Sunday, September 15, 2013

Researchers Link Alcoholism and Binge Eating Behavior

Addiction and the role of genetic overlap.

More evidence has arrived, courtesy of Washington University School of Medicine in St. Louis, demonstrating a genetic link between alcoholism and binge eating disorders.

In clinical practice, it is no secret that certain binge eaters and people with bulimia also show high rates of alcoholism. Various reasons have been suggested, but one of the obvious ones is that people prone to alcoholism are also genetically susceptible to certain kinds of eating disorders. A common set of genetic factors may convey these intertwined vulnerabilities to a subset of the population.

In order to examine the matter, Dr. Melissa Munn-Chernoff and coworkers followed the time-honored route: They studied twins, both identical and fraternal, from a database of 6,000 adult twins in Australia. Twin studies have been crucial to medical understanding of comorbid disorders and addiction. In general, while alcoholism and binge/purge disorders were seen as most likely genetic in origin, it was thought that the two disorders were transmitted in families independently. Writing in the Journal of Studies on Alcohol and Drugs, the researchers conclude that “in women, some of the genetic risk factors that influenced vulnerability to alcohol dependence also influenced vulnerability to both binge eating and compensatory behaviors [purging, laxatives, diuretics].”

Previous studies cited by the researchers have pegged the individual heritabilities of alcohol dependence (50-64 percent) and bulimia (28-83%). However, the question of genetic overlap had remained relatively underexplored. Munn-Chernoff and colleagues wanted to evaluate the links between alcohol dependence and binge eating behaviors in women. Among the study group, 6 percent of women had been dependent on alcohol at some point in their lives. As for binge eating, 13% of women had experienced problems with it. 14% of women had engaged in purging or laxative abuse.

The researchers judged the genetic correlation between the two disorders to be statistically relevant: “In women, the multivariate twin model suggested that additive genetic and nonshared environmental effects influenced alcohol dependence, binge eating, and compensatory behaviors, with heritability estimates ranging from 38% to 53%.”(For the specific statistical correlations, see the full-text article. The correlation was stronger for women than for men).

In addition, the study did not find any significant shared environmental influences contributing to covariance between alcoholism and binge behaviors.

Limitations of the study include an older age cohort (mean age 44 in women), higher alcoholism rates in the Australian sample compared with the U.S., and the possibility that other comorbidities, such as depression, might influence the association.

“It appears that some genes that influence alcohol dependence also influence binge eating in men and women,” said Melissa Munn-Chernoff, in a prepared statement. “When you go to an eating disorder treatment center, they don’t often ask questions about alcoholism. And when you go for alcoholism treatment, they don’t generally ask questions about eating disorder symptoms. If centers could be aware of that and perhaps treat both problems at the same time, that would be a big help.”

Women who abuse alcohol have it tough for any number of reasons, and this study gets at one of them: “A combination of pressures to adjust to the changing body at puberty, increased access to alcohol via peer networks, and genetic predispositions for eating disorder symptoms and alcohol problems could result in comorbid alcohol dependence and bulimia symptoms."

Munn-Chernoff M.A., Duncan A.E., Grant J.D., Wade T.D., Agrawal A., Bucholz K.K., Madden P.A.F., Martin N.G. & Heath A.C.  A twin study of alcohol dependence, binge eating, and compensatory behaviors., Journal of studies on alcohol and drugs,    PMID:


Marc Lewis said...

HI Dirk. You mention depression and alcoholism as possible confounds. I suppose they are, statistically, if they haven't been measured and treated as mediating/moderating variables. But isn't this the main act?

I don't know what to do with the "alcoholism" "confound" -- Alcoholism means heavy drinking, just like eating disorder means heavy eating. Doesn't seem like a confound, but rather just another word for the same thing. But more interesting is the role of depression. Many addicts (as you and I well know) see depression as a primary cause. It wouldn't be hard to imagine that a genetic predisposition to depression is THE shared factor. Then booze and food are just two different ways to fill up the same hole.

I wonder why these ideas -- so familiar and even obvious to addicts and their loved ones -- seem not to make a dent in the minds and models of addiction researchers! That's another good argument for getting addicts and scientists to talk to each other. Or, in my case, to be the same person!

Dirk Hanson said...

Yeah, alcoholism is a typo there, obviously not a confound. Thanks for spotting that.

I think there's good reason to see a genetic predisposition that is marked by depression and impulsivity, and expresses itself as addiction to, well, anything addictive. Booze, food, crack—drug of choice is pretty secondary.

John Burns said...

Well, there are plenty of people who substitute eating with drinking, when they're trying to recover from addiction. Perhaps this is why.

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