UConn scientists uncover possible cause of Alzheimer's disease

New Research Reveals Key Link Between Depression and Alzheimer’s Disease

Recent studies conducted by researchers at the UConn Center on Aging have revealed a significant causal connection between depression and Alzheimer’s disease and related dementia (ADRD). This groundbreaking discovery offers new hope for developing targeted interventions to prevent or delay the onset of these conditions.

The Alzheimer’s Association estimates that over 7 million people in the United States are living with ADRD. Dr. Breno Diniz, an associate professor of psychiatry at UConn Health and the Center on Aging, has been at the forefront of this research. His work highlights how depression is associated with increased brain inflammation and a reduced ability to clear toxic proteins like amyloid-beta from the brain. These biological changes may contribute to the development of Alzheimer’s disease.

“We can now focus on creating more specific interventions to prevent Alzheimer’s in individuals who experience depression,” said Diniz. “This approach allows us to target the underlying causes rather than applying broad treatments.”

Since the 1980s, researchers have recognized that a history of depression, even during early adulthood, is one of the most significant risk factors for developing Alzheimer’s later in life. According to UConn Today, approximately 11.1% to 14.7% of ADRD cases in the U.S., affecting around one million people, are linked to major depressive disorder.

Diniz’s recent study, published in Nature Mental Health and co-authored by colleagues including Dr. George Kuchel, Dr. Chia-Ling Kuo, and Richard Fortinsky, strengthens the evidence linking depression and ADRD. For the first time, the study provides direct proof of a causal relationship between the two conditions.

“This is a major breakthrough,” said Diniz. “It gives us a clearer understanding of how depression contributes to the progression of Alzheimer’s.”

Diniz has been investigating the link between depression and ADRD for the past 15 years. His research builds on data from the United Kingdom Biobank, a large-scale study involving thousands of participants. Using a method called mendelian randomization, which helps determine the causal effects of various factors on health outcomes, Diniz and his team analyzed genetic and proteomic data.

Proteomics, the study of proteins produced by cells, and genomics, the study of DNA, were combined to develop a Proteomic Risk Score. This score can help predict an individual's likelihood of developing dementia based on their biological markers.

“We’ve established why depression increases the risk of dementia,” said Diniz. “Depression is not just a temporary low mood; it has long-term consequences that affect overall health.”

Dr. George Kuchel, director of the UConn Older Americans Independence “Pepper Center,” emphasized the importance of this research. The center aims to improve the quality of life for older adults by understanding the differences in aging processes.

“This study offers critical insights into why some individuals with depression are more likely to develop Alzheimer’s,” said Kuchel. “It could lead to better identification of those who would benefit from antidepressants or therapies targeting shared biological mechanisms.”

Kuchel also noted that while aging is a major risk factor for many chronic diseases, most older adults do not develop Alzheimer’s. However, he stressed the importance of addressing depression early, as it is a silent killer that increases the risk of other health issues.

“Depression can lead to chronic medical conditions and higher mortality rates,” said Diniz. “While treating depression with antidepressants doesn’t always reduce dementia risk, it remains the best option available.”

With this new understanding, researchers are now focusing on developing interventions that target brain inflammation and the removal of amyloid-beta proteins. These efforts could pave the way for more effective strategies to prevent or manage Alzheimer’s disease in individuals with a history of depression.