Cannabis use and use disorders are prevalent in the industrialized world, including in Europe, the United States, Canada, and Australia (Anthony et al. 1994; Swift et al. 2001; Vega et al. 2002; SAMHSA 2003). In the U.S., cannabis use disorders (abuse and dependence) rank third, behind only tobacco and alcohol, in frequency of substance use disorders (Anthony et al. 1994; SAMHSA 2003). The 2003 National Survey on Drug Use and Health (SAMHSA 2003) reported that 40.6% of the U.S. population had used cannabis or hashish during their lifetime and that 4.2 million individuals age 12 years and older met criteria for past year cannabis abuse or dependence using DSM-IV (American Psychiatric Association 1994) criteria. The 2001–2002 National Epidemiologic Survey on Alcohol and Related Conditions (NESARC) found that 8.45% of the population had a lifetime DSM-IV diagnosis of either cannabis dependence (1.30%) or abuse (7.16%) (Conway et al. 2006). Using DSM-III-R criteria, the National Co morbidity Survey (NCS) found that 46.3% of the population had a lifetime history of extra medical use of cannabis and 4.2 % of the population aged 18–54 years had a lifetime DSM-III-R (American Psychiatric Association 1987) history of cannabis dependence (Anthony et al. 1994).
