Neuropathologic Correlates of Late-Onset Major Depression: Preclinical Research

Late life major depression (LLMD) is frequently associated with cognitive impairment, and increases the risk for subsequent dementia. Cerebrovascular disease, Alzheimer's disease (AD), and dementia with Lewy bodies (DLB) have all been hypothesized to contribute to this increased risk, though prospective studies have yet to examine these hypotheses with autopsy confirmation of the clinical diagnoses. The aim of this study is to examine the rates of cerebrovascular, AD, and DLB pathology among the first 10 participants in an LLMD brain tissue donation program. Subjects' psychiatric diagnoses and cognitive status were prospectively determined during their participation in clinical research protocols of the Intervention Research Center for Late Life Mood Disorders. After death, final clinical diagnoses were made using all clinical information, while blind to neuropathologic diagnoses. Neuropathologic assessments were conducted blind to final clinical diagnoses. Rates of neuropathology were compared with those in a cohort of subjects with dementia, without a history of LLMD, participating in an Alzheimer Disease Research Center. Seven (70%) subjects had evidence of onset of a dementia prior to death. LLMD with dementia was significantly associated with a neuropathologic diagnosis of AD. Cerebrovascular disease and DLB pathology were also frequent in the LLMD subjects with dementia, and were found in an LLMD subject without dementia. Rates of AD, DLB, and cerebrovascular disease were similar to those in the comparison subjects. These preliminary findings suggest that AD is the predominant neuropathologic condition in LLMD subjects with dementia. Further assessment of the role of comorbid cerebrovascular disease and comorbid DLB is needed.