PROs might be considered for stratification purposes in future trials, as they were often better predictors of survival than PS. Studies are needed to determine whether interventions that improve PROs also increase survival and to identify explanatory mechanisms through which PROs relate to survival.

A vast majority of U.S. young adults use social media such as Facebook and Instagram daily. Research suggests that young adults are commonly exposed to e-cigarette-related marketing or user-generated content on the social media they use. Currently, however, there is limited empirical evidence as to how social media e-cigarette exposure is associated with e-cigarette use beliefs and behavior. In particular, limited evidence exists to support the proposition that social media e-cigarette exposure is uniquely associated with e-cigarette use, even after adjusting for the effects of e-cigarette use in young adults' in-person or 'offline' social networks. This study was conducted to test the hypotheses that 1) social media e-cigarette exposure is associated with e-cigarette use outcome expectancies and current e-cigarette use; and 2) the association between social media and e-cigarette use is linked via outcome expectancies. We collected cross-sectional data from a sample of 470 young adult college students in Hawaii. Hypotheses were tested by fitting a structural equation model to the data. The model accounted for the associations of demographic variables, cigarette smoking history, as well as e-cigarette use in individuals' actual social networks with expectancies and behavior. Results indicated that social media e-cigarette exposure was associated with current e-cigarette use indirectly through two of the four positive outcome expectancies examined, namely, positive "smoking" experience and positive sensory experience. We discuss the implications of the findings in the context of tobacco control efforts.

Objective To characterize smokers who are likely to use electronic- or "e-"cigarettes to quit smoking. Methods Cross-sectional data were obtained from 1567 adult daily smokers in Hawaii using paper-and-pencil survey. Analyses were conducted using logistic regression. Results Thirteen percent of the participants reported having ever-used e-cigarettes to quit smoking. Smokers who had used e-cigarettes to quit smoking reported higher motivation to quit, higher quitting self-efficacy, and longer recent quit duration compared to other smokers. Age (OR= 0.98, 95% CI [0.97, 0.99]) and Native Hawaiian ethnicity (compared to Whites) (OR= 0.68, 95% CI [0.45, 0.99]) were inversely associated with increased likelihood of e-cigarette ever-use for cessation. Other significant correlates of e-cigarette ever-use for cessation were: higher motivation to quit (OR= 1.14, 95% CI [1.08, 1.21]), quitting self-efficacy (OR= 1.18, 95% CI [1.06, 1.36]) and ever-use of U.S. Food and Drug Administration-approved cessation aids such as nicotine gum (OR= 3.72, 95% CI [2.67, 5.19]). Conclusions Smokers who try e-cigarettes to quit smoking seem serious about wanting to quit. Despite lack of evidence regarding efficacy, smokers seem to treat e-cigarettes as valid alternatives to FDA-approved cessation aids. Research is needed to test the safety and efficacy of e-cigarettes as cessation aids.

The revised youth e-cigarette outcome expectancies measure adds new items informed by recent qualitative research with young adult e-cigarette users, especially in the domain of positive "smoking" experience. Positive "smoking" experience represents beliefs that use of e-cigarettes provides outcomes associated with a better "smoking" alternative: for example, an alternative that is more socially approved, more suitable for indoor use, and that provides a safer means of enjoying nicotine. In addition, we tested a short, 8-item version of the measure which may be more easily incorporated into surveys. We tested the validity of the revised measure, both long and short versions, in terms of factor structure and associations of the expectancy factors with current e-cigarette use, e-cigarette use susceptibility, and e-cigarette use dependence. Participants were young adults (N=470; 65% women; mean age=20.9, SD=2.1). Results replicated the findings of the previous study as well as highlighted the importance of the added domain of positive "smoking" experience and the validity of the short scale. Furthermore, results showed that positive outcome expectancies are strongly associated with e-cigarette use dependence. The long and short versions of the revised youth e-cigarette outcome expectancies scale appear to be valid and useful for application not only among cigarette smokers and e-cigarette users but also among never smokers and never e-cigarette users.