Which type of tobacco product warning imagery is more effective and sustainable over time? A longitudinal assessment of smokers in Canada, Australia and Mexico

Objective This study examined smokers' responses to pictorial health warnings (PHWs) with different types of imagery under natural exposure conditions. Methods Adult smokers from online panels in Canada (n=2357), Australia (n=1671) and Mexico (n=2537) were surveyed every 4 months from 2012 to 2013. Participants were shown PHWs on packs in their respective countries and asked about: (1) noticing PHWs; (2) negative affects towards PHWs; (3) believability of PHWs; (4) PHW-stimulated discussions; and (5) quit motivation due to PHWs. Country-specific generalised estimating equation models regressed these outcomes on time (ie, survey wave), PHW imagery type (ie, symbolic representations of risk, suffering from smoking and graphic depictions of bodily harm) and interactions between them. Results In all countries, PHW responses did not significantly change over time, except for increased noticing PHWs in Canada and Mexico, increased negative affect in Australia and decreased negative affect in Mexico. For all outcomes, symbolic PHWs were rated lower than suffering and graphic PHWs in Canada (the only country with symbolic PHWs). Graphic PHWs were rated higher than suffering PHWs for negative affect (all countries), discussions (Canada) and quit motivation (Australia). Suffering PHWs were rated higher than graphic PHWs for noticing PHWs (Canada), believability (all countries), discussions (Australia and Mexico) and quit motivation (Mexico). Changes in noticing, believability and discussions varied somewhat by imagery type across countries. Conclusions The different PHW imagery appears to have different pathways of influence on adult smokers. Reactions to specific PHWs are similar over 1-2 years, suggesting that wear-out of PHW effects is due to decreased attention rather than the diminishing effectiveness of content.