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Effects of dual use of e-cigarette and cannabis during adolescence on cigarette use in young adulthood
  1. Talat Islam1,
  2. Sandrah Eckel1,
  3. Feifei Liu1,
  4. Jessica Barrington-Trimis1,
  5. Alyssa F Harlow1,
  6. Neal Benowitz2,
  7. Adam Leventhal1,
  8. Rob McConnell1,
  9. Junhan Cho1
  1. 1Department of Population and Public Helath Sciences, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
  2. 2University of California San Francisco, San Francisco, California, USA
  1. Correspondence to Talat Islam, Department of Population and Public Helath Sciences, Keck School of Medicine, University of Southern California, Los Angeles, California, USA; islam{at}


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.

  • Addiction
  • Electronic nicotine delivery devices
  • Nicotine
  • Co-substance use
  • Public policy

Data availability statement

Data are available upon reasonable request.

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Data availability statement

Data are available upon reasonable request.

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  • Contributors TI was engaged in the planning, conducting, drafting, and reporting the study and is the guarantor for findings reported in the manuscript. JB-T was engaged in the acquisition and interpretation of the data. AH participated in interpretation and revision of the findings. SE was engaged in data analysis and drafting of the report. FL participated in data analysis. NB was engaged in the interpretation and revision of the study. AL participated in the interpretation and revision of the manuscript. RM was engaged in data acquisition and interpretation of the findings. JC was engaged in analysis, revision, interpretation and final approval of the study.

  • Funding The study was supported by the National Institutes of Health (grants U54CA180905, R21HD084812, P30ES007048 and 5P30CA014089).

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.