THC labeling on cannabis products: an experimental study of approaches for labeling THC servings on cannabis edibles

BACKGROUND: Over-consumption is a common adverse outcome from cannabis edibles. States such as Colorado require each serving of cannabis edible to carry a THC symbol. This study aimed to test whether packaging edibles in separate servings and/or indicating the THC level per serving improves consumer understanding of serving size. METHODS: An 3 × 2 experimental task was conducted as part of the 2019 International Cannabis Policy Study online survey. Respondents from Canada and the US (n = 45,504) were randomly assigned to view an image of a chocolate cannabis edible. Packages displayed THC labels according to 1 of 6 experimental conditions: packaging (3 levels: whole multi-serving bar; individual chocolate squares; separately packaged squares) and THC stamp (2 levels: stamp on each square vs. no stamp). Logistic regression tested the effect of packaging and THC stamp on odds of correctly identifying a standard serving, among edible consumers and non-consumers separately. Edible consumers were also asked about their awareness of a standard THC serving. RESULTS: Only 14.6% of edible consumers reported knowing the standard serving of THC for cannabis edibles. In the experimental task, among non-consumers who saw stamped bars, the multi-serving bar (AOR = 1.16 (1.08, 1.24) p < 0.001) and individually packaged squares (AOR = 1.08 (1.01, 1.16), p = 0.031) elicited more correct responses than individual squares. There was no difference in packaging formats when stamps were absent (p > 0.05 for all). Among edible consumers, there was no effect of the packaging (p = 0.992) or stamp manipulation (p = 0.988). Among both edible consumers and non-consumers, respondents in US states with legal recreational cannabis performed better than Canadians (p < 0.001). CONCLUSIONS: Regulations that require THC information to be stamped or indicated on each serving of cannabis edible may facilitate understanding of how much to consume, especially among novice consumers. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s42238-022-00124-1.