More Happiness Leads to Better Cognition

Many things can damage cognition. Poor diet, lack of exercise, and excessive stress are just a few. However, according to research conducted at University of California, San Francisco, less happiness in early adulthood can predispose us to developing dementia in later life.

Using innovative statistical methods to predict average trajectories of depressive symptoms for approximately 15,000 participants ages 20 to 89, researchers then divided these into three life stages: older, midlife and young adulthood. Next, they applied these predicted trajectories and found that in a group of approximately 6,000 older participants, cognitive impairment odds were 73 percent when they had elevated depressive symptoms in early adulthood, compared to 43 percent higher odds when they had elevated depressive symptoms in later life.

These results stood even when they were adjusted for depressive symptoms in other life stages and for differences in age, sex, race, educational attainment, body mass index, history of diabetes and smoking status.

“Several mechanisms explain how depression might increase dementia risk,” explains first author Willa Brenowitz, PhD, MPH, of the UCSF Department of Psychiatry and Behavioral Sciences and the Weill Institute for Neurosciences.

One avenue Brenowitz points to is hyperactivity of the central stress response system, which 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. These findings support previous studies that have linked depression with atrophy of the hippocampus.

“Generally, we found that the greater the depressive symptoms, the lower the cognition and the faster the rates of decline,” notes Brenowitz. This is particularly relevant when it is estimated that up to 20 percent of the population suffer from depression during their lifetime, and rates of depression in early life have been rising consistently.

The takeaway is that mental health and cognitive health are related investments and when we protect them early on, the payoff extends well into our later years.

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