A lifetime history of depression is associated with increased plaques and tangles in the brains of those with Alzheimer’s disease and more rapid cognitive decline, according to a study in the February issue of Archives of General Psychiatry, one of the JAMA/Archives journals.

Previous studies have linked depression and Alzheimer’s disease, according to background information in the article. People with a lifetime history of major depressive disorder (MDD) may be more likely to be diagnosed with AD. In addition, both AD and MDD are likely to affect the brain’s memory-related temporal lobes. MDD is likely to caused atrophy of the hippocampus, the area where the largest amounts of plaques and tangles form in patients with AD, the authors write.

To assess how MDD might affect the development of AD, Michael A. Rapp, M.D., Ph.D., Mount Sinai School of Medicine, New York, and colleagues compared the brains of 44 AD patients with a history of depression to those of 51 without.

The group included 32 men and 63 women with an average age at death of 81 years.

Patients with a history of depression had more tangles and plaques in the hippocampus than those without, the authors report. People who were depressed at the time they were diagnosed with AD had even more pronounced changes in their brains than those whose depression occurred earlier or later. Based on analyses of cognitive tests given during participants’ lifetimes, patients with AD who had a history of depression also experienced a more rapid decline into dementia than those who did not have depression.

“These results have great clinical significance in that the identification of potential mechanisms that link geriatric MDD as a treatable risk factor to neuropathological changes in AD may lead to the development of differential intervention and prevention strategies for AD,” the authors conclude. “Such specific interventions would be especially needed since geriatric patients with MDD with cognitive impairment may have less favorable treatment outcomes.”

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