Depression may be associated with a higher risk of Alzheimer’s disease (AD), according to a study conducted last year.
The peer-reviewed study, which was published in the journal Biological Psychiatry in December, states that while the "mechanisms underlying this association remain unclear," they found that depression has a part to play in memory loss through Mendelian randomization, which is a method using measured variation in genes to interrogate the exposure's effect on an outcome. However, on the flip side, researchers were unable to find evidence of any role of AD causing depression.
“It raises the possibility that there are genes that contribute to both illnesses. While the shared genetic basis is small, the findings suggest a potential causal role of depression on dementia,” said co-author Aliza Wingo, MD.
28 brain proteins were also found to have been regulated by the depression genome. Of those identified, seven proteins were associated with rates of cognitive decline over time, as well as diagnosis and pathologies of Alzheimer's.
“This study reveals a relationship between depression and Alzheimer’s disease and related dementia at the genetic level,” said co-senior author Thomas Wingo, MD. “This is important because it may explain, at least in part, the well-established epidemiologic association between depression and higher risk for dementia.”
In addition, researchers also found that a higher polygenic risk score of depression is connected with a more rapid decline of episodic memory as time passes. A polygenic risk score, according to the CDC, is a way to provide a measure of your disease risk due to your genes.
The authors of the study stress that should one undergo depression for an extended period, does not imply that they will experience dementia, but rather untreated depression can aggravate AD biology.