Perceived effectiveness of pictorial health warnings among Mexican youth and adults: a population-level intervention with potential to reduce tobacco-related inequities

Pictorial health warnings on cigarette packages are a prominent and effective means of communicating the risks of smoking; however, there is little research on effective types of message content and socio-demographic effects. This study tested message themes and content of pictorial warnings in Mexico. Face-to-face surveys were conducted with 544 adult smokers and 528 youth in Mexico City. Participants were randomized to view 5-7 warnings for two of 15 different health effects. Warnings for each health effect included a text-only warning and pictorial warnings with various themes: "graphic" health effects, "lived experience", symbolic images, and testimonials. Pictorial health warnings were rated as more effective than text-only warnings. Pictorial warnings featuring "graphic" depictions of disease were significantly more effective than symbolic images or experiences of human suffering. Adding testimonial information to warnings increased perceived effectiveness. Adults who were female, older, had lower education, and intended to quit smoking rated warnings as more effective, although the magnitude of these differences was modest. Few interactions were observed between socio-demographics and message theme. Graphic depictions of disease were perceived by youth and adults as the most effective warning theme. Perceptions of warnings were generally similar across socio-demographic groups.