Research was supported by National Institute on Drug Abuse grant DA019377, complied with National Institutes of Health Y-27632 DOCA guidelines for the use of experimental animals and approved by Virginia Commonwealth University��s Institutional Animal Care and Use Committee. Declaration of Interests None declared.
Young adults have the highest smoking rates of any age group in the United States (Rock et al., 2007; Substance Abuse and Mental Health Services Administration, 2010); however, recent research indicates that young adult smoking may not mirror the typical daily habitual smoking of earlier generations. Light or intermittent smoking is common among young adults (Lenk, Chen, Bernat, Forster, & Rode, 2009; Wetter et al.

, 2004; White, Bray, Fleming, & Catalano, 2009) and typifies a pattern of smoking in social situations (Moran, Wechsler, & Rigotti, 2004; Waters, Harris, Hall, Nazir, & Waigandt, 2006). Among current smokers, intermittent smoking is more common among minorities (relative to Whites), young adults aged 18�C24 (relative to 45�C64 year olds), and individuals with a college education (relative to those with less education; Trinidad et al., 2009; Wortley, Husten, Trosclair, Chrismon, & Pederson, 2003). Among young adults, intermittent smokers smoke fewer cigarettes per day than daily smokers (Hassmiller, Warner, Mendez, Levy, & Romano, 2003; Lenk et al., 2009; Levy, Biener, & Rigotti, 2009), are less likely to feel addicted (Lenk et al., 2009), and less likely to consider themselves ��smokers�� (Lenk et al., 2009; Waters et al., 2006).

In one study of 990 young adults, 17%�C21% were intermittent smokers, and although college-attending individuals were less likely to smoke heavily than their noncollege-attending counterparts, they were equally likely to be light or intermittent smokers (White et al., 2009). A number of longitudinal studies spanning adolescence and early adulthood have identified two or more distinct smoking trajectories, yet most of these studies have relied on smoking measures that are not sensitive to the difference between intermittent and daily smoking (Chassin, Presson, Pitts, & Sherman, 2000; Juon, Ensminger, & Sydnor, 2002; White, Johnson, & Buyske, 2000; White, Nagin, Replogle, & Stouthamer-Loeber, 2004; White, Pandina, & Chen, 2002).

Three studies have investigated intermittent smoking patterns longitudinally among young adults, yet it remains unclear whether intermittent smoking is truly a distinct stable pattern of use. First, Colder et al. (2006) documented an overall decrease in smoking over the course of the first year of college but did not distinguish between groups with different Drug_discovery smoking patterns. Second, in their study of 548 college students, Wetter et al. (2004) found that 87% of daily smokers and 50% of occasional smokers continued to smoke 4 years later, and occasional smokers were more likely to quit than to maintain their occasional pattern of use or transition to daily use.