How depression and Alzheimer’s connect in aging brains

The majority of studies that deal with Alzheimer’s look at people who either have few symptoms of cognitive decline — but who show biological evidence of the disease — or have already been diagnosed, with an eye toward how to prevent further decline.

But a new study by Massachusetts General Hospital is researching a surprising connection: the link between depression and amyloid, a protein that is said to indicate dementia.

“Our research found that even modest levels of brain amyloid deposition can impact the relationship between depression symptoms and cognitive abilities,” says Jennifer Gatchel, MD, PhD, of the MGH Division of Geriatric Psychiatry, and lead author of the study.

Gatchel is using neuroimaging, cognitive testing, clinical assessments, and routine interactions to gather information on the relationship between mood and dementia.

The study looked at seven years of data from 276 older adults who were a part of the Harvard Aging Brain Study and lived in a community. Gatchel studied two brain proteins, amyloid and tau, over a period of time to see how the changes of these compounds in the brain mapped to their clinical changes. 

“Our findings offer evidence that in healthy older adults, depression symptoms together with brain amyloid may be associated with early changes in memory and in thinking,” explains Gatchel.

“Depression symptoms themselves may be among the early changes in the preclinical stages of dementia syndromes. Just as importantly, these stages represent a clinical window of opportunity for closely monitoring at-risk individuals, and for potentially introducing interventions to prevent or slow cognitive decline.”

But Gatchel says that the relationship between depression and Alzheimer’s is a complex one, something similar to the “What came first, the chicken or the egg?” question.

Symptoms of depression may be an early sign of dementia, but recurring depression could be a risk factor of dementia. And older adults who are diagnosed with Alzheimer’s may experience a subsequent depression. 

Ultimately, Gatchel’s hope is to conduct further research on another group of older adults with more severe psychiatric symptoms to eventually improve brain health for older patients.