Since the early 1970’s, a growing body of evidence has suggested a link between the neuropsychological effects of cannabis and ethanol consumption. Specifically, studies of the affective, cognitive, and psychomotor effects of these two substances in humans found evidence of a potential cross-tolerance to ethanol amongst cannabis users (Jones and Stone, 1970; MacAvoy and Marks, 1975). More recently, epidemiological studies of US populations indicate that for individuals with a CUD there is 45 – 81% lifetime prevalence of developing a comorbid AUD (Agosti et al., 2002; Regier et al., 1990; Stinson et al., 2006). In a clinical study of adolescents with an AUD, over 70% reported use of cannabis within the past year, and the mean frequency of cannabis use for this group was between 16 and 20 days per month (Martin et al., 1996). In addition, data from a national computerized telephone survey show that individuals who responded as using marijuana and ethanol simultaneously engaged in significantly more binge drinking and were more likely to have alcohol dependence (Midanik et al., 2007). Together, these findings demonstrate a high prevalence of comorbidity between AUDs and CUDs.
