How Depression Could Lead to Cognitive Decline in Old Age

Researchers at the University of California showed that depression-related symptoms experienced in early adulthood also increase the risks of dementia.

This finding comes from research conducted to determine if poor mental health during early adulthood could cause cognition problems. The results add to other studies that link depression to dementia and suggest that being happier in early adulthood could reduce the chances of getting dementia.

Relationship Between Depression and Dementia

While conducting the research, the researchers utilized innovative statistical techniques to determine average trajectories of symptoms. Their research included around 15,000 participants aged between 20 and 89.

They divided the participants into groups of young adulthood, midlife and older. Using their predicted trajectories, the researchers found that in around 6,000 older participants, 73 percent of people who had high symptoms as young adults had cognitive impairment.

However, in older people who had experienced symptoms later in life, only 43 percent had cognitive impairment.

They adjusted the results depending on other life stages and differences in factors like race, sex, age, body mass index, smoking history, educational attainment and diabetes history.

According to Dr. Willa Brenowitz, the first author of the study, there are different ways that depression links to cognitive impairment or dementia.

Excess Stress Hormone Production

According to Dr. Willa Brenowitz, excess stress hormone production is the first and main way depression in early adulthood affects cognition.

Depression causes hyperactivity in the part of your brain that stimulates your adrenal glands to release more glucocorticoids, like cortisol, the stress hormone. Those high amounts of stress hormone later cause damage and harm to the hippocampus, which is the part of your brain that is usually responsible for creating, organizing and storing new memories plus cognitive functions.

Atrophy of the Hippocampus

The hippocampus is a part of the brain that is usually more vulnerable to health insults. According to Dr. Willa Brenowitz, people who have had depression symptoms or still have depression may have reduced hippocampal volumes.

The researcher claims that the volume loss could be due to the high levels of the stress hormone. She adds that the hippocampus is vulnerable and might get into a non-ideal state, leading to lost volume.

This research study also reveals other reasons why depression in early adulthood could cause cognitive decline, or dementia: increased inflammation, increased amyloid accumulation, factors of depressed nerve growth and vascular disease.

Research Results

According to the symptoms trajectories that the researchers used, the results formed a U-shaped curve. This curve resembled other results from age-related research studies, adding credibility to this study’s predicted trajectories.

During the study, the researchers screened their participants for depression with a 10-item questionnaire known as the CESD-10. The questionnaire helped assess symptoms among the participants for the preceding week.

They found moderate or high depressive symptoms in 34 percent of the older participants, 26 percent of the middle-aged participants, and 13 percent of the younger participants.

The researchers also found that the older adults who had high symptoms in their early adulthood showed a drop in their cognition within the first ten years, which became faster in old age.

Dr. Kristine Yaffe, the senior study author, noted that, with about 20 percent of people suffering from anxiety, it is important for people to understand the role that it plays in cognitive aging. She also added that further studies are needed to confirm the findings, but people need to prioritize screening and treatment.