PISCATAWAY, NJ – People with alcohol dependence may be more genetically susceptible to certain types of eating disorders, and vice-versa, according to a study in the September issue of the Journal of Studies on Alcohol and Drugs.
In a study of nearly 6,000 adult twins, researchers found that common genetic factors seemed to underlie both alcoholism and certain eating disorder symptoms—namely, binge eating and purging habits, such as self-induced vomiting or laxative abuse. Genes appeared to explain 38 percent to 53 percent of the risk of developing those disorders.
"This supports the idea that there are common genetic factors contributing to alcohol dependence and these eating disorder symptoms," said lead researcher Melissa Munn-Chernoff, Ph.D., of Washington University School of Medicine in St. Louis.
Past studies had shown that women who binge eat or purge have higher-than-average rates of alcohol use problems. They even have higher rates than women with other types of eating disorders. But it had not been clear whether common genes might help explain the connection.
For the new study, Munn-Chernoff's team used data from 5,993 Australian twins, both identical and fraternal. Identical twins share all of their genes, while fraternal twins share about half—making them no more genetically similar than non-twin siblings. Twin studies help researchers weed out the effects of genes from the effects of environment, including the "shared" environment twins had when growing up.
Of the adults in this study, nearly one quarter of men and 6 percent of women had ever been alcohol dependent—based on a standard diagnostic interview. Almost 11 percent of men and 13 percent of women had ever had a problem with binge eating; about 14 percent of women had ever used two or more purging tactics. (Men were not asked about purging.)
Overall, genetic susceptibility appeared key in the odds of developing any of the three disorders. What's more, it seemed some of the same genetic risk factors that made people susceptible to alcoholism also made them vulnerable to bingeing or purging.
It's not clear exactly which genes are involved. For now, the findings emphasize that alcohol dependence and these eating disorder symptoms share some common roots, according to Munn-Chernoff.
"We need to be aware that these problems can occur together, in both men and women," she said. So when health providers see someone with a drinking problem, they may want to ask about bingeing and purging symptoms, or vice-versa—something that, right now, is not routinely done, Munn-Chernoff noted.
And in general, she said, it's important to keep studying the risk factors—genetic or otherwise—for alcohol and eating disorders. "If we can better understand the risk factors, we can better understand how to treat these disorders."