Smoking behaviors, including the onset of smoking, smoking persistence (current smoking versus past smoking), and nicotine addiction, cluster in families. Studies of twins indicate that this clustering partly reflects genetic factors. To identify those genes that could potentially contribute to nicotine dependence scientists combined a comprehensive genome-wide scan with a more traditional approach that focuses on a limited number of candidate genes, using unrelated nicotine-dependent smokers as cases and unrelated non-dependent smokers as controls. A candidate gene has one or more variant forms, which, according to current scientific evidence, appear to be linked to a genetic disease.
“When two teenage friends experiment with smoking at the same age, one can become addicted and the other might not,” says NIDA Director Dr. Nora D. Volkow. “We want to know why. This systematic survey of the genome coupled with the ongoing identification of variants in candidate genes brings us closer to understanding what factors increase a person’s risk of transitioning from experimentation to nicotine addiction.”