"This study builds on our knowledge of genetic vulnerability to nicotine dependence, and will help us tailor smoking cessation strategies accordingly," said Dr. Nora D. Volkow, director of the National Institute on Drug Abuse in Bethesda, MD.

"It also highlights the potential value of genetic screening in helping to identify individuals early on and reduce their risk for tobacco addiction and its related negative health consequences."

The study, published in the American Journal of Psychiatry, found that quitting smokers with a specific gene cluster linked to nicotine dependence have a two-year delay in the median time it takes people to stop smoking.

"We found that the effects of smoking cessation medications depend on a person's genes," said lead author Dr. Li-Shiun Chen from the Washington University School of Medicine.

"If smokers have the risk genes, they don't quit easily on their own and will benefit greatly from the medications. If smokers don't have the risk genes, they are likely to quit successfully without the help of medications."