Do Mandatory Health Warning Labels on Consumer Products Increase Recall of the Health Risks of Cannabis?

Introduction Warning labels are an important source of health information. This study examined awareness of health warnings on cannabis packages over time in Canada-where large rotating messages are mandated-versus US states with legal adult-use cannabis, which have less comprehensive regulations. Methods Repeat cross-sectional data were collected from the International Cannabis Policy Study online surveys among past 12-month cannabis consumers in Canada and the US (n = 38,448). Free recall of warning messages was assessed in 2018-2020, followed by a prompted recognition task (2020 only). Adjusted logistic regression models tested differences in free recall and recognition of warnings between Canada and US states with and without legal adult-use cannabis ("legal" and "illegal" states, respectively). Results Free recall of >= 1 warning increased to a greater extent in Canada from 2018 (5%; pre-legalization) to 2019 (13%; post-legalization) compared to US "legal" (AOR = 1.93, p < 0.001) and "illegal" states (AOR = 1.80, p = 0.007), and from 2018 to 2020 (5% vs. 15%) compared to US "legal" states (AOR = 2.23, p = 0.027). In all jurisdictions, free recall of warnings was higher among more frequent consumers (p < 0.001) and those who purchased products from legal retail stores/websites (p < 0.001). With few exceptions, when a specific message was mandated (e.g., impaired driving), consumers were more likely to both freely recall and recognize that message (all p < 0.05). Conclusions Cannabis legalization is associated with greater recall of health warning messages. Awareness of specific warning messages was higher in jurisdictions where the associated warning was mandated on packages, suggesting that warning labels may improve knowledge of cannabis-related health risks. Supplemental data for this article is available online at