Lack of stability of the RDC endogenous subtype in consecutive episodes of major depression.

The stability of the endogenous subtype of major depressive disorder was examined within individuals across consecutive episodes. The subjects were 119 probands from the NIMH Collaborative Depression Study who experienced at least two episodes of unipolar major depressive disorder within a two-year period of biannual evaluations. Structured data collection methods and Research Diagnostic Criteria were employed. The inter-episode stability of subtype diagnosis was low, never producing a kappa of greater than 0.25. This result was not attributable to threshold for diagnosis, time between episodes, differences in severity, or changes in raters.