Perceptions of effectiveness and believability of pictorial and text-only health warning labels for cannabis products among Canadian youth

Background: Health warnings have been shown to increase knowledge and awareness of health risks, influence social norms, and reduce consumption of tobacco products. With the legalization of non-medical cannabis in Canada and other subnational jurisdictions, there is a need for empirical studies to examine the impact of cannabis health warnings on consumer perceptions and behaviour relevant to cannabis. Methods: In October 2017, a between-group experiment was conducted as part of an online survey of Canadians aged 16 to 30 years (N = 870) recruited from a national consumer panel. Participants rated the perceived effectiveness and believability of either text-only or pictorial cannabis health warnings and then completed a message recall task. Participants also reported their level of support for cannabis warnings, and support for including cessation information and a quitline on the warnings. Results: Pictorial health warnings for cannabis products were perceived as more effective and believable than text-only warnings (p < 0.001), and the superiority of pictorial warnings was found across different warnings: dose (p = 0.039), co-morbid drug use (p = 0.006), and pregnancy (p < 0.001). Pictorial warnings were also rated as more believable (p = 0.048). Overall, 87.7% respondents supported having health warnings on cannabis products, and 84.0% supported the inclusion of a quitline number on cannabis health warnings. Conclusion The current study provides the first empirical test of cannabis health warnings, consistent with the considerable body of evidence on the effectiveness of pictorial warnings on tobacco products. There was strong support for the inclusion of picture warnings and the inclusion of resources and quitlines on cannabis packaging.