Adrenocortical function and depressive illness in mentally retarded patients.

The authors administered a 1-mg dexamethasone suppression test (DST) to 85 institutionalized adults with mild to profound mental retardation after screening to exclude false-positive nonsuppression. Thirty-one (36%) of these subjects had baseline hypercortisolemia, which was significantly correlated with age, symptoms, and "modified" DSM-III criteria for major depressive disorder. Twenty (24%) of the 85 subjects were nonsuppressors (5 micrograms/dl) after testing; nonsuppression was significantly related to age, female sex, level of retardation, symptoms, and "modified" DSM-III criteria for major depressive disorder (sensitivity 41%, specificity 81%). First-order partial correlations maintained significant relationships between age and severity of retardation but not sex. Mental retardation itself did not appear to invalidate the DST.