Objective We sought to systematically review the literature on electronic nicotine delivery systems (ENDS, also called electronic cigarettes) awareness, use, reactions and beliefs. Data sources We searched five databases for articles published between 2006 and 1 July 2013 that contained variations of the phrases ‘electronic cigarette’, ‘e-cigarette’ and ‘electronic nicotine delivery’. Study selection Of the 244 abstracts identified, we excluded articles not published in English, articles unrelated to ENDS, dissertation abstracts and articles without original data on prespecified outcomes. Data extraction Two reviewers coded each article for ENDS awareness, use, reactions and beliefs. Data synthesis 49 studies met inclusion criteria. ENDS awareness increased from 16% to 58% from 2009 to 2011, and use increased from 1% to 6%. The majority of users were current or former smokers. Many users found ENDS satisfying, and some engaged in dual use of ENDS and other tobacco. No longitudinal studies examined whether ENDS serve as ‘gateways’ to future tobacco use. Common reasons for using ENDS were quitting smoking and using a product that is healthier than cigarettes. Self-reported survey data and prospective trials suggest that ENDS might help cigarette smokers quit, but no randomised controlled trials with probability samples compared ENDS with other cessation tools. Some individuals used ENDS to avoid smoking restrictions. Conclusions ENDS use is expanding rapidly despite experts’ concerns about safety, dual use and possible ‘gateway’ effects. More research is needed on effective public health messages, perceived health risks, validity of self-reports of smoking cessation and the use of different kinds of ENDS.

Background More US adolescents use e-cigarettes than smoke cigarettes. Research suggests flavoured e-cigarettes appeal to youth, but little is known about perceptions of and reasons for attraction to specific flavours. Methods A national sample of adolescents (n=1125) ages 13–17 participated in a phone survey from November 2014 to June 2015. We randomly assigned adolescents to respond to survey items about 1 of 5 e-cigarette flavours (tobacco, alcohol, menthol, candy or fruit) and used regression analysis to examine the impact of flavour on interest in trying e-cigarettes and harm beliefs. Results Adolescents were more likely to report interest in trying an e-cigarette offered by a friend if it were flavoured like menthol (OR=4.00, 95% CI 1.46 to 10.97), candy (OR=4.53, 95% CI 1.67 to 12.31) or fruit (OR=6.49, 95% CI 2.48 to 17.01) compared with tobacco. Adolescents believed that fruit-flavoured e-cigarettes were less harmful to health than tobacco-flavoured e-cigarettes (p<0.05). Perceived harm mediated the relationship between some flavours and interest in trying e-cigarettes. A minority of adolescents believed that e-cigarettes did not have nicotine (14.6%) or did not know whether they had nicotine (3.6%); these beliefs did not vary by flavour. Discussion Candy-flavoured, fruit-flavoured and menthol-flavoured e-cigarettes appeal to adolescents more than tobacco-flavoured or alcohol-flavoured e-cigarettes. This appeal is only partially explained by beliefs about reduced harm. Given adolescents' interest in trying e-cigarettes with certain flavours, policymakers should consider restricting advertisements promoting flavoured products in media that reach large numbers of young people. Future research should examine other reasons for the appeal of individual flavours, such as novelty and perceived luxury.

Purpose: More adolescents “vape” (use e-cigarettes and similar devices) than smoke, but little is known about how underage users obtain vaping devices. This knowledge could inform efforts to prevent youth access. Design: Original cross-sectional survey with social media recruitment. Settings: Online. Participants: A total of 1729 adolescents (2809 qualified on screener; completion rate 61.6%) aged 15 to 17 years who vaped in the past 30 days. Measures: Adolescents’ vaping attitudes, ownership of vaping devices, how they obtain devices, and frequency of borrowing others’ devices. Analysis: Logistic regression. Results: Most adolescents (78.2%) owned a vaping device. The most common sources were purchasing from a store or online (31.1%), buying from another person (16.3%), or giving someone money to purchase for them (15.0%). The majority (72.8%) had used someone else’s vaping device in the past 30 days. Adolescents who vaped more often, did not own a vaping device, vaped in social situations, and had previously been refused purchase were more likely to frequently borrow others’ devices. Conclusions: Despite high rates of ownership, many adolescents borrowed devices, suggesting that borrowing is part of users’ social experience, not just a means of acquisition. Although better enforcement of age restrictions could lessen purchasing, future research is needed to understand why adolescents borrow and how their acquisition sources shift over time. That information could be harnessed for targeted, borrowing-related antivaping campaigns.