Discordance between perceived and actual tobacco product use prevalence among US youth: a comparative analysis of electronic and regular cigarettes.

Importance Two components of social norms-descriptive (estimated prevalence) and injunctive (perceived acceptability)-can influence youth tobacco use. Objective To investigate electronic cigarettes (e-cigarette) and cigarette descriptive norms and measure the associations between overestimation of e-cigarette and cigarette prevalence and tobacco-related attitudes and behaviours. Design Cross-sectional. Setting School-based, using paper-and-pencil questionnaires. Participants US 6th-12th graders participating in the 2015 (n=17 711) and 2016 (n=20 675) National Youth Tobacco Survey. Exposure Students estimated the percent of their grade-mates who they thought used e-cigarettes and cigarettes; the discordance between perceived versus grade-specific actual prevalence was used to categorise students as overestimating (1) neither product, (2) e-cigarettes only, (3) cigarettes only or (4) both products. Outcomes Product-specific outcomes were curiosity and susceptibility (never users), as well as ever and current use (all students). Descriptive and multivariable logistic regression analyses were performed. Statistical significance was at P<0.05. Data were weighted to be nationally representative. Results More students overestimated cigarette (74.0%) than e-cigarette prevalence (61.0%; P<0.05). However, the associations between e-cigarette-only overestimation and e-cigarette curiosity (adjusted OR (AOR)=3.29), susceptibility (AOR=2.59), ever use (AOR=5.86) and current use (AOR=8.15) were each significantly larger than the corresponding associations between cigarette-only overestimation and cigarette curiosity (AOR=1.50), susceptibility (AOR=1.54), ever use (AOR=2.04) and current use (AOR=2.52). Despite significant declines in actual e-cigarette use prevalence within each high school grade level during 2015-2016, perceived prevalence increased (11th and 12th grades) or remained unchanged (9th and 10th grades). Conclusions Four of five US students overestimated peer e-cigarette or cigarette use. Counter-tobacco mass media messages can help denormalise tobacco use.