A crude approach to evaluating cannabis legalization
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* Zach Walsh

The proposal, made by Dr. Kelsall in her recent editorial on cannabis leglization,1 that “any increase in use … be viewed as a failure of this legislation” is flawed. From a methodological perspective, using a single index is blunt and likely to miss the mark. To make matters worse, the criterion of “any increase” is not carefully operationalized. Increased prevalence? Quantity? Frequency? What if one increases while another decreases? Is it a failure if adult use increases while adolescent use decreases?

The principle of harm reduction is recognized by the Canadian Medical Association and countless eminent health organizations. A tenet of harm reduction is that interventions be evaluated for their effects on substance-related harms rather than solely on rates of use. Through quality control, standardization of products and reducing interaction with illegal markets, legalization will likely reduce harms for the millions of Canadian adults who choose to use cannabis. Perhaps more importantly, converging evidence suggests a potential role for cannabis in addressing the opioid epidemic. Would an increase in cannabis use related to substitution for opiods such as fentanyl constitute a legislative failure?

By ignoring harm reduction, the editorial situates itself outside of the mainstream of research on substance use and discourse on drug policy. A plethora of careful reports over the past half century has proposed cannabis legalization in the name of harm reduction. The Canadian health research community has a unique opportunity to carefully test these claims. But we will not get there by simply measuring rates of use. The world is watching. Let’s get it right.

## Footnotes

*   **Competing interests:** Zach Walsh is the lead investigator for academic research studies that are funded in part by Tilray and Doja Cannabis Company (licensed producers of cannabis).

## Reference

1.  Kelsall D. Watching Canada’s experiment with legal cannabis. CMAJ 2018;190:E1218.
    
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