Sweet flavors and the addictive potential of e-cigarettes: A systematic narrative review.

Introduction: Population-based surveys indicate that sweet and fruity flavors in the e-liquids are key drivers of attractiveness of e-cigarettes (ECIGs). However, their role in the addictive potential of ECIGs is less well established. This systematic review aimed to synthetize the available evidence on the impact of sweet and fruity flavors on indicators of nicotine dependence. Methods: A systematic review was conducted in PubMed, Embase and Google Scholar in accordance with PRISMA guidelines. Studies were eligible if they reported the effects of sweet/fruity flavors in ECIGs on (1) consumption rate, (2) vaping topography and nicotine intake, (3) reward and reinforcement, and (4) indicators of nicotine dependence. Studies limited to qualitative assessments of flavor properties were excluded. Initially, 454 studies were identified and screened independently by two reviewers, resulting in 23 eligible studies. Risk of bias and study quality were evaluated using the Johanna Briggs Institute Critical Appraisal Tools. Results: Sweet/fruity flavors were consistently associated with increased consumption rates and a higher puff number and volume, leading to greater nicotine exposure. Several studies also demonstrated that sweet flavors enhanced the reward and reinforcement of ECIG use. However, findings regarding their effects on craving and withdrawal were inconsistent. Conclusions: Sweet/fruity flavors appear to increase the abuse liability of ECIGs, but the evidence remains inconclusive. Additional high-quality studies that adequately control for known covariates are required to clarify their contribution and the independent role of flavors in nicotine dependence. Implications: These findings, together with emerging toxicological data on ECIGs, should be carefully considered in regulatory decisions regarding flavor bans in ECIGs.