Tobacco use usually begins during adolescence; over 90% of those who smoke more than 100 cigarettes become regular smokers and one-third of those adolescents who experiment with tobacco go on to become nicotine dependent [Anthony et al., 1994; CDC, 2005; Mayhew et al., 2000]. Symptoms of dependence in these youths may appear within weeks of occasional tobacco use [DiFranza, 2008; DiFranza et al., 2000, 2002; Doubeni et al., 2010; Escobedo et al., 1993; O’Loughlin et al., 2002a, 2002b], particularly loss of control over their smoking [DiFranza et al., 2007; Scragg et al., 2008; Soteriades et al., 2011]. Early initiation of tobacco use is also associated with an increased number of daily cigarettes smoked in adulthood [Chen and Millar, 1998; D’Avanzo et al., 1994; Eisner et al., 2000; Everett et al., 1999; Fernandez et al., 1999] and a decreased rate of smoking cessation [Breslau and Peterson, 1996; Chen and Millar, 1998; Eisner et al., 2000; Lando et al., 1999]. Age of smoking onset in women is a significant predictor of cessation during pregnancy; a woman who initiates earlier is more likely
