Commercialization of cannabis linked to increased traffic injuries

Ottawa, ON, September 5, 2023 – Annual rates of emergency department visits for cannabis-involved traffic injury increased by 475 percent over 13 years, according to a new study from The Ottawa Hospital, Bruyère Research Institute, and ICES.

The study examined cannabis-involvement in emergency department (ED) visits for traffic injuries between 2010 and 2021 and looked for changes after the legalization of cannabis in October 2018 and following the commercialization of the legal market (expanded cannabis products and retail stores), which overlapped with the COVID-19 pandemic.

“Our findings highlight a concerning increase in cannabis-involvement in traffic-injury emergency visits over time, with even sharper spikes following the phases of legalization and commercialization,” says lead author and ICES post-doctoral trainee Dr. Daniel Myran, who is also a family physician and fellow at the Bruyère Research Institute and The Ottawa Hospital. “Conversely, alcohol-involvement in traffic injury ED visits did not increase over the study period, which suggests that legalization of cannabis has played an important role in rising rates.”

While documented cannabis-involvement in traffic injuries ED visits were very rare, the data raise concern about potential broader increases in cannabis-impaired driving which may have accelerated after legal market expansion. 

Published in JAMA Network Open, the researchers examined medical record data of 947,604 ED visits for traffic in in Ontario, Canada. They included records from January 2010 and December 2021, but excluded ED visits from individuals who were younger than 16 (minimum legal age of driving) at the time of the ED visit.

Key findings include:

1. The number of cannabis-involved traffic injury ED visits increased significantly. Annual rates of visits surged by 475 percent, from 0.18 visits per 1,000 total motor vehicle collisions in 2010 to 1.01 in 2021.
2. Legalization of non-medical cannabis with restrictions was associated with a 94 percent increase in the rate of cannabis-involved traffic injury ED visits compared to the pre-legalization period. The subsequent phase of commercialization, which overlapped with the COVID-19 pandemic, saw an even greater increase of 223 percent in rates compared to the pre-legalization period.
3. Male sex (assigned at birth), living in lower-income neighborhoods, being aged 19-21, and having a prior cannabis-related ED visit were associated with higher rates of ED visits.

“The observed increase in cannabis-involved traffic injuries might reflect broader trends in cannabis-impaired driving,” says Dr. Myran. “The study highlights the need for enhanced prevention efforts, including targeted education and policy measures.”

One limitation of the study is that ED staff may have been more aware of the potential for cannabis-related traffic injuries after legalization, leading to higher levels of testing for cannabis. The researchers believe that this would not have explained all the observed increase due to the severity of traffic injuries, which would be thoroughly investigated despite policy or testing procedure changes.

The authors caution that it is too soon to understand the impact of cannabis legalization on road safety particularly because of the enormous decline in driving and mobility during the pandemic, which overlapped with much of the legalization period.

The study, “Cannabis-involvement in traffic injury emergency department visits after the legalization and subsequent commercialization of non-medical cannabis” was published in JAMA Network Open.

Author block: Myran DT, Gaudreault A, Pugliese M, Manuel D, Tanuseputro P.

ICES is an independent, non-profit research institute that uses population-based health information to produce knowledge on a broad range of healthcare issues. Our unbiased evidence provides measures of health system performance, a clearer understanding of the shifting healthcare needs of Ontarians, and a stimulus for discussion of practical solutions to optimize scarce resources. ICES knowledge is highly regarded in Canada and abroad and is widely used by government, hospitals, planners, and practitioners to make decisions about care delivery and to develop policy. For the latest ICES news, follow us on Twitter: @ICESOntario

The Bruyère Research Institute supports investigators who contribute to a better, more responsive health care system that delivers the best care to patients, residents, and families. The Institute provides solutions to improve the health and health care of aging and vulnerable Canadians. To learn more, visit http://www.bruyere.org.

The Ottawa Hospital (TOH) is one of Canada’s top learning and research hospitals where we are guided by our vision to provide the world-class and compassionate care we would all want for our loved ones. Our multi-campus hospital, affiliated with the University of Ottawa, is home to the Regional Trauma Centre and Cancer Centre, and to discoveries that are adopted globally. Backed by generous support from the community, we are focused on reshaping the future of health care to improve the health of our diverse population of patients from Eastern Ontario, Western Quebec, and Nunavut. For more information about The Ottawa Hospital, visit OttawaHospital.on.ca.

The University of Ottawa is home to over 50,000 students, faculty and staff, who live, work and study in both French and English. Our campus is a crossroads of cultures and ideas, where bold minds come together to inspire game-changing ideas. We are one of Canada’s top 10 research universities—our professors and researchers explore new approaches to today’s challenges. One of a handful of Canadian universities ranked among the top 200 in the world, we attract exceptional thinkers and welcome diverse perspectives from across the globe. www.uottawa.ca