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.