People With Depression May Face a Higher Risk of Dementia

Two new studies suggest that experiencing depression early in life or midlife increases the risk and progression of memory problems and cognitive decline.

In a previous research review, scientists found that the early onset of depression, as well as the duration and frequency of depressive symptoms, were associated with a two to four times greater risk of developing dementia.

A more recent 2023 study involving 1.4 million adult Danish citizens found that people with diagnosed depression had more than double the risk of dementia. Moreover, the risk of dementia persisted whether depression was diagnosed in early, mid, or late life.


Now, the results of two new studies published on June 11 in JAMA Network Open and June 12 in Neurology, the medical journal of the American Academy of Neurology, add more weight to the growing body of evidence that mental health can impact dementia risks.

Depression and memory issues are a two-way street

In the study published on June 11 in JAMA Network Open, researchers from the University College London (UCL) found that among participants aged 50 or older, those with more depressive symptoms at the start of the study also had more memory issues and experienced more memory changes over time.

Moreover, the results showed a bidirectional effect as memory issues also appeared to accelerate depressive symptoms.

Still, the study's authors suggest that treating depression may help slow memory decline.

In a UCL press release, senior author Dr. Dorina Cadar, from the UCL Department of Behavioural Science & Health and Brighton and Sussex Medical School, said, "Depression can cause changes in brain structures, such as the hippocampus, which is critical for memory formation and retrieval. Chronic stress and high levels of cortisol associated with depression can damage neurons in these areas."

Cadar noted that more research is needed so scientists can develop targeted interventions to improve mood and slow cognitive decline in people with depression and memory impairment.

Black individuals may face greater risks


In another study, published in the June 12 online issue of Neurology, the medical journal of the American Academy of Neurology, researchers found that people who experience depression earlier in life may have challenges with thinking and memory when they reach middle age. Moreover, the association was stronger among Black individuals.

"The processes that lead to dementia begin long before signs of the disease become apparent, and previous research has shown that Black adults have a higher risk of dementia than white adults," said study author Leslie Grasset, Ph.D., from the University of Bordeaux in France, in a news release. "Our study found that prolonged exposure to elevated depressive symptoms in young adulthood has a negative effect on thinking and memory in middle age, especially for Black adults."

The study's authors point out that higher rates of depression among Black people may be due to inequalities in socioeconomic resources such as housing and access to health care and treatment. They suggest that scientists and healthcare providers should consider these disparities when designing treatments to reduce a person's risk of dementia.

Why would depression lead to memory issues?

While the studies did not prove depression causes cognitive decline or dementia, the evidence did show associations between the two conditions even after accounting for demographic factors that could interfere with the results, such as age, physical activity, and alcohol consumption.

So, the mechanisms behind the associations remain unclear.

However, in addition to the potential for depression-related stress and high cortisol levels to damage neurons, the researchers involved in the UCL study suggest that other factors may include, serotonin and dopamine imbalances, structural changes in brain areas involved in processing memory, and disruptions to the brain's ability to create new connections.

Psychological issues, including dwelling on negative feelings and emotions, could also play a role.

Other research published in 2023 suggests that chronic stress can cause inflammation in the brain and may accelerate the build-up of beta-amyloid plaque and tau tangles, two mechanisms associated with Alzheimer's disease.

In addition, the scientists involved in the 2023 study say that vitamin D deficiency — which is associated with cognitive symptoms and may be involved in mood disorders and dementia — could play a role in the links between depression and memory problems.


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