Depression’s causal role in Alzheimer’s disease

An article in Monitor in Psychology in June 2022 addressed “Depression’s Causal Role in Alzheimer’s Disease.” Here’s the abstract:

Depression may have a causal role in Alzheimer’s disease (AD), but the reverse may not be true, suggests research in Biological Psychiatry. Researchers performed a genome-wide association study (GWAS), a technique that scans the entire genome for areas of commonality associated with specific conditions. They looked at a 2019 analysis of depression among 807, 553 individuals and a 2019 study of AD among 455, 258 individuals, all of European ancestry. The GWAS identified 28 brain proteins and 75 transcripts – the genetic messages that encode proteins – associated with depression. Among those, seven proteins and 46 transcripts were also associated AD. The data suggest the two diseases share a genetic origin, which could spur an increased risk for AD associated with depression. Assessing the effect of 115 single-nucleotide polymorphisms (SNPs) from the depression GWAS uncovered evidence that the SNPs cause depression, which in turn causes AD. The researchers conducted the same analysis on 61 SNPs from the AD GWAS but found no evidence that AD causes depression.

While I am not familiar with the methodology, the large sample size and findings are impressive. It seems to me that this may be helpful in addressing depression in people with mild symptoms of AD, rather than assuming that is the symptoms of AD that are causing the depression.