Marijuana is the most frequently used illicit substance, and marijuana abuse and dependence are highly prevalent in the United States (American Psychiatric Association, 2000; Compton et al., 2007; Johnston et al., 2009; Johnston et al., 2010; Office of Applied Studies, 2008). Chronic, regular use is associated with DSM-IV diagnoses of marijuana use disorders (Grant and Pickering, 1998). Such disorders are associated with marijuana withdrawal, unemployment, personality dysfunction, crime, respiratory problems and other psychiatric disorders (Budney et al., 2004; Budney and Moore, 2002; Hall and Lynskey, 2009; Haney, 2005; Hasin et al., 2008; Pedersen and Skardhamar; Taylor et al., 2000).
