Dexamethasone suppression test in depression with reversible dementia.

Depression with reversible dementia occurs frequently in the elderly and may be a diagnostic problem. The 1-mg dexamethasone suppression test (DST) was performed in 175 elderly psychiatric patients. Abnormal DSTs occurred in both patients with primary degenerative dementia (n = 43, 34.9%) and those with major depression without cognitive dysfunction (n = 59, 66.1%). This finding suggests the presence of common hypothalamic abnormalities in these two disorders. There was no difference in the incidence of abnormal DSTs among depressives with a reversible dementia (n = 28, 78.6%), cognitively intact depressives (n = 59, 66.2%), and depressives who also had primary degenerative dementia (n = 24, 70.8%). An abnormal DST is not clinically useful in predicting the outcome of dementia in depressed patients with cognitive dysfunction.