Fatal motor vehicle collisions and associated deaths from 2007 to 2018 in United States jurisdictions with legalized recreational cannabis
| Event | No. of events | Person-years of observation | Rate per 100 000 person-years (95% CI) | IRR (95% CI) | |
|---|---|---|---|---|---|
| Crude | Adjusted* | ||||
| Recreational cannabis legalization (11 jurisdictions)†‡ | |||||
| Fatal motor vehicle collision | 73 982 | 924 545 813 | 8.00 (7.94–8.06) | ||
| No legalization | 56 866 | 717 561 813.4 | 7.92 (7.86–7.99) | 1.00 (reference) | 1.00 (reference) |
| Legalization | 17 116 | 206 983 999.6 | 8.27 (8.15–8.39) | 1.05 (0.99–1.12) | 1.15 (1.06–1.26) |
| Death from motor vehicle collision | 80 402 | 924 545 813 | 8.70 (8.64–8.76) | ||
| No legalization | 61 822 | 717 561 813.4 | 8.62 (8.55–8.68) | 1.00 (reference) | 1.00 (reference) |
| Legalization | 18 580 | 206 983 999.6 | 8.98 (8.85–9.11) | 1.04 (0.98–1.11) | 1.16 (1.06–1.27) |
| Opening of recreational cannabis dispensaries (7 jurisdictions)†§ | |||||
| Fatal motor vehicle collision | 60 518 | 774 128 598 | 7.82 (7.76–7.88) | ||
| No open dispensaries | 50 275 | 653 841 729.2 | 7.69 (7.62–7.76) | 1.00 (reference) | 1.00 (reference) |
| Open dispensaries | 10 243 | 120 286 868.8 | 8.52 (8.35–8.68) | 1.08 (1.03–1.14) | 1.18 (1.06–1.32) |
| Death from motor vehicle collision | 65 835 | 774 128 598 | 8.50 (8.44–8.57) | ||
| No open dispensaries | 54 685 | 653 841 729.2 | 8.36 (8.29–8.43) | 1.00 (reference) | 1.00 (reference) |
| Open dispensaries | 11 150 | 120 286 868.8 | 9.27 (9.10–9.44) | 1.08 (1.03–1.14) | 1.18 (1.06–1.32) |
Note: CI = confidence interval, IRR = incidence rate ratio.
↵* Adjusted for calendar year, modelled as a continuous variable.
↵† See Appendix 1, Supplemental Tables S1–S4 (available at www.cmajopen.ca/content/9/1/E233/suppl/DC1) for jurisdiction-specific event rates.
↵‡ The variance inflation factor for calendar year and legalization status ranged from 1.02 in Michigan to 4.03 in Colorado and Washington (Appendix 1, Supplemental Table S5).
↵§ The variance inflation factor for calendar year and open dispensary status ranged from 1.02 in Michigan to 3.76 in Colorado (Appendix 1, Supplemental Table S5).