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HomeHarm ReductionCannabis legalisation has not led to increased traffic injuries in Canada

Cannabis legalisation has not led to increased traffic injuries in Canada

When Canada implemented cannabis legalisation in 2018, there was concern about increased traffic harms, especially among youth. But research by the University of Northern British Columbia and others, which studied 250,000 reports of traffic-related injuries, found that legalisation has not resulted in increased injuries among all drivers or youth drivers.

It has been more than three years since Canada legalised recreational marijuana, writes Oli Herrera for CKPGToday. Along with it, only a handful of countries and some American states allow recreational use.

Prior to the country going green, a big concern was the affect it would have on drivers – especially younger ones. But the study has found that immediately following the legalisation of cannabis, there has not been an increase in traffic-related injuries due to impaired driving.

“That went contrary to my expectations. I thought those patterns would go up,” said lead research Dr Russ Callaghan of the University of Northern British Columbia (UNBC).

The study was a collaboration between UNBC, the Centre for Addiction and Mental Health (CAMH) in Toronto, the University of Victoria and Dalhousie University, according to the CKPGToday story published on 12 November 2021.

The study gathered data from hospitals in Alberta and Ontario. Both provinces record 100% of emergency room admissions in a public database. The study used more than 250,000 reports of traffic-related injuries from adult drivers and youth drivers from 2015 to 2019.

In Alberta, youth drivers are classified as 14-17 years old. In Ontario, youth drivers are 16-18 years old. Of the 52,752 reported injuries (adult drivers) in Alberta, results shows that there was only an increase of 9.17 visits. Of the 186,921 reported injuries (adult drivers) in Ontario, there was only an increase of 28.93 visits.

“Really what I wanted to do was assess some of the major indicators that could contribute to this parliamentary review and also help the public understand what the consequences of this legislation might be,” said Callaghan, as reported by CKPGToday.

Callaghan says this is just one of many studies that are needed to truly understand the impact of legalised cannabis.

“It doesn’t mean that the legalisation didn’t have an impact on traffic. There are a range of traffic harms, you can have traffic-related mortalities and you could have collisions and so on,” said Callaghan.

He said that strict federal impaired-driving laws such as Bill C-46 may have played a role for the lack of correlation. Fatal accidents is the next area that Callaghan plans to examine.


Study details

Canada’s cannabis legalization and drivers’ traffic-injury presentations to emergency departments in Ontario and Alberta, 2015-2019

Russell C Callaghan, Marcos Sanches, Julia Vander Heiden, Mark Asbridge, Tim Stockwell, Scott Macdonald, Bronwen Hughes Peterman and Stephen J Kish.

Author affiliations: University of Northern British Columbia, Centre for Addiction and Mental Health (CAMH) in Toronto, University of Victoria and Dalhousie University.

Published by Drug and Alcohol Dependence, Volume 228, on 1 November 2021.



Worldwide momentum toward legalisation of recreational cannabis use has raised a common concern that such policies might increase cannabis-impaired driving and consequent traffic-related harms, especially among youth. The current study evaluated this issue in Canada.


Utilizing provincial emergency department (ED) records (1 April 2015 to 31 December 2019) from Alberta and Ontario, Canada, we employed Seasonal Autoregressive Integrated Moving Average (SARIMA) models to assess associations between Canada’s cannabis legalisation (via the Cannabis Act implemented on 17 October 2018) and weekly provincial counts of ICD-10-CA-defined traffic-injury ED presentations.

For each province (Alberta/Ontario), SARIMA models were developed on two driver groups: all drivers, and youth drivers (aged 14-17 years in Alberta; 16-18 years, Ontario).


There was no evidence of significant changes associated with cannabis legalization on post-legalization weekly counts of drivers’ traffic-injury ED visits in: (1) Alberta, all drivers (n = 52,752 traffic-injury presentations), an increase of 9.17 visits (95 % CI -18.85; 37.20; p = 0.52); (2) Alberta, youth drivers (n = 3265 presentations), a decrease of 0.66 visits (95 % CI -2.26; 0.94; p = 0.42); (3) Ontario, all drivers (n = 186,921 presentations), an increase of 28.93 visits (95 % CI -26.32; 84.19; p = 0.30); and (4) Ontario, youth drivers (n = 4565), an increase of 0.09 visits (95 % CI -6.25; 6.42; p = 0.98).


Implementation of the Cannabis Act was not associated with evidence of significant post-legalisation changes in traffic-injury ED visits in Ontario or Alberta among all drivers or youth drivers, in particular.


CKPGToday story – New study finds no association with legalized cannabis and traffic injuries (Open access)


University of Northern British Columbia news release – Study finds no increase in traffic injuries after cannabis legalization (Open access)


Drug and Alcohol Dependence journal article – Canada’s cannabis legalization and drivers’ traffic-injury presentations to emergency departments in Ontario and Alberta, 2015-2019 (Restricted access)


See also from the MedicalBrief archives


Safe driving: Cannabis intoxication not reliably measured by field tests, THC levels


Increase in fatal traffic crashes on annual US cannabis celebration


Luxembourg first in Europe to legalise cannabis; Canada sees mostly good results


Expert opinion divided over health impacts as SA legalises dagga




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