Genes make difference if quitting smoking LOUIS, May 30 (UPI) -- Genetics can predict success of smoking cessation and whether a person is likely to respond to drugs for nicotine addiction, U.S. researchers say. "We found that the effects of smoking cessation medications depend on a person's genes," first author Dr. Li-Shiun Chen of the Washington University School of Medicine in St. Louis, said in a statement. The research focused on specific variations in a cluster of nicotinic receptor genes, CHRNA5-CHRNA3-CHRNB4, which prior studies have shown contribute to nicotine dependence and heavy smoking, Chen said. The researchers used data from the National Heart Lung and Blood Institute and showed that individuals carrying the high-risk form of this gene cluster reported a two-year delay in the median quit age compared to those with the low-risk genes. This delay was attributable to a pattern of heavier smoking among those with the high risk gene cluster. The researchers then conducted a clinical trial, which confirmed that persons with the high-risk genes were more likely to fail in their quit attempts compared to those with the low-risk genes when treated with placebo. However, medications approved for nicotine cessation -- such as nicotine replacement therapies or bupropion -- increased the likelihood of abstinence in the high risk groups. In addition, those with the highest risk had a three-fold increase in their odds of being abstinent at the end of active treatment compared to placebo, indicating that these medications may be particularly beneficial for this population. The study was published in the American Journal of Psychiatry.