Norm-Based Messages and Cannabis Choices in the Context of Emerging Drug Trends: A Discrete Choice Experiment in France and Italy

Abstract Background Norm-based communication interventions are increasingly used in cannabis prevention, yet evidence remains limited regarding how different normative messages influence cannabis-related preferences. This study examines whether exposure to norm-based messages affects cannabis product preferences and identifies strategies most effective in reducing preferences for THC products. Methods An online survey incorporating a discrete choice experiment was conducted among 2,001 adults in France (n = 1,001) and Italy (n = 1,000). Participants were randomly assigned to one of five video-based normative messages or a control condition. The experiment assessed preferences for cannabis products varying in type (CBD versus THC), price, payment method, vendor reputation, sales volume, and product ranking. Regression models estimated differences in THC selection probabilities across conditions. Results Four normative messages, highlighting a shift towards CBD use, approval of CBD use, disapproval of THC use, or legal prohibition, significantly reduced the adjusted probability of selecting THC products by 5.6-7.3 percentage points compared with the control condition (odds ratios approximately 0.72-0.78). The message emphasising declining THC consumption showed no statistically significant effect (OR = 0.97). Discussion The findings demonstrate that different normative messages do not produce equivalent effects on cannabis-related preferences. Messages emphasising alternative products, social approval or disapproval, and legal restrictions were associated with lower THC preferences, whereas communicating declining consumption trends was not. This distinction highlights the relevance of message content and framing for cannabis-prevention communication. Conclusions Brief, video-based normative messages can influence stated cannabis product preferences, although their effectiveness varies across formulations. Prevention interventions should therefore prioritise testing specific communication strategies rather than assuming that all normative messages are equally effective. These findings provide experimental evidence to inform the development and evaluation of targeted cannabis-prevention interventions