Depression and Alzheimer’s Disease Share Genetic Roots

Epidemiological data have long linked depression with Alzheimer’s disease (AD), a neurodegenerative condition characterized by progressive dementia, affecting nearly 6 million Americans. A new study, published in Biological Psychiatry by Elsevier, has identified common genetic factors between depression and AD, suggesting that depression may play a causal role in the development of AD and that those with severe depression experience a faster decline in memory.

Co-senior author Aliza Wingo, MD, from Emory University School of Medicine, stated that the study raises the possibility of shared genetic contributions to both illnesses. Although the shared genetic basis is small, the findings imply a potential causal role of depression in dementia. The study utilized a genome-wide association study (GWAS), a technique that scans the entire genome for commonalities associated with specific conditions. This GWAS identified 28 brain proteins and 75 transcripts (messages that encode proteins) associated with depression. Among these, 46 transcripts and 7 proteins were also linked to AD symptoms, suggesting a shared genetic foundation that may drive the increased AD risk associated with depression.

Previous studies have examined the genetic relationship between AD and depression using GWAS, but the current work is more powerful due to larger, newly available data sets that provide more detailed information. Co-senior author Thomas Wingo, MD, emphasized that this study reveals a genetic relationship between depression and AD, which may explain the established epidemiological association between the two conditions.

Dr. A. Wingo noted that this relationship raises the question of whether treating depression could mitigate the risk of developing dementia. The study identified genes that might explain the depression-dementia relationship and merit further investigation. These genes could become important targets for treating both depression and reducing the risk of dementia.

John Krystal, MD, Editor of Biological Psychiatry, highlighted the mounting costs of ineffectively treated depression and the growing evidence that major depressive disorder increases the risk of AD. He praised the innovative study for linking genetic risk mechanisms to molecular changes in the brain, providing strong support for the hypothesis that depression plays a causal role in the biology of AD. It is important to note that having an episode of depression does not make dementia an inevitable result. Instead, the study suggests that ineffectively treated depression may aggravate the biological processes of AD, potentially accelerating the onset of symptoms and increasing the rate of functional decline.

Story Source: Materials provided by Elsevier [Link]. Content may be edited for style and length.