Graphic yellow health warnings on cannabis packaging were most effective at reducing product appeal and increasing risk perception

Pictorial (graphic) health warnings were generally more effective than text-only warnings across outcomes. Pictorial warnings with yellow backgrounds specifically decreased product appeal and interest in trying cannabis and increased harm perception compared to all other designs (text-only white, text-only yellow, pictorial white, no warning). The most effective warning themes were mental health, smoke toxicity, aesthetic implications, and traffic accidents.

Online experiment with 533 participants in Colombia using a between-subjects design. Participants were randomly assigned to 5 package conditions. Measured product appeal, perceived addictiveness, harm perception, and interest in trying cannabis products via attention task and ratings.

As cannabis legalization spreads, evidence-based warning label design can inform regulatory frameworks. This is among the first studies to experimentally test specific design elements of cannabis health warnings.

Lessons from tobacco warning labels suggest that design matters enormously for effectiveness. This study provides a cannabis-specific evidence base that regulators can use to maximize the public health impact of required packaging warnings.

Online experiment with Colombian participants; may not generalize to other cultural contexts. Measured intentions and perceptions, not actual behavior change. Single exposure; repeated exposure may produce habituation. Does not address warning label effects on current vs potential users separately.