A collaborative study of the emergence and clinical features of the major depressive syndrome of Alzheimer's disease.

OBJECTIVE: This report provides a description of the prevalence and clinical features of the major depressive syndrome of Alzheimer's disease using data derived from structured diagnostic assessments of 243 patients with probable Alzheimer's disease and 151 nondemented elderly comparison subjects.
METHOD: Subjects were characterized by a consortium of four Alzheimer's disease research centers and the Geriatric Psychiatry Branch of the National Institute of Mental Health. All sites administered the Clinical Assessment of Depression in Dementia, a structured, anchored diagnostic interview that was developed to reliably diagnose and characterize major depressive episodes in this population.
RESULTS: Despite the use of a common, reliable methodology for the assessment and diagnosis of major depressive episodes, the prevalence of major depression in Alzheimer's disease ranged widely from 22.5% to 54.4% across the recruitment sites. The prevalence of major depressive episodes among Alzheimer's disease patients in the aggregate sample exceeded that for elderly comparison subjects and reached nearly 50% among the most severely demented patients. Alzheimer's disease patients with a current major depressive episode had earlier mean ages at onset, a higher mean Hamilton Depression Rating Scale score, and were more likely to be experiencing psychotic symptoms than those who had not developed a major depressive episode. Although the major depressive episodes of Alzheimer's disease patients and nondemented elderly comparison subjects included similar numbers of depressive symptoms, patients with Alzheimer's disease were more likely to report a diminished ability to concentrate or indecisiveness and less likely to experience sleep disturbances and feelings of worthlessness or excessive guilt during their major depressive episodes. None of the clinical features of major depression differed significantly in frequency among depressed Alzheimer's disease patients with mild, moderate, or severe dementia. Concurrent psychotic symptoms progressively increased with dementia severity.
CONCLUSIONS: The high rate of major depressive episodes that occur after the onset of cognitive impairment among patients with Alzheimer's disease (the majority of whom had no premorbid history of major depression), common emergence in the early stages of dementia when symptoms of cognitive impairment are least likely to contribute to the syndromal diagnosis of major depression, and differences in the clinical presentations of the major depressive episodes of Alzheimer's disease patients and nondemented elderly comparison subjects, all support the validity of the major depressive syndrome of Alzheimer's disease. Our findings suggest that the major depressive syndrome of Alzheimer's disease may be among the most common mood disorders of older adults.