The Züri Can study: Can regulated cannabis sales promote lower-risk cannabis use? Mini-review and study protocol.

Background And Aims: Recreational use of cannabis is illegal in most countries. Despite this, it is the third most commonly used psychoactive substance worldwide. As a result of this discrepancy, a growing number of countries have begun to reassess their legal approach to cannabis in recent years. While the health risks of cannabis and potential harm reduction measures are increasingly well understood, there are still significant gaps in knowledge about which regulatory and supply models are effective in promoting lower-risk cannabis use. In this paper, we outline the Züri Can study, which implements and evaluates a regulatory framework for cannabis sales in the city of Zurich, Switzerland, between 2023 and 2026. In addition, we illustrate how the study addresses current knowledge gaps to provide further insight into the potential future regulation of cannabis in Switzerland. To embed the study in the present scientific and political context, we first provide a brief overview of the state of knowledge on cannabis-related health risks and means of reducing them, along with lessons learned from other countries that have implemented varying regulatory systems.

Design And Measurements: 2,100 participants will be able to legally purchase cannabis either at a pharmacy, a cannabis social club, or the municipal drug information center over a three-year period. As part of this observational study, participants will be evaluated regarding their cannabis use habits and motives, their knowledge of lower-risk use, and their mental and physical health, among other parameters. Established harm reduction strategies are implemented as an integral part of the study design.

Comments: The study will contribute to a better understanding of the impact of different cannabis distribution models on cannabis use patterns and related health outcomes. The results are expected to assist Swiss and international policy makers in developing evidence-based and public health-oriented regulatory frameworks for cannabis.