Epidemiological data have long established a link between depression and Alzheimer’s disease. This study goes a little further and helps to explain this link: it identifies genetic factors common to the 2 diseases. Researchers even identify a causal role of depression in the development of Alzheimer’s disease. Dr. Aliza Wingo, of Emory University, Atlanta, one of the lead authors hypothesizes “genes that contribute to both diseases and the triggering role of depression in the development of dementia”.
This genetic link explains the epidemiological link
This is a genome-wide association study (GWAS) conducted on a very large dataset. The technique scans the entire genome for areas associated with specific conditions. Here, the analysis identifies:
- 28 brain proteins and 75 transcripts or messages that encode proteins associated with depression;
- Among these proteins and transcripts identified, 46 transcripts and 7 proteins are also found to be associated with the symptoms of Alzheimer’s disease;
- a common genetic basis for the 2 diseases, which suggests an increased risk of Alzheimer’s disease in case of depression or a history of depressive episodes.
“This large genomic analysis reveals a relationship between depression and Alzheimer’s disease and dementia at the genetic level”concludes Dr. Thomas Wingo, the other lead author of the study. “Our results explain the well-established epidemiological association between depression and an increased risk of dementia.”
Treating depression to better prevent dementia: this molecular relationship raises the question of the impact of the treatment of depression on the subsequent risk of dementia. Without being able to conclude, the authors nevertheless suggest that poorly managed depression might promote the onset of dementia without an episode of depression necessarily leading to the development of dementia later in life.
Finally, by identifying these genes common to the 2 neurological diseases, the research designates key therapeutic targets, common to the 2 diseases.
