Research has demonstrated associations between e-cigarette use and tobacco use among youth. However, few studies have examined whether reciprocal relationships exist between e-cigarette and tobacco use. The objective of this study was to examine whether bi-directional associations exist between e-cigarette and tobacco use in a large longitudinal sample of Canadian youth. A longitudinal sample of secondary students (n = 6729) attending 87 schools in Ontario and Alberta, Canada, who completed the COMPASS student questionnaire across three waves (from 2014-2015 to 2016-2017) was identified. Using cross-lagged models, we explored bi-directional associations between current tobacco and e-cigarette use, adjusting for relevant covariates. Our findings showed that current e-cigarette use predicted subsequent tobacco use between Wave 1 (W1) and Wave 2 (W2) of the study (W1-2: OR = 1.54, 95% CI = 1.37-1.74). Similarly, current tobacco use predicted e-cigarette use during earlier waves of the study (W1-2: OR = 1.43, 95% CI = 1.30-1.58). However, these relationships dissipated in later waves, when tobacco use no longer predicted e-cigarette use (W2-3: OR = 1.07, 95 % CI = 0.99-1.16). This study extends prior work that focused mainly on the association between e-cigarette and subsequent tobacco use. Specifically, our findings portray a more complex relationship, where e-cigarette use may influence and be influenced by tobacco use.
Keywords: bi-directional; e-cigarette; electronic cigarettes; tobacco; youth.