Table 3. Overall Relative Changes in Rates of Monthly CHS ED Visits Per Capita and Per All Visits in Ontario, Canada, Following Recreational Cannabis Legalization and Commercialization and the COVID-19 Pandemic.

Measure	CHS visits, incidence rate ratio (95% CI)
	Per capitaa	Per all-cause ED visits	Per all-cause vomiting visits	Per mental health visits	Per substance use visits
Prelegalization monthly slope	1.03 (1.03-1.03)	1.03 (1.03-1.03)	1.03 (1.02-1.03)	1.02 (1.02-1.03)	1.03 (1.02-1.03)
Legalization period
Immediate change	0.99 (0.87-1.12)	1.00 (0.85-1.18)	1.07 (0.90-1.28)	1.03 (0.88-1.22)	1.00 (0.85-1.16)
Gradual change	0.99 (0.98-1.00)	0.99 (0.98-1.01)	0.99 (0.97-1.00)	0.99 (0.98-1.01)	1.00 (0.98-1.01)
Monthly slope	1.02 (1.01-1.03)	1.02 (1.01-1.03)	1.01 (1.00-1.03)	1.02 (1.00-1.03)	1.02 (1.01-1.04)
Net change 17 mo after legalizationb	0.83 (0.68-1.02)	0.87 (0.66-1.15)	0.88 (0.65-1.19)	0.92 (0.71-1.19)	0.94 (0.72-1.25)
Commercialization and COVID-19
Immediate change	1.49 (1.31-1.70)	1.60 (1.37-1.87)	1.59 (1.34-1.87)	1.47 (1.26-1.72)	1.53 (1.32-1.77)
Gradual change	0.99 (0.98-1.00)	1.00 (0.98-1.01)	1.00 (0.98-1.02)	1.00 (0.99-1.02)	0.99 (0.98-1.01)
Monthly slope	1.01 (1.00-1.02)	1.02 (1.01-1.03)	1.01 (1.00-1.03)	1.02 (1.01-1.03)	1.02 (1.01-1.03)
Net change 16 mo after commercialization and COVID-19c	1.32 (1.07-1.63)	1.52 (1.12-2.06)	1.57 (1.13-2.18)	1.38 (1.04-1.82)	1.56 (1.15-2.11)

Abbreviations: CHS, cannabis hyperemesis syndrome; ED, emergency department.

^a Per capita visits include adjustment for March and April 2020, when all-cause ED visits declined during first months of COVID-19 pandemic.

^b Relative to the counterfactual secular trend from the prelegalization period.

^c Relative to the counterfactual trend from the legalization with strict control period.