Study discovers common genetic factors between depression and Alzheimer’s disease

Epidemiological data have long associated depression with Alzheimer’s disease (AD), a neurodegenerative disorder identified by progressive dementia that is affecting around six million Americans. Recent research discovered common genetic factors between depression and AD.

The scientists identified that depression played a contributory role in the development of AD, and people with worse depression had quicker memory decline. The research was reported in Biological Psychiatry, published by Elsevier.

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.”

Dr Aliza Wingo MD, Study Co-Senior Author, Emory University School of Medicine

The researchers carried out a genome-wide association study (GWAS), a technique used to scan a complete genome for commonality areas linked with specific conditions. The GWAS found 28 brain proteins and 75 transcripts, which are the messages encoding proteins that were found to be linked with depression.

Among those, 7 proteins and 46 transcripts were also linked with AD symptoms. The information shows that the two diseases share a genetic basis, which might drive the enhanced risk for AD linked with depression.

Despite the fact that previous studies had analyzed AD and depression with GWAS, the present study was made more potential with the use of larger, recently available data sets that presented more detailed information.

This study reveals a relationship between depression and Alzheimer’s disease and related dementia at the genetic level. This is important because it may explain, at least in part, the well-established epidemiologic association between depression and higher risk for dementia.”

Dr Thomas Wingo MD, Study Co-Senior Author, Emory University School of Medicine

“This relationship raises the question of whether treatment of depression can mitigate the risk for dementia. We identified genes that may explain the relationship between depression and dementia here that merit further study. Such genes may be important treatment targets for both depression and reduction of dementia risk,” added Dr A. Wingo.

The costs of ineffectively treated depression continue to mount. There has been increasing evidence that major depressive disorder increases the risk for Alzheimer’s disease, but little insight into this relationship. This innovative study, which links genetic risk mechanisms to molecular changes in the brain, provides the clearest link to date supporting the hypothesis that depression plays a causal role in the biology of Alzheimer’s disease.

John Krystal MD, Editor, Biological Psychiatry

John Krystal adds, “This does not mean that if one has an episode of depression that dementia is an inevitable result. Instead, it suggests that ineffectively treated depression may aggravate the biology of Alzheimer’s disease, potentially hastening the onset of symptoms and increasing the rate of functional decline.”