Study provides more evidence linking depression to dementia risk

Older adults who have been diagnosed with severe depression have higher levels of protein deposits on the parts of their brain involved in decision-making, complex reasoning, memory and emotions than counterparts who aren’t experiencing depression, according to the results of a study published in the November issue of the Archives of General Psychiatry.

In the study, UCLA researchers used a brain scan to assess the levels of amyloid plaques and tau tangles in older adults with a type of severe depression called major depressive disorder (MDD). Previous research has suggested that plaque and tangle deposits in the brain—hallmarks of Alzheimer’s disease and many dementias—are associated not only with memory loss but also with mild symptoms of depression and anxiety in middle-aged and older individuals.

UCLA researchers have created a chemical marker called FDDNP that binds to both plaque and tangle deposits, which can then be viewed through a positron emission tomography (PET) brain scan, providing a “window into the brain.” Using this method, researchers are able to pinpoint where in the brain these abnormal protein deposits are accumulating.

“This is the first study using FDDNP to assess the abnormal protein levels in brains of older adults with severe depression,” said the study’s senior author, Dr. Gary Small, UCLA’s Parlow-Solomon Professor on Aging and a professor of psychiatry at the Semel Institute for Neuroscience and Human Behavior at UCLA. “The findings suggest that the higher protein load in critical brain regions may contribute to the development of severe depression in late life.”

Dr. Small noted that previous research has shown that depression may be a risk factor for or a precursor to memory loss, such as mild cognitive impairment, which can later lead to dementia.

“We may find that depression in the elderly may be an initial manifestation of progressive neurodegenerative disease,” said the study’s first author, Dr. Anand Kumar, the Lizzie Gilman Professor and department head of psychiatry at the University of Illinois at Chicago. “Brain scans using FDDNP allow us to take a closer look at the different types of protein deposits and track them to see how clinical symptoms develop.”

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