A two-dose dexamethasone suppression test in patients with psychiatric illness.

After exposure to a low and high dose dexamethasone regime, 11 of 34 acute psychiatric inpatients demonstrated abnormal dexamethasone suppression characterized by morning and/or mid-afternoon escape from suppression. This abnormality of suppression was found in primary depression, in mania, and in acute schizophrenia. In primary depression, the presence of abnormal dexamethasone suppression failed to discriminate "endogenous" depressed from "other depressed" subjects. Because nonsuppression to a high dose of dexamethasone is also found in patients with ectopic ACTH secretion and in patients with autonomous adrenal tumors, caution is necessary in the interpretation of nonsuppression which persists after recovery from psychiatric illness. As patients with Cushing's syndrome of uncertain etiology may be referred to a psychiatrist for a diagnostic evaluation, the psychological correlates of abnormal dexamethasone suppression need to be established with greater certainty.