Major depressive episode and low dose dexamethasone suppression test.

The authors studied the validity of a low dose (0.5 mg) dexamethasone suppression test (DST) in identifying depression. Nine patients who met the criteria of major depressive episode (MDE) in the Diagnostic and Statistical Manual of Mental Disorders, another nine psychiatric patients and one normal subject underwent the DST. At least one of the two blood samples obtained either at 8 a.m. or at 2 p.m. from each of the nine patients with MDE showed a cortisol concentration of over 5.0 micrograms/dl, while the cortisol concentration in the other 10 subjects was uniformly suppressed under this level. All the patients with MDE could be identified by nonsuppression of the cortisol secretion at 8 a.m. or at 2 p.m. An "early escape" phenomenon in depressed patients reported by Carroll et al. (1976) was absent in a 0.5 mg DST, and the blood samples at 8 p.m. were less useful for identifying the depressive patient. The reason why the one point sampling method used by previous investigators was insufficient to identify the depressed patient was discussed.