As part of an ongoing longitudinal study of the effects of nicotine metabolism on smoking trajectory, 164 adolescent (aged 13–7) smokers (smoking at least once a month, but less than 5 cigarettes a day) were recruited from San Francisco Bay area high schools and pediatric clinics using fliers and online advertising. Individuals interested in joining the study contacted study personnel via phone, e-mail, text messaging, or social media. Study staff screened interested individuals for admission criteria. We chose to focus on adolescents who smoked fewer than 5 cigarettes per day in order to capture potential increases in smoking over the duration of the three-year study.
