Researchers have identified a set of genes that may play a vital role in inducing people to kick smoking.
Researchers at Duke University Medical Center, the National Institute of Drug Abuse, University of Pennsylvania and Brown University scanned the entire human genome in a comprehensive search for genes that could determine treatment outcome.
They identified several genetic variations that seem to indicate the likelihood of success or failure of nicotine replacement therapy (NRT) and bupropion (Zyban).
"This takes us a big step forward in being able to tailor treatment to individual smokers to provide the therapies that are most likely to benefit them," said Jed Rose, Ph.D., director of Duke's Center for Nicotine and Smoking Cessation Research and one of the study's authors.
"In a few years, a simple blood test may provide physicians with enough information to recommend one treatment over another," Rose added.
In previous studies, the researchers performed the first genome-wide scan of more than 520,000 genetic markers taken from blood samples of smokers entered in a quit-smoking trial.
When they compared the genes of smokers who had successfully kicked the habit to those who failed to quit, they found clusters of positive results in gene variants present more frequently in the successful quitters.
Rose said that the current findings 'confirmed that most of the genetic markers we previously identified remain significant predictors of who will have the most likelihood of success.'
George Uhl, MD, PhD, chief of the molecular neurobiology research branch at the National Institute on Drug Abuse and lead author of the study, said that the study marks significant inroads in the study of smoking cessation.
"It helps us understand why some people are able to quit smoking more easily than others," he said.
He added that the latest findings 'provide potential clues to match individuals with treatments'.
Both therapies NRT and Zyban have proven effective at helping people abstain from smoking, but use different pharmacological mechanisms to achieve that abstinence.
In the new study, Dr Uhl's laboratory analyzed the DNA of 550 smokers entered into quit-smoking studies in which they were randomly assigned to placebo, NRT or bupropion.
Researchers assessed quit-smoking success several weeks later and found 41 gene variants specific to smokers who successfully stopped smoking using NRT, and 26 bupropion-specific genes.
"Everybody has some version of these genes, but different people have distinct variants," Rose said.
The researchers insist that the presence of these genetic variants alone is not enough to completely predict specific treatment success or failure.
Rose also warned that not enough is known, yet, about what role the genes play.
"It may be that each gene is adding its own influence. We still don't know if each gene interacts with each other or if each gene is casting its vote and we're simply counting up all the votes," Rose said.
Their findings appear in the June issue of Archives of General Psychiatry.