Consistent with previous studies (Anthony et al., 1994; Behrendt et al., 2009; Breslau et al., 2001; Chen et al., 2005; O'Brien and Anthony, 2005; Ridenour et al., 2003; Ridenour et al., 2005; Wagner and Anthony, 2002a, 2007), the lag period from substance use onset to dependence was greater for nicotine and alcohol than for cannabis or cocaine. Differences in the speed of transition from use to dependence may be related to addictive liability and pharmacokinetic properties of the substances (Koob and Volkow, 2009; Lupica et al., 2004; Nestler, 2005; Ridenour et al., 2005), as well as their availability, legality and social acceptability (Ridenour et al., 2005). Confirming prior findings (Agrawal et al., 2008; Drgon et al., 2006; Kandel, 2002; Stinson et al., 2005), use of and dependence on other substance increased the risk of transition to dependence. In our sample, one third of alcohol users and half of nicotine users had an additional SUD, compared to more than 80% of cannabis users and 90% of cocaine users. The accelerated speed of transition from cannabis or cocaine use to dependence given
