The dexamethasone suppression test in Alzheimer's disease and major depression: relationship to dementia severity, depression, and CSF monoamines.

Patients with Alzheimer's disease (AD) have been reported to have a rate of nonsuppression on the dexamethasone suppression test (DST) comparable to that of patients with major depression. With symptoms of depression being increasingly recognized in patients with AD, studying their DST response may provide clues to the etiology of the abnormal response in both diagnostic groups. A correlation between dementia severity and post-dexamethasone cortisol was found within the group of male, but not female AD patients. Within the group of elderly depressives, a correlation between post-dexamethasone cortisol and ratings of depression was found. Serum dexamethasone levels were not significantly lower in the nonsuppressors as compared with suppressors in either diagnostic group. Within the AD group, dexamethasone levels themselves correlated significantly with ratings of dementia severity and with the Wechsler Memory Scale score. Cerebrospinal fluid (CSF) 3-methoxy-4-hydroxyphenylglycol (MHPG) correlated positively with 4:00 pm post-dexamethasone cortisol level and with ratings of dementia severity in the AD patients. Findings are discussed in light of the known clinical and other biological similarities between AD and major depression, followed by a review of theories regarding the etiology of the hypothalamic-pituitary-adrenal abnormalities in these two illnesses.