Assessing the public health impact of cannabis legalization in Canada: core outcome indicators towards an 'index' for monitoring and evaluation.

The legalization of non-medical cannabis use and supply is impending in Canada. This constitutes a major policy change with the declared objective of improving public health outcomes, which requires rigorous monitoring and evaluation. While numerous different aspects associated with legalization will be examined, a focused perspective is required for effective policy evaluation purposes. To these ends, we have identified a set of 10 core indicators associated with cannabis-related risk/harm outcomes-based on current best evidence-that are expected to measure the primary impacts of legalization on public health outcomes. We briefly review these indicators, and their respective data availability in Canada. As ideally an integrated outcome assessment of cannabis legalization's impact on public health will be available, we further propose options to merge the individual indicators into an integrated, weighted 'index', considering their expected relative impact for public health. One possible approach to undertake this is 'multi-criteria decision analysis' as a method to weight the relative indicator impact on public health; alternative approaches are proposed. The integrated 'public health index' for cannabis legalization will allow for scientifically comprehensive, while focused, monitoring and evaluation of the effects of legalization in Canada for the benefits of science and evidence-based policy alike.