In an experiment with 533 Colombian participants, pictorial health warnings with yellow backgrounds on cannabis products were most effective at decreasing product appeal, reducing interest in trying cannabis, and increasing harm perception.
Cannabis regulators designing packaging requirements; public health professionals developing harm reduction communications.
Graphic yellow warnings most effective at reducing cannabis product appeal
What the researchers found
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.
Why it matters
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.
The numbers in context
533 participants. 5 conditions: no warning, text-only white, text-only yellow, pictorial white, pictorial yellow. Pictorial yellow outperformed all others on appeal, harm perception, and interest. Most effective themes: mental health, smoke toxicity, aesthetic implications, traffic accidents.
How the study worked
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.
What this study cannot tell us
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.
How to read the evidence
Randomized experiment with appropriate control conditions, though online setting and hypothetical purchase decisions limit real-world generalizability.
When this study was published
2024 study
The bigger picture
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.
Questions still open
- Do these warning effects persist with repeated exposure? Would similar designs work in markets where cannabis is already legal and normalized?
Common questions
Do warning labels actually work for cannabis?
Why was yellow background more effective?
Read the original research
Health warning labels on cannabis products. What is the best design?
The International journal on drug policy, 126, 104355
Citation
Gantiva, Carlos; Illidge-Cortes, Joseph; González-Millares, Danna; Maldonado-Hoyos, Valentina; Valencia, Laura. (2024). Health warning labels on cannabis products. What is the best design?. The International journal on drug policy, 126, 104355. https://doi.org/10.1016/j.drugpo.2024.104355