Not all smokers are nicotine dependent. Among current smokers, approximately 60% are nicotine dependent based on the Fagerström Test for Nicotine Dependence, a well established scale for assessing nicotine dependence [6-7]. Dependence on nicotine has multiple underlying etiologies that include genetic predispositions and environmental risk factors. Evidence for genetic factors contributing to the risk of smoking behaviors and nicotine dependence is shown by the clustering of heavy smoking and nicotine dependence in families and the similarity of smoking behaviors in identical twins [8-9]. In contrast to nicotine dependent smokers, light, non-dependent smokers or “chippers” smoke a few cigarettes per day and can easily quit smoking [10]. These light smokers represent about 15% of the smoking population and can provide a genetic contrast group compared to heavy, nicotine dependent smokers.
