BACKGROUND AND AIMS E-cigarette flavours have the potential to impact the appeal, harms and use of e-cigarettes and combustible tobacco. Systematic reviews have synthesised evidence on their impacts but have always focused on specific outcomes or populations. This overview aimed to draw together syntheses from past systematic reviews of e-cigarette flavours to provide a holistic, population-wide view.

METHODS Overview of systematic reviews investigating the impacts of e-cigarette flavours on any outcome. We searched six databases to February 2024, and appraised reviews using AMSTAR2. We used association direction plots and narratively synthesised results.

RESULTS We included 32 reviews (11 higher quality; 21 lower). Reviews reported impacts of e-cigarette flavours on: appeal/perceptions of vaping (13 reviews); harms (12); smoking (7); and vaping (13) behaviours. Availability of non-tobacco e-cigarette flavours may increase the appeal of (8 reviews) and motivation to try/continue using e-cigarettes (5) and decrease harm perceptions (5). There were no clear differences in impacts based on age or history of combustible tobacco use, and little difference in findings between higher and lower quality reviews. Two reviews indicated that among adolescents, experimenting with different flavours increased e-cigarette appeal. Twelve reviews indicated that a range of specific flavours (including cinnamon, menthol and various sweet/fruity flavours) may be harmful; this often came from in vitro experiments and chemical analyses. Findings were inconclusive on the impact of e-cigarette flavours on smoking cessation (six reviews not showing clear impact), smoking initiation (two reviews not showing clear impact) and vaping initiation (two reviews showing increased initiation and two not showing clear impact).

CONCLUSIONS Non-tobacco flavourings for e-cigarettes may increase e-cigarette appeal and harms; this increase may vary by flavour and apply across different population groups. The impacts of e-cigarette flavours on e-cigarette and cigarette use are inconclusive.