas the RDC algorithm was not.