Tobacco use is the single largest cause of preventable morbidity and early mortality, both nationally and worldwide [1,101]. More people are addicted to nicotine, the active ingredient in tobacco, than to any other drug of abuse [2]. Owing to increasing tobacco use in developing nations, it is predicted that the annual number of worldwide deaths attributable to tobacco use will rise to more than 10 million per year by 2020. In the USA, 21% of adults were current smokers in 2005, with 24% of men and 18% of women smoking [3]. Each year, approximately 440,000 people die of a smoking-related illness [4]. The economic burden of smoking is correspondingly elevated. Although the prevalence of cigarette smoking has decreased over the last 30 years prompted by antismoking campaigns and smoking cessation programs, the decrease in smoking among adults has slowed since the mid-1990’s, highlighting the limitations of current treatments for smoking. In addition, adolescents and young adults continue to initiate cigarette use, with 21% of 16–17-year-olds and 36% of 18–20-year-olds reporting cigarette smoking in the last month [5]. The initiation of smoking occurs with the experimentation and use of cigarettes. As a person passes the threshold of 100 cigarettes smoked over their lifetime, he or she becomes a ‘smoker’, a commonly used definition that has been employed in many large-scale epidemiological studies. A range of smoking behaviors is seen among smokers, from ‘chippers’, or lowlevel smokers, who do not have symptoms of dependence, to heavy, nicotine-dependent smokers [6]. Importantly, nicotine dependence is a strong predictor of failed smoking cessation [7]. Multiple factors contribute to the transition