Twenty adolescent smokers were recruited from several San Francisco Bay area schools and pediatric clinics area using fliers and posters from 2006–2007. Participants were required to be between 13 and 17 years-old, and smoke between 1 and 6 cigarettes daily for at least 6 months. We chose to focus on adolescent smokers because it is in this group that the transition from social to pharmacologic smoking is most likely to occur (18). We chose to focus on lighter adolescent smokers because the stage of smoking in which adolescents are smoking 5 or fewer cigarettes per day appears to be a crucial time for studying development of nicotine addiction in teens. It has been hypothesized that this is the stage for transitioning from social smoking to early addiction (19). In addition, our previous research indicated adolescents reach a saliva cotinine concentration plateau around 5 cigarettes per day (20); suggesting that within the range of 1 to 5 cigarettes per day adolescents experience progressively increasing exposure to nicotine, whereas above 5 cigarettes per day smokers have reached a level of desired nicotine
