Article Figures & Tables
Figures
- Figure 1:
Forest plot of fatal motor vehicle collisions (A) and associated deaths (B) from 2007 to 2018 in United States jurisdictions with legalized recreational cannabis. *Adjusted for calendar year, modelled as a continuous variable. Note: CI = confidence interval, IRR = incidence rate ratio.
- Figure 2:
Forest plot of fatal motor vehicle collisions (A) and associated deaths (B) from 2007 to 2018 in United States jurisdictions with open recreational cannabis dispensaries. *Adjusted for calendar year, modelled as a continuous variable. Note: CI = confidence interval, IRR = incidence rate ratio.
Tables
- Table 1:
United States jurisdictions with regulations for legalized recreational cannabis in effect before 2019
Jurisdiction Date legalization in effect First month legalization in effect for primary analysis* Date commercial dispensaries open First month commercial dispensaries open for sensitivity analysis* Cannabis-specific impaired driving law6 Alaska7,8 Feb. 24, 2015 March 2015 Oct. 29, 2016 November 2016 None California9,10 Nov. 9, 2016 November 2016 Jan. 1, 2018 January 2018 None Colorado11,12 Dec. 10, 2012 December 2012 Jan. 1, 2014 January 2014 Reasonable inference for impairment ≥ 5 ng/mL THC† District of Columbia13 Feb. 26, 2015 March 2015 No commercial NA None Maine14,15 Jan. 30, 2017 February 2017 Oct. 9, 2020 NA None Massachusetts16,17 Dec. 15, 2016 December 2016 Nov. 20, 2018 December 2018 None Michigan18–20 Dec. 6, 2018 December 2018 Dec. 1, 2019‡ NA Zero tolerance (no detectable presence of cannabis permitted) Nevada21,22 Jan. 1, 2017 January 2017 July 1, 2017 July 2017 Per se limit ≥ 2 ng/mL THC§ Oregon23–25 July 1, 2015 July 2015 Oct. 1, 2015¶ October 2015 None Vermont26 July 1, 2018 July 2018 No commercial dispensaries NA None Washington27,28 Dec. 6, 2012 December 2012 July 8, 2014 July 2014 Per se limit ≥ 5 ng/mL THC§ Note: NA = no data available for legalized (or commercial dispensaries open) months before 2019, THC = tetrahydrocannabinol.
↵* Rounded up or down to the nearest full month of legalization (or commercial dispensaries opening, for sensitivity analysis).
↵† Reasonable inference requires that the jurisdiction must prove with other evidence, in addition to exceeding the legal THC limit, that the driver was impaired.
↵‡ On Dec. 1, 2019, existing medical cannabis dispensaries in Michigan were permitted to transfer up to 50% of their medical cannabis inventory to recreational cannabis inventory. Until November 2021, retailers must hold a medical cannabis licence in order to apply for a recreational cannabis licence.
↵§ Per se limits do not require that the jurisdiction prove that drivers were impaired in order to charge them with driving under the influence if their THC level exceeded the legal limit.
↵¶ On Oct. 1, 2015, existing medical cannabis dispensaries in Oregon were permitted to sell recreational cannabis. The first licences were issued to recreational cannabis retailers on Oct. 1, 2016.
- Table 2:
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).
- Table 3:
Fatal motor vehicle collisions and associated deaths from 2007 to 2018 in United States jurisdictions with legalized recreational cannabis, comparing the first 12 months to subsequent months
Event No. of events Person-years of observation Rate per 100 000 person-years (95% CI) IRR (95% CI) Crude Adjusted* Recreational cannabis legalization Fatal motor vehicle collision 73 982 924 545 813 8.00 (7.94–8.06) No legalization 68 180 855 020 030.8 7.92 (7.86–7.99) 1.00 (reference) 1.00 (reference) First 12 mo after legalization† 5802 69 525 782.3 8.35 (8.13–8.56) 1.01 (0.93–1.11) 1.12 (1.01–1.23) Subsequent months after legalization‡ 11 314 137 458 217.3 8.23 (8.08–8.38) 1.06 (1.00–1.13) 1.22 (1.11–1.35) First 12 mo v. subsequent months‡ – – – 0.96 (0.88–1.05) 0.92 (0.84–1.02) 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) First 12 mo after legalization† 6290 69 525 782.3 9.05 (8.83–9.27) 1.00 (0.92–1.10) 1.11 (1.00–1.24) Subsequent months after legalization‡ 12 290 137 458 217.3 8.94 (8.78–9.10) 1.06 (1.00–1.12) 1.23 (1.11–1.37) First 12 mo v. subsequent months‡ – – – 0.96 (0.89–1.04) 0.92 (0.84–1.01) Opening of recreational cannabis dispensaries 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) First 12 mo of open dispensaries† 4968 60 437 733.9 8.22 (7.99–8.45) 1.03 (0.95–1.13) 1.13 (1.03–1.24) Subsequent months of open dispensaries‡ 5275 59 849 134.9 8.81 (8.58–9.05) 1.13 (1.08–1.18) 1.34 (1.24–1.46) First 12 mo v. subsequent months‡ – – – 0.92 (0.82–1.04) 0.88 (0.76–1.02) 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) First 12 mo of open dispensaries† 5426 60 437 733.9 8.98 (8.74–9.22) 1.03 (0.95–1.13) 1.13 (1.03–1.25) Subsequent months of open dispensaries§ 5724 59 849 134.9 9.56 (9.32–9.82) 1.12 (1.07–1.17) 1.35 (1.25–1.45) First 12 mo v. subsequent months§ – – – 0.92 (0.82–1.03) 0.88 (0.76–1.01) Note: CI = confidence interval, IRR = incidence rate ratio.
↵* Adjusted for calendar year, modelled as a continuous variable.
↵† Includes up to 12 months for each jurisdiction (some jurisdictions contributed less than 12 mo, depending on their dates of legalization or opening of dispensaries).
↵‡ Excludes Michigan and Vermont (no subsequent months of legalization available).
↵§ Excludes California and Massachusetts (no subsequent months of open dispensaries available).
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