African Americans and European-American women with a certain gene combination are protected from alcohol use disorder even if they grew up in difficult environments — something that typically increases risk of alcoholism, according to a new study by researchers from Yale and University of Pennsylvania.
But this relationship does not hold for European-American men, meaning that childhood trauma will contribute to excessive alcohol consumption at roughly the same rate regardless of the presence of a gene combination that protects against alcoholism in other groups.
“The idea is that under certain environments, genetic risk may be more or less likely to be expressed,” said Carolyn Sartor, the principal author of the study and assistant professor of psychology at Yale School of Medicine. “Childhood adversity has been a well-documented risk factor for alcohol-related problems as well as other psychiatric outcomes, so under those conditions you may see a different expression of genetic risk.”
The study was based on blood samples from more than 4,000 Americans across the country who participated in six-hour interviews about their medical history and lifestyle, said Henry Kranzler, professor of psychiatry at the University of Pennsylvania Perelman School of Medicine. Genetic information from the sample was harvested and genotyped, or examined and compared, so that researchers could consider specific gene alleles and sequences in the context of the answers the respective subjects gave.
All of these participants mentioned early childhood trauma in their interviews, ranging from sexual abuse to violence to extreme neglect. Participants were asked about the greatest number of drinks they had consumed over the course of a day — though answers were capped at 50 to avoid exaggeration, according to the study. Another factor used was a rating of dependence and abuse of alcohol determined during the survey. Answers by participants with the relevant alleles were compared to those without the protective gene combination in order to see the relationship between the genes and the environment. This relationship varied across races and genders.
“In the presence of childhood adverse events, a normally protective allele, ADH1B, is not protective in European American men,” Kranzler said.
The ADH1B gene is involved with the metabolism of alcohol. Along with another related gene, ADH1B helps clear the body of alcohol, leading to fewer adverse effects related to drinking and in general, protects against overconsumption and alcoholism, according to the study. This pair of genes is present in about 40 percent of Asians and between 20 percent and 40 percent of Israeli Jews.
Genes, however, can be expressed differently based on the surrounding environment a person may grow up in. The two genes typically combine to help prevent misuse of alcohol, but the combination may work differently in people with traumatic childhoods, the study claims. This study in particular sought to further establish this relationship in European Americans and African Americans, as the only prior study in this line of research focused solely on Israeli-Jewish citizens.
The study also found a strong difference between men and women in the prevalence of alcohol use as well as childhood trauma. Men consumed significantly more alcohol. On average, they had eight more drinks than women as their maximum daily consumption — 24 on average as opposed to 16 drinks in a day. Women, however, experienced significantly more childhood trauma than men did.
The study further outlined the importance of strong early-childhood treatment in order to prevent widespread development of alcohol-related disorders, Sartor said. By ensuring less traumatic childhoods for more people, she says, it may be possible to reduce the prevalence of harmful alcohol use.
According to the Centers for Disease Control and Prevention, 16,749 people died in America from alcoholic liver disease in 2011.