Neuroendocrinological and neurophysiological studies in major depressive disorders: are there biological markers for the endogenous subtype?

The possibility of characterizing subgroups of depressive disorders by biological markers was studied by means of the dexamethasone suppression test (DST), the 24-hr urinary free cortisol (UFC), the growth hormone response to the insulin tolerance test (ITT), and polygraphic sleep recordings. Forty-five hospitalized patients suffering from a moderate to severe nonpsychotic major depressive disorder were clinically subdivided into three groups: endogenous (n = 20), neurotic (n = 19), and "ambiguous" (n = 6). These clinical diagnoses were supplemented by operational diagnostic tools, namely, the Research Diagnostic Criteria (RDC) and the Newcastle Scale. The different diagnostic procedures exhibited a high degree of correspondence. Whereas the results of the ITT were normal in almost all patients, 20% of all patients were dexamethasone nonsuppressors and more than half of the patients showed a shortened REM latency. Both markers did not reveal any specificity for the endogenous subtype. A significant influence of weight loss on the DST and the excretion of UFC was evident.