Abstract
BACKGROUND: Limited research among adolescents and young adults (AYA) has assessed tobacco and marijuana co-use in light of specific products. We examined the patterns of past 30-day co-use of tobacco and marijuana products, and the product-specific associations among past 30-day use of these substances. METHODS: Data from three school-based convenience samples of California AYA (aged 15-22) (Sample 1 = 3008; Sample 2 = 1419; Sample 3 = 466) were collected during 2016-2017. Proportions of past 30-day co-use of tobacco (e-cigarettes, cigarettes, hookah, cigars) and marijuana (combustible, vaporized, edible, blunt) were estimated. Multivariable logistic regression analyses examined associations between use of each tobacco and marijuana product for individual samples, then the pooled analysis calculated combined ORs. RESULTS: In the three samples, 7.3-11.3% of participants reported past 30-day co-use. Combinations of e-cigarettes or cigarettes and combustible marijuana were the most common co-use patterns. Past 30-day use of e-cigarettes or cigarettes (vs. non-use) increased the odds of past 30-day use of all marijuana products [e-cigarettes: ORs (95%CI) ranging from 2.5 (1.7, 3.2) for edible marijuana to 4.0 (2.8, 5.2) for combustible marijuana; cigarettes: from 3.2 (2.1, 4.2) for vaporized marijuana to 5.5 (3.8, 7.3) for combustible marijuana]. Past 30-day use of hookah or cigars was positively associated with past 30-day use of three of four marijuana products, except for hookah and vaporized marijuana, and for cigars and combustible marijuana. CONCLUSIONS: Given various co-use patterns and significant associations among tobacco and marijuana products, interventions targeting AYA should address co-use across the full spectrum of specific products for both substances.