Varenicline for Co-occurring Cannabis and Tobacco Use

Inclusion Criteria: * Able to speak English * Uses cannabis at least 5 days in the past 7 days * Current or former tobacco smoker * Has not taken varenicline in the past 30 days * Not pregnant, trying to conceive or breastfeeding * Able to provide informed consent * Test positive for cannabinoids by urine toxicology Exclusion Criteria: * Unstable medical or psychiatric illness * Opioid use disorder was initially exclusionary but eligibility criteria were revised after 32 individuals were screened to facilitate recruitment.