To the Editor: Brubacher et al. (Jan. 13 issue)1 conducted a methodologically rigorous study that documented increases in the prevalence of injured drivers testing positive for tetrahydrocannabinol (THC) after the legalization of recreational cannabis use in Canada. Although this study is an important contribution to the literature, we believe that the findings, which cover the first 18 months after legalization, could be better contextualized within the enormous expansion of the cannabis retail market in British Columbia since the conclusion of the study. The legal cannabis retail market in British Columbia during the study period was constricted by major product shortages2 . . .