Who mixes tobacco with cannabis and does mixing relate to nicotine dependence?

Background: Cannabis users who mix tobacco with cannabis are exposed to nicotine in the tobacco. We identified characteristics of young adult cannabis users who mix and investigated whether mixing frequency is associated with nicotine dependence (ND). Methods: Data were collected in self-report questionnaires in 2017-20 from 788 young adults (44% male; mean (SD) age 30.6 (1.0) years) participating in a longitudinal investigation of the natural course of ND. Using multivariable logistic regression, we assessed whether any of 16 sociodemographic, lifestyle, psychosocial or other characteristics were associated with mixing among 313 past-year cannabis users. We also assessed whether mixing frequency was associated with ND among 289 past-year cannabis users who had ever smoked cigarettes controlling for age, sex, and other sources of nicotine (i.e., number of cigarettes smoked, other tobacco products, second-hand smoke exposure). Results: Of 788 participants, 40 % (n = 313) reported past-year cannabis use. Of these, 150 (48 %) reported mixing. Younger age, lower education and income, past-year cigarette use, use of other tobacco products and illicit drugs, poor coping skills and gambling were associated with mixing. Number of ICD-10 ND criteria endorsed was associated with mixing < weekly (b(95 % CI) = 0.3(0.02,0.7)) and weekly/daily (0.5(0.1,0.9)) after controlling for other sources of nicotine. Conclusion: Mixing is associated with ND and therefore may threaten tobacco control efforts by rendering quitting cigarette smoking more difficult among smokers who mix tobacco with cannabis. Mixing tobacco with cannabis should be considered as an additional source of nicotine exposure in studies of ND in young people.