Again confirming the results of previous studies, there was a high degree of association or comorbidity between the extent of cannabis involvement and measures of other substance use and abuse/dependence and psychiatric illness. Individuals who met criteria for cannabis abuse or dependence had rates of these disorders that were 1.8–56.5 times higher than the corresponding rates among individuals who reported never using cannabis (see Table 5) while individuals who had used cannabis but did meet criteria for abuse or dependence having rates of these outcomes that were intermediate between these two groups. Multiple explanations have been advanced to explain the associations between cannabis use and other drug use/psychiatric morbidity including that cannabis use -– and particularly heavy or symptomatic use — predisposes individuals both to use other substances and to develop substance use disorders and other psychiatric disorders. Thus, for example, it has been proposed that early onset cannabis use may increase risks for the development of MDD among women (Patton et al., 2002), Alternatively, it has been suggested that drug use may develop as a result of attempts to
