An international team of researchers has found shared genetic underpinnings for alcoholism and several psychiatric disorders including depression, ADHD and schizophrenia.
It is the largest genome-wide association study ever done on individuals with diagnosed alcohol dependency. The study led by researchers at Harvard Medical School, Yale, Indiana University, and Washington University, also bolsters other research that has shown shared genetic influences between substance abuse and certain psychiatric disorders.
“The current estimate is that one in eight Americans suffers from alcohol dependence,” said senior author Arpana Agrawal, PhD, a professor of psychiatry at Washington University School of Medicine in St. Louis. “And the gene we identified has a protective effect, but by no means is it the only thing affecting risk of alcohol dependence. We know environmental factors also play a role. We also think the genetic susceptibility to alcohol dependence stems from the small, cumulative effects of a very large number of variants across the genome.”
Along with the genome-wide association study — that included data from more than 50,000 people — this study, using data from 23andMe, also looked at the genetic correlation between alcohol dependence and 42 different traits. Those traits were as varied as nicotine addiction, major depressive disorder, BMI, and educational attainment to name a few.
But this new study, published in the journal Nature Neuroscience, is unique in that the researchers included data from individuals who were diagnosed for alcohol dependency, and the study included individuals with non-European ancestry. The researchers noted that many genes influence alcohol dependence, but genes that affect how individuals metabolize alcohol play an outsized role. Researchers found that different genetic variants were more important for people with African American ancestry versus those of European descent.
Together the findings offer more insight into the causes of alcohol dependence, a major public health issue. Worldwide alcohol abuse accounts for about 5 percent of the global disease burden, and it is tied to one in 20 deaths, according to the World Health Organization.
This study also follows on the heels of a series of studies that have explicitly looked at alcohol use, including both casual consumption and much heavier alcohol use. Both studies found distinct genetic differences between occasional consumption and alcohol abuse. For example, researchers in both studies found that there was a negative correlation between the heavy drinking associated with alcoholism and educational attainment — the number of years of formal education. But there is a positive correlation between educational attainment and more casual or social drinking.
This study, and others, suggest that social drinking is not associated with depression, but problem drinking and alcoholism are. The study also found correlations with smoking, marijuana use, and measures for lower impulse control and higher tolerance for risk taking.
The work in linking these kinds of behavioral traits and psychiatric disorders has been made possible, in large part, because researchers have been able to leverage the massive amounts of de-identified aggregate data from 23andMe, the UK Biobank and several smaller research cohorts. This study also benefited from using data from individuals who were diagnosed with alcohol dependence, but an even larger study could yield more results, the researchers said.