Electronic cigarettes (e-cigarettes) are suggested as a harm reduction product for adults who smoke, but pose an addiction and health risk for non-smoking youth. Health warnings are a central regulatory strategy for reducing e-cigarette-related harms, yet their impact is less understood, and they may function differently across youth and adult populations. A rapid scoping review, searching Medline for any studies examining responses to e-cigarette health warnings presented on packaging or as stand-alone messages. Outcomes included perceived effectiveness and/or behavioral intentions. Double screening was conducted for titles, abstracts and full texts. Studies were grouped by youth-focused and adult-focused samples. E-cigarette warnings were coded for theme, target audience and use of vague language (e.g., “may”). In the final sample (n = 29, n = 201 unique warnings), nine youth-focused studies and 20 adult-focused studies met inclusion criteria. Among youth, warnings emphasizing concrete health harms, particularly brain development, lung damage, and chemical exposure risks, consistently produced stronger perceived harm, fear responses, and reduced interest in e-cigarette use compared with nicotine addiction warnings alone, but addiction-only messages were often perceived as familiar and insufficiently compelling. Youth interpreted vague language as weakening risk and reducing credibility. Harm reduction messages lowered perceived harm and, in some cases, increased openness to use, indicating poor suitability for youth audiences. Among adults, nicotine addiction warnings were consistently rated as clear and credible but were less effective than hazard-based warnings at discouraging use or motivating quitting. Harm reduction messages showed mixed effects: they sometimes increased willingness to try or switch to e-cigarettes among current smokers but increased ambiguity and reduced warning effectiveness among non-smokers. Responses varied substantially by user status and prior tobacco experience. No single warning approach advanced both youth prevention and adult harm reduction goals. Audience-segmented warning strategies were therefore essential to e-cigarette regulation seeking to protect youth while supporting harm reduction.
Klein et al. (Fri,) studied this question.