Traffic Injuries Grew After Marijuana Legalization: Study

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Sept. 7, 2023 – Canada’s legalization of recreational marijuana in 2018 is linked to a dramatic increase in marijuana-related traffic injuries resulting in treatment at an emergency department, a new study shows.

The researchers found that the steepest increases occurred when more types of marijuana products became available and were offered by more businesses. For comparison, researchers looked at alcohol-related traffic injuries and found there was no corresponding increase in emergency department visits during the same time period.

The findings, published Wednesday in JAMA Network Open, suggest “that legalization of cannabis has played an important role in rising rates,” lead author Daniel Myran, MD, MPH, said in a news release. Myran is a family doctor and a Canadian Institutes for Health Research fellow.

For the study, researchers analyzed data for traffic-related injuries treated at emergency departments in the Canadian province of Ontario, which is the country’s most populous province, with more than 14 million people. The study period was from January 2010 to December 2021. Traffic injuries included those involving motor vehicles or pedestrians and cyclists. Marijuana was considered an involved factor if a medical code for marijuana use was listed in the patient’s visit record.

During the 12-year study period, 426 marijuana-involved traffic injuries were treated in emergency departments. The rate of marijuana-related injuries rose from 0.18 emergency visits per 1,000 motor vehicle collisions in 2010, to 1.01 visits per 1,000 collisions in 2021. That equals a 475% increase during the entire study period.

Because the legalization of recreational marijuana in Canada involved a gradual increase in access to the drug, the researchers also compared three time periods to see whether different levels of access impacted the rate of traffic-related emergency department visits involving marijuana use. The time periods compared were the nearly 8-year period before legalization, the early legalization period of October 2018 to March 2020, and the broad commercialization period of legalization, which was April 2020 to December 2021. They found that:

  • Incidents increased 94% when comparing the period before legalization to the early legalization period.
  • Incidents increased 223% when comparing the early legalization period to the broad commercialization period.

The researchers noted that the broad commercialization period overlapped with the start of the pandemic, which involved dramatically varied driving patterns. 

Males, people ages 19 to 21 years old, and those living in lower-income neighborhoods were the most likely to visit emergency departments due to marijuana-related traffic injuries.

Canada has laws that limit the amount of the drug in a person’s blood that is allowed while driving. The study authors concluded that more education is needed in the country regarding marijuana-impaired driving, as well as more enforcement.