USA Today (Society for the Advancement of Education): Compulsive Gambling May Be Inherited

Casinos, gambling boats, and state lotteries are popular ways to raise revenue and provide some excitement for those who play. As legalized gambling has become more common in the U.S., though, problems have sprung up as well. In part, that is because some people are genetically predisposed to certain gambling behaviors, according to researchers at Washington University School of Medicine in St. Louis (Mo.) and the Veterans Affairs Medical Center in St. Louis.

They studied 3,359 pairs of twins to get a better idea of genetic influences on gambling behavior. The sample included both identical twins, who have exactly the same genes, and fraternal twins, who share about half of their genes. "Because all of these twins were brought up in the same household, we can control for differences in formative experiences during youth. Those experiences will tend to be very similar, so with both identical and fraternal twins, we are able to zero in on inherited factors," explains Seth A. Eisen, associate professor of medicine at the university and a staff physician for the Department of Veterans Affairs. "By comparing the sharing of a particular behavior in identical twin pairs with that in fraternal twin pairs, we can estimate the inherited and noninherited contributions to that behavior."

To be diagnosed officially with a psychiatric condition called pathological gambling disorder, an individual must exhibit at least four of nine behaviors, which include gambling larger amounts than intended, irritability if unable to gamble, and sacrificing important activities in order to do so. "We were able to estimate the specific genetic component for two of those gambling behaviors. One was gambling larger amounts than intended, and the other was repeated efforts to reduce or stop gambling. For those two symptoms, we found that about half of the gambling behavior was genetically mediated."

For three other behaviors--attempts to win back losses at the same place, frequent preoccupation with gambling, and increased betting to maintain interest--the researchers were able to identify a familial vulnerability. That is a combination of inherited factors and environmental experiences during growth and development.

The prevalence of each gambling behavior was higher in identical than fraternal twins. If one identical twin exhibited a particular behavior, the odds were high that his or her twin would exhibit that behavior as well. The odds were lower in fraternal twin pairs, which are less similar genetically than identical twins. The researchers therefore concluded that genetic influences are an important explanation for vulnerability to many gambling behaviors.

Between one and three percent of the American population has major gambling problems, and many more people who don't meet the official criteria for pathological gambling find that betting adversely affects their lives and relationships. That negative influence is becoming more apparent as gambling is more widely available. When placing a bet meant traveling to Las Vegas or dealing with a bookmaker, people with a genetic risk for compulsive gambling had fewer difficulties. Now, it often is a matter of just heading to the nearest grocery store to buy a lottery ticket.

"It is becoming increasingly easy to gamble in the United States--particularly in the last 10 years or so--and problems with gambling are much more common now than they were previously," Eisen notes. "Presumably that's because some of us are vulnerable to becoming gamblers because of our genes and/or experiences when we were very young. With our increased access to gambling, some of us develop problems."