Effects of dual use of e-cigarette and cannabis during adolescence on cigarette use in young adulthood.

Introduction E-cigarette
and cannabis use by
adolescents are risk factors for smoking initiation. We
hypothesised that increasingly common dual use of
e-cigarette
and cannabis in adolescence leads to more
frequent cigarette smoking in young adulthood.
Methods Data are from a prospective cohort study
in Southern California, where 1164 participants who
ever used nicotine products in their lifetime completed
surveys in 12th grade (T1:2016), and at 24-month
(T2)
and 42-month
(T3) follow-ups.
Past 30-day
use (number
of days: range=0–30) of cigarettes, e-cigarettes
and
cannabis, and nicotine dependence, were assessed in
each survey. Nicotine dependence for cigarettes and
e-cigarettes
was assessed using original and modified
(for e-cigarette)
Hooked on Nicotine Checklists (number
of dependent products: range=0–2). Path analysis
examined the mediation process via nicotine dependence
linking baseline e-cigarette
and cannabis use to
subsequent increased cigarette use.
Results Baseline exclusive use of e-cigarettes
(baseline
prevalence, 2.5%) was associated with 2.61-fold
increase in frequency of smoking days at T3 (95% CI
1.04 to 13.1), exclusive cannabis use (26.0%) with
2.58-fold
increase (95% CI 1.43 to 4.98), and dual use
(7.4%) with 5.84-fold
increase (95% CI 3.16 to 12.81),
compared with baseline non-users.
Nicotine dependence
at T2 mediated 10.5% (95% CI 6.3 to 14.7) and 23.2%
(95% CI 9.6 to 36.3) of the association of cannabis and
dual use, respectively, with increased smoking at T3.
Discussion Adolescent e-cigarette
and cannabis use
was associated with more frequent smoking during
young adulthood, with larger effects of dual use.
Associations were partially mediated through nicotine
dependence. Dual use of cannabis and e-cigarettes
may
contribute to the development of nicotine dependence
and increased use of combustible cigarettes.

Islam T, Eckel S, Liu F, et al. Effects of dual use of e-cigarette and cannabis during adolescence on cigarette use in young adulthood. Tobacco control. Published online May 5, 2023. doi:10.1136/tc-2022-057542