Impact of e-cigarette health warnings on motivation to vape and smoke.

BACKGROUND: A prevailing hypothesis is that health warnings for electronic cigarettes (e-cigarettes) could drive people away from vaping and towards smoking cigarettes. We consider an alternative hypothesis that e-cigarette warnings discourage both vaping and smoking. METHODS: Participants were a national convenience sample of 2218 US adults who used e-cigarettes, cigarettes or both. In August 2018, we randomised participants to one of three warning (control text about littering, text-only e-cigarette warning or pictorial e-cigarette warning). We further randomised participants viewing e-cigarette warnings to one of three (nicotine addiction, health hazards of use, or both health hazards and harms of use). The preregistered primary outcome was intentions to quit vaping among e-cigarette users. Secondary outcomes included interest in smoking and Tobacco Warnings Model constructs: attention, negative affect, anticipated social interactions and cognitive elaboration. RESULTS: Text warnings elicited higher intentions to quit vaping than control among e-cigarette users (=0.44, p<0.001), and pictorial warnings elicited still higher intentions to quit vaping than text (=0.12, p<0.05). Text warnings elicited lower interest in smoking compared with control among smokers (p