BackgroundStudies demonstrated that adolescent e-cigarette use is associated with subsequent tobacco smoking, commonly referred to as the gateway effect. However, most studies only investigated gateways from e-cigarettes to tobacco smoking. This study replicates a cornerstone study revealing a positive association between both adolescent e-cigarette use and subsequent tobacco use; and tobacco and subsequent e-cigarette use in the Netherlands and Flanders.DesignThe longitudinal design included baseline (n=2839) and 6-month (n=1276) and 12-month (n=1025) follow-up surveys among a school-based cohort (mean age: 13.62). Ten high schools were recruited as a convenience sample. The analyses involved (1) associations of baseline e-cigarette use and subsequent tobacco smoking among never smokers; (2) associations of e-cigarette use frequency at baseline and tobacco smoking frequency at follow-up; and (3) the association of baseline tobacco smoking and subsequent e-cigarette use among non-users of e-cigarettes.FindingsConsistent with prior findings, baseline e-cigarette use was associated with higher odds of tobacco smoking at 6-month (OR=1.89; 95% CI 1.05 to 3.37) and 12-month (OR=5.63; 95% CI 3.04 to 10.42) follow-ups. More frequent use of e-cigarettes at baseline was associated with more frequent smoking at follow-ups. Baseline tobacco smoking was associated with subsequent e-cigarette use (OR=3.10; 95% CI 1.58 to 6.06 at both follow-ups).ConclusionOur study replicated the positive relation between e-cigarette use and tobacco smoking in both directions for adolescents. This may mean that the gateway works in two directions, that e-cigarette and tobacco use share common risk factors, or that both mechanisms apply.

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While there has been a growth in recent years in recovery research, much of this has been from the US and there is very little comparative research in this area. This paper describes the rationale, conceptual foundations and methods for a prospective, multi-country, cohort study aimed to map pathways to recovery from problematic illicit drug use, with a specific focus on gender differences in recovery pathways. Our study combines qualitative and quantitative components and examines the impact of recovery policy on the accessibility and viability of recovery pathways in England, Scotland, Belgium, and the Netherlands. Additionally, the paper describes five processes through which mechanisms for behaviour change for recovery may be triggered. This study will provide opportunities for linking recovery outcome research with analyses of national recovery policies, while also addressing the gap in literature around female pathways to recovery.