LAUSR

BACKGROUND Some studies suggest cannabis use negatively affects tobacco cessation outcomes, but findings have been mixed. We examined whether cannabis use was associated with tobacco cessation outcomes in a real-world primary care setting. METHODS The analytic dataset consisted of 35,246 patients who enrolled between 2014 and 2016 in a primary care-based smoking cessation program in Ontario, Canada. Past 30-day cannabis use, for recreational or medical purposes, was self-reported at enrollment. Thirty-day point prevalence tobacco smoking abstinence was self-reported via online or telephone survey at 6 months post-enrollment. RESULTS Thirty days prior to enrollment, 79.9 % of patients had not used cannabis, 16.3 % used cannabis for recreational purposes only, and 3.8 % used cannabis for medical purposes. Unadjusted and adjusted odds of tobacco cessation at 6 months were reduced for patients using cannabis compared to non-users (ORs = 0.76-0.86, ps<0.05). When cannabis use was categorized by purpose, both unadjusted and adjusted odds of cessation were significantly lower for recreational users (ORs = 0.77-0.84, ps<0.05). Medical users had decreased odds of cessation in unadjusted analysis (OR = 0.74, 95 % CI = 0.61-0.89, p = 0.001), but not after adjustment for potential confounders. However, post-estimation contrasts did not indicate a significant difference between the effect of recreational and medical cannabis use. CONCLUSIONS In a large real-world sample of patients seeking smoking cessation treatment, concurrent cannabis use was associated with decreased success with quitting smoking. Recreational cannabis use was consistently related to poorer cessation outcomes, but medical use was not. Additional research is needed to inform treatment strategies for this growing sub-population of smokers.