Alcohol intake and reduced brain volume: What explains the link?
Does drinking more alcohol shrink the brain, or does a smaller brain volume actually predispose individuals to drink more alcohol?
Excessive alcohol consumption carries many risks, including heart and liver problems, a higher risk of cancer, and even brain damage.
Research has suggested that there is an association between high alcohol intake and reduced white and gray matter in the brain.
So far, most specialists have maintained that alcohol consumption leads to this decrease in brain volume, but could that conclusion be wrong?
Recently, a team of investigators from Washington University in St. Louis, MO, and Duke University in Durham, NC, has conducted a study that suggests that alcohol may not be the culprit behind lower brain volume.
Instead, the findings indicate that both reduced brain volume and a predisposition toward consuming higher quantities of alcohol may have the same underlying cause: genetic makeup.
“Our results suggest that associations between alcohol consumption and reduced brain volume are attributable to shared genetic factors,” says senior author Ryan Bogdan.
“Lower brain volume in specific regions may predispose a person to greater alcohol consumption,” he goes on to note.
“The study is impressive because it uses a variety of approaches and data analysis techniques to reach findings that all converge on the same conclusion,” Bogdan also adds.
Are genes the underlying cause?
In the study — the findings of which appear in the journal Biological Psychiatry — the researchers analyzed the data from three separate brain imaging studies. These studies included one that recruited twins and non-twin siblings with different alcohol intake behaviors and one that involved children who had not had exposure to alcohol at baseline.
In the third study, the researchers had conducted analyses to determine gene expression in the brain using tissue samples that they had collected postmortem from donated organs.
In total, the investigators had access to data on 2,423 individuals. The three studies that the researchers accessed the data through were: the Duke Neurogenetics Study, the Human Connectome Project, and the Teen Alcohol Outcomes Study.
“Our study provides convergent evidence that there are genetic factors that lead to both lower gray matter volumes and increased alcohol use,” says lead author David Baranger.
More specifically, the team found that individuals who had a higher alcohol intake had lower gray matter volume in the dorsolateral prefrontal cortex and the insula, which are two brain regions that play key roles in emotion, memory retrieval, reward cycles, and decision-making.
The researchers noted that, according to their analysis, lower gray matter in these two brain regions was actually due to a specific genetic makeup, which, in turn, was also associated with an increased risk of higher alcohol consumption, both in adolescence and in young adulthood.
“These findings don’t discount the hypothesis that alcohol abuse may further reduce gray matter volumes, but it does suggest that brain volumes started out lower to begin with,” Baranger clarifies.
“As a result,” he adds, “brain volumes may also serve as useful biological markers for gene variations linked to increased vulnerability for alcohol consumption.”
In the conclusion to their study paper, the investigators note that we should, perhaps, pay more attention to genetic risk factors when assessing the risk for higher alcohol consumption.
“Taken alongside evidence that heavy alcohol consumption induces gray matter volume reductions, our data raise the intriguing possibility that genetically-conferred reductions in regional gray matter volumes may promote alcohol use from adolescence to young adulthood, which may, in turn, lead to accelerated atrophy within these and other regions.”
Moreover, the authors note that although the current findings relate specifically to alcohol consumption, they could also apply to the risk of using other substances, which the same genetic risk factors may drive.