Genetic Pattern of Nicotine Addiction

Scientists at the University of Iowa have discovered certain genetic profiles in smokers that may determine a person's risk of developing nicotine addiction and other psychological behaviors. Using a genome-wide scan, scientists analyzed blood samples from smokers versus nonsmokers and found similar genetic patterns among smokers that may one day be used as a genetic test to determine who may be more vulnerable to nicotine addiction.

In this latest study, published in the American Journal of Medical Genetics, Philibert and his colleagues analyzed the DNA samples of 94 people, some smokers and some nonsmokers. Using a technique called transcriptional profiling, they looked at all 30,000 genes of the human genome, fluorescently labeling those that were turned on versus those that were turned off in both groups. What they found was both promising and daunting: 579 genes were more activated and 584 other genes were less activated in smokers versus nonsmokers.

Gunter adds that few psychological behaviors exist alone. For example, people who smoke may also have panic disorders or depression, each of which may involve a number of different genes. "How do you sort that out?" Gunter asks. "Is a genetic test disorder- specific, or specific to a cluster of disorders? There may be some sites that contribute more to prediction of a disorder than other sites. In the years to come, could we prune that down? Maybe."

There's also a question of whether, once a person starts smoking, increased nicotine consumption causes certain genes to turn on or off. To that end, Philibert plans to run similar genome-wide analyses on younger people who have not yet started smoking but may have a family history of nicotine dependence. He will also analyze DNA samples from patients with single psychological diagnoses to obtain what he calls a "cleaner phenotype."

However, Hinrichs believes it will be a while before scientists can design accurate genetic tests for such disorders. "So far, researchers have identified a number of genetic markers which may increase susceptibility to drug addiction," says Hinrichs. "Any of these would only increase the risk of addiction by a small percentage. We certainly have a long way to go before we can routinely use genetic tests."