Medical marijuana legalization and cigarette and marijuana co-use in adolescents and adults.

BACKGROUND: Medical marijuana legalization is associated with a higher prevalence of marijuana use which may affect cigarette use and nicotine dependence in co-users. In the present study, we examined relationships between statewide legalization of medical marijuana and prevalence of cigarette and marijuana co-use and nicotine dependence in co-using adolescents and adults. METHODS: Data were analyzed from the 2013 National Survey on Drug Use and Health. We compared cigarette and marijuana co-use in the past 30days across age categories (12-64 years) by statewide medical marijuana legalization. Logistic regression models were used to estimate the odds of having nicotine dependence among current cigarette smokers who also reported past 30-day marijuana use and "ever but not current" marijuana use (vs. "never" use) adjusting for covariates including statewide legalization of medical marijuana. RESULTS: Overall, 5.1% of the sample reported past 30-day cigarette and marijuana co-use and a higher proportion of co-users resided in states where medical marijuana was legal compared to illegal (5.8% vs. 4.8%; p=0.0011). Co-use was associated with greater odds of having nicotine dependence compared to cigarette-only use across age categories. Odds were highest and up to 3-times higher in adolescents aged 12-17 years (OR=3.54; 95%CI: 1.81-6.92) and adults aged 50-64 years (OR=3.08; CI: 1.45-6.55). CONCLUSION: Marijuana policy could inadvertently affect cigarette and marijuana co-use and pose challenges to tobacco cessation.