Is depression a predictor or risk factor for Dementia?

Depression across life stages and Dementia in Denmark.


The study explores the relationship between depression and Dementia, aiming to uncover whether depression is an early indicator or a risk factor for dementia development.

Researchers from Stanford University have long known that there is a connection between depression and Dementia. However, they’re trying to figure out which one comes first. Is depression an early sign of Dementia, or can being depressed lead to developing Dementia?

Researchers have some ideas about this. One thought is that as brain cells start to get damaged, the parts of the brain linked to mood are affected. Another theory is that when people notice their memory isn’t as good as before (due to mild Dementia), they might become depressed. Some scientists also think that changes in the brain linked to mood disorders might increase the chances of developing Dementia.

A team of scientists led by Victor Henderson, MD, has worked to find answers. Their study, published in JAMA Neurology, showed that people diagnosed with depression before are more than twice as likely to get Dementia, even if their depression was many years ago.

Henderson, who directs the Farrukh-Jamal Stanford Alzheimer’s Disease Research Center, said, “The researchers are still unclear how depression increases the risk of developing dementia. But “this interval of multiple decades suggests that depression isn’t just an early manifestation of dementia.”

“In this new study, Henderson and his team worked with researchers from the University of Pennsylvania and Aarhus University in Denmark. They used an extensive collection of health records, called the Danish National Patient Registry, to look at info from over 1.4 million adults in Denmark between 1977 and 2018. They found 246,499 people who had depression, and most of them had it before they were 60 years old.

The results showed that people with depression were 2.41 times more likely to get Dementia than those without depression. It was true even if the depression was diagnosed 20 years before Dementia started. It was also true if someone had depression when they were young. Even people with depression 20 to 39 years earlier still had almost twice the risk of Dementia compared to those who never had depression.

Dr. Henderson was surprised that the link between depression and Dementia was strong even when so many years had passed. He said, “This reminds us how important mental health is and that we must take depression seriously.”

Dr. Henderson said “we need more studies to confirm these findings in other places, like the United States. Also, we need to check if treating depression can lower the chance of getting Dementia. Even though we know more about when the link happens, we still don’t fully understand why depression and Dementia are connected.”

He suggested a few ideas. Maybe people with depression don’t socialize as much and do fewer activities that keep their minds and bodies busy. There could also be genes that make people prone to depression and Dementia. Another thought is that the inflammation seen in the brains of depressed people might start processes that lead to Dementia. But researchers are not entirely sure why these two things are linked.”

In conclusion, this study sheds light on the complex relationship between depression and Dementia. While further research is needed to establish a definitive causal link, the findings suggest that depression could serve as an early warning sign or potential risk factor for the development of Dementia.

Early detection and effective management of depression may play a crucial role in reducing the overall risk of Dementia. Healthcare professionals should consider the implications of these findings in both clinical practice and public health strategies aimed at addressing cognitive decline in aging populations.

Journal Reference:

  1. Holly Elser, Erzsébet Horváth-Puhó, et al., Association of Early-, Middle-, and Late-Life Depression With Incident Dementia in a Danish Cohort. JAMA Neurology. DOI: 10.1001/jamaneurol.2023.2309.
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