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Happier Young Adults May Be at Lower Risk of Dementia

November 3, 2021

Being happy as a young adult may help to protect the brain against cognitive decline and dementia later in life. But depression in young adulthood may take a toll on the brain, a new report suggests. The study found that young adults who were depressed were significantly more likely to suffer from serious memory and thinking problems in old age than their peers who were not depressed.

The findings add to growing evidence that depression can make the brain more susceptible to Alzheimer’s disease and other forms of dementia. Other studies have found links between depression and dementia in seniors, though it wasn’t clear which came first: the declining memory, or the depression. This study considered depression levels over many years, beginning in early adulthood.

For the study, researchers at the University of California, San Francisco, looked at data from about 15,000 men and women ranging in age from 20 to 89.  They divided them into three main age groups: early adulthood (under 50), middle age (50 to 69) and seniors (70 and older). All had undergone psychological screenings to test for depression. About 13 percent of the young adults had symptoms of depression, compared to 26 percent of those in middle age and 34 percent of the seniors.

Using complex statistical models, they found that those who had symptoms of depression in early adulthood were 73 percent more likely to have dementia and other cognitive problems in old age than their peers who had not been depressed. Those with symptoms of depression later in life were 43 percent more likely to have cognitive problems in old age. The findings were published in the Journal of Alzheimer’s Disease.

“Generally, we found that the greater the depressive symptoms, the lower the cognition and the faster the rates of decline,” said the study’s lead author, Willa Brenowitz, of the University of California San Francisco’s Department of Psychiatry and Behavioral Sciences. “Older adults estimated to have moderate or high depressive symptoms in early adulthood were found to experience a drop in cognition over 10 years.”

The researchers considered other risk factors for dementia, including diabetes, smoking, obesity and years of education. Being depressed was independently associated with an increased risk for dementia.

“Several mechanisms explain how depression might increase dementia risk,” said Dr. Brenowitz. “Among them is that hyperactivity of the central stress response system increases production of the stress hormones glucocorticoids, leading to damage of the hippocampus, the part of the brain essential for forming, organizing and storing new memories.”

Other studies have found links between being depressed and an increased risk of developing Alzheimer’s disease. Researchers speculate that in some people, Alzheimer’s could be a long process that begins many years, perhaps as long as two or three decades, before the actual onset of memory loss, possibly showing up as symptoms of depression in the early stages of the disease. Alternatively, it is also possible that stress hormones or other aspects of depression may in some way damage the brain, making it vulnerable to the ravages of Alzheimer’s and other forms of dementia.

Experts caution that just because you have a depression diagnosis does not mean you will develop dementia. But it may increase your risk, or it may be associated indirectly with an increased risk. It is therefore possible that getting effectively treated for depression and shortening the depressed period may lower your risk, though more research in this area is needed.

Symptoms of depression are many and varied, and include feeling sad, apathetic, worthless or hopeless; a loss of interest in daily activities; poor sleep; and trouble concentrating. If you experience these or other unusual changes in mood or behavior, consult your physician. Medications and therapeutic counseling are available that can provide relief.

By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Marc Flajolet, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.

Source: Willa D. Brenowitz, Adina Zeki Al Hazzouri, Eric Vittinghoff, et al: “Depressive Symptoms Imputed Across the Life Course Are Associated with Cognitive Impairment and Cognitive Decline.” Journal of Alzheimer’s Disease, Sept. 28, 2021

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