Variability in the application of contemporary diagnostic criteria: endogenous depression as an example.

Specified diagnostic criteria have been credited, in part, with improving diagnostic reliability. The authors hypothesize that nonuniform application of these criteria across different research centers has been one factor responsible for the failure to replicate research findings. For example, researchers using a narrow interpretation of the Research Diagnostic Criteria (RDC) have found a highly significant association between endogenous depression and a positive dexamethasone suppression test result, whereas researchers using a broad interpretation have failed to find the predicted relationship. The authors used two interpretations of the RDC and DSM-III endogenous/melancholia criteria to diagnose 60 depressed patients and found significant difference in rates of diagnoses and symptoms.