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.

Two patients with moderately severe AD, when asked directly, could identify their own images in a mirror, but also consistently misidentified their own reflections as that of another person. Both patients were paranoid and mildy depressed at times, but had no evidence of other concurrent psychotic symptoms. It appeared that mood substantially modified the nature of the symptom and the patients' reaction to it over time. These cases illustrate the ability of an organic symptom to be modified by a concurrent affective state, indicating the importance of the interaction between biological and psychological factors in the expression of such symptoms.