Grant: CIHR Fellowship

Canada has one of the highest rates of marijuana use in the world and it is estimated that 25% of individuals seeking treatment for substance dependence are those with problematic marijuana use. Unfortunately, the demand for marijuana treatment has far outpaced the development of effective treatment strategies and the lack of currently available medications for marijuana dependence needs to be addressed. This is especially critical for the Canadian population given that legalization of marijuana for recreational purposes continues to gain momentum combined with the observable and steady increase in the number of individuals consuming marijuana on a daily basis. Tobacco consumption occurs at high rates among marijuana users, and co-users who are attempting to quit marijuana are almost 10 times more likely to relapse than those who do not smoke tobacco cigarettes. Targeting both marijuana and tobacco use concurrently may maximize marijuana treatment outcomes in this high-risk population. Therefore this study will directly assess how tobacco use and novel medications (varenicline and nabilone) influence relapse to marijuana, with the aim of using these data to improve marijuana treatment outcomes. We predict that the combination of varenicline and nabilone, medications that target tobacco and marijuana use respectively, will most effectively improve marijuana relapse rates compared to varenicline alone or placebo. Participants will be assessed in both an outpatient and highly-controlled inpatient laboratory setting to determine the effects of tobacco, varenicline+nabilone, varenciline alone and placebo on marijuana outcomes (level of intoxication, marijuana consumption, withdrawal severity and time to relapse). It is the hope that findings from this study will help guide and establish a much-needed pharmacological treatment approach for individuals struggling with this prevalent and problematic substance use disorder.