This explanation is consistent with reports that dual tobacco users differ from users of a single tobacco product (Wetter et al., 2002), escalate more quickly to heavy tobacco use and nicotine dependence (Rosendahl, Galanti, & Gilljam, 2008), selleckchem Vandetanib smoke more cigarettes than exclusive smokers, and had a doubling of lung cancer mortality rate in epidemiological studies compared with exclusive smokers (Accortt, Waterbor, Beall, & Howard, 2002; Accortt, Waterbor, Beall, Howard, & Brooks, 2005). In this study, school was the unit of randomization since students from the same school were likely to be more correlated than those from different schools. Analyses for intervention effects used GEE models to account for the school clusters.
In addition, we considered that one possible explanation for our findings might be seasonal effects, that is, ST use during sport seasons and warmer weather but smoking during off seasons and colder weather, however, no such seasonal effect was evident. Moreover, although several baseline correlates of ST use were associated with loss to follow-up, there was no difference between the intervention and no-intervention groups in this regard. Baseline ST users, however, were more likely to be lost to follow-up than nonusers. This study also found that a greater percentage of baseline ��nonsmoking ST users�� smoked at 1-year follow-up than baseline ��non-ST-using smokers�� who used ST at follow-up.
These findings are consistent with those of Forrester, Biglan, Severson, and Smolkowski (2007) who reported that use of ST in a population of adolescent boys in 7th and 9th grades was a significant risk factor for subsequent smoking 2 years later even when controlling for other factors, such as parent, sibling, or close friend smoking; low academic grades; 30-day alcohol use; and a scale measure of deviant behavior. Moreover, in that study, smoking did not predict ST use between 9th and 11th graders 2 years later, suggesting that the relationship between ST use and smoking went only in one direction (Severson, Forrester, & Biglan, 2007). Currently, there is debate in the literature among those who report that ST use is a risk factor for cigarette smoking (Forrester et al., 2007; Haddock et al., 2001; Severson et al., 2007; Tomar, 2003a, 2003b; Tomar & Loree, 2004) and those who report no such relationship (Kozlowski, O��Connor, Edwards, & Flaherty, 2003; O��Connor, Flaherty, Edwards, & Kozlowski, 2003; O��Connor, Kozlowski, Flaherty, & Edwards.
2005). Although the suggestion that ST use precedes cigarette smoking has been in the literature for some time (Hatsukami & Severson, 1999; Severson et al., 1991), recent policy discussions on whether ST can serve as a safer alternative to cigarette smoking and whether ST manufacturers could adjust Dacomitinib their warning labels have highlighted this issue.