A new Canadian study found that emergency room visits for car accidents involving marijuana (cannabis) use have increased significantly since recreational cannabis was legalized in 2018.
The study raises concerns about the impacts of legalization and the commercialization of the cannabis market on road safety.
Key Facts:
- Emergency room visits for car accidents involving cannabis increased by 475% from 2010 to 2021.
- The increase was greatest after the cannabis retail market was commercialized and expanded starting in 2020.
- Men, younger adults, and those with a history of mental health issues and substance use were most likely to be involved in these accidents.
- Alcohol-related car accidents did not increase over the same time period.
Source: JAMA Network 2023
Marijuana Legalization: Traffic Accidents & Injuries
Canada legalized recreational marijuana (cannabis) use nationwide in 2018.
Since then, the retail cannabis market has rapidly expanded, with more stores opening and new cannabis products like edibles becoming available.
There has been concern that easier access to cannabis could lead to more impaired driving and traffic injuries.
This new study examined emergency room data to see if car accidents involving cannabis changed in Ontario, Canada’s most populous province, from before legalization up until the end of 2021.
The results show a nearly 5-fold increase in the percentage of car accident emergency room visits involving cannabis over the 13 years studied.
The increase was greatest after April 2020, when Canada allowed the cannabis retail market to expand more rapidly.
The findings suggest Canada’s legalization and commercialization of cannabis may have contributed to more cannabis-impaired driving and car crashes, highlighting the need for more interventions aimed at road safety.
Examining Marijuana-Related Car Accidents Over Time
Study Design
The study was designed to compare emergency room visits for car accidents involving cannabis at three time points:
- Before cannabis legalization (January 2010 to September 2018)
- After legalization but with restrictions on cannabis retail stores and products (October 2018 to February 2020)
- After rapid expansion of the retail cannabis market, which overlapped with the COVID-19 pandemic (March 2020 to December 2021)
By dividing the study this way, the researchers could examine if cannabis-related car accidents changed following key cannabis policy shifts in Canada.
Data Sources
The researchers gathered data on all emergency room visits for car accidents in Ontario between 2010 and 2021. This included accidents involving drivers, passengers, pedestrians and cyclists.
They looked for documentation in the emergency visit records that indicated cannabis use was involved in the accident, such as diagnoses related to cannabis intoxication or mental/behavioral disorders related to cannabis use.
Key Findings
- There were over 947,000 emergency room visits for car accidents during the study period.
- Of those, 426 (0.04%) involved documented cannabis use.
- The annual rate of cannabis-related car accident emergency visits increased 475% between 2010 and 2021.
- Cannabis-related visits increased 94% after legalization with restrictions compared to before legalization.
- They increased even more, by 223%, after the cannabis market was commercialized and expanded.
- Alcohol-related accident visits increased only 9.4% over the whole study period.
These findings suggest cannabis legalization, and especially market commercialization, may have contributed to increased cannabis use before driving and car accidents.
However, the overlap with the COVID-19 pandemic during the commercialization period makes it hard to say for certain. Alcohol-related accidents did not increase much, but pandemic alcohol restrictions likely influenced this.
Characteristics of Marijuana-Related Car Accidents
The study also looked at the characteristics of car accidents involving cannabis using individual patient data.
This analysis found:
- Most cannabis-related accident visits were male (79%).
- Younger adults aged 19-21 had the highest odds of cannabis involvement.
- Those living in lower-income neighborhoods had nearly twice the odds.
- Over a quarter (27%) had a history of mental health issues or substance abuse.
- Cannabis-related visits were more severe, with higher ambulance use and hospital admission rates.
These findings identify subgroups that may benefit from targeted education and prevention efforts around cannabis-impaired driving.
Young Adults & Cannabis Use Before Driving
The high rates of cannabis involvement in car accidents among young adults are particularly concerning.
In Canada, it’s illegal for those under age 21 to have any detectable level of THC if they are driving. Yet the data shows this age group is most likely to drive after using cannabis.
Some potential reasons young adults are more likely to drive while impaired by cannabis:
- More likely to engage in risky behaviors in general
- Overestimate their ability to drive safely while high
- Don’t fully understand laws around cannabis impairment and driving
- Have less access to transportation compared to older adults
Prevention programs aimed at young drivers are clearly needed. Schools and colleges should educate students on the risks of cannabis-impaired driving. Mass media campaigns can also help spread this message.
For those under 21, the “zero tolerance” THC limit while driving should be strictly enforced. But education and social strategies are important to change social norms and perceptions around cannabis use before driving.
Lower Income Neighborhoods See More Weed-Related Accidents
The data also shows that emergency room visits for cannabis-related car accidents were nearly twice as common among those living in lower-income neighborhoods.
There are a few potential reasons behind this connection between neighborhood income and cannabis impairment in car accidents:
- Cannabis use is more common among those with lower incomes
- Lower income neighborhoods have easier access to cannabis retailers
- Public transit may be less available in lower income areas, increasing reliance on driving
- Lower income groups have been targeted heavily by cannabis industry marketing
Strategies that could help address this disparity include:
- Limiting the density of cannabis retailers in lower income neighborhoods
- Improving access to public transit
- Running public education campaigns on the risks of drug-impaired driving
- Restricting cannabis marketing campaigns targeting lower income groups
Helping Those With Substance Abuse History Avoid Marijuana-Related Car Accidents
The data shows that over 25% of those involved in cannabis-related car accidents had a recent history of mental health issues or substance abuse.
This subgroup is at very high risk for impaired driving and accidents after using cannabis or other substances. Some strategies to help them include:
- Screening for substance use disorders and mental health issues in healthcare settings
- Increased access to addiction and mental health treatment programs
- Support groups to help establish healthy social networks and routines
- Ridesharing services and free public transit passes to avoid driving after using
- Educational programs and relapse prevention skills training
With supportive services and better self-care skills, those struggling with substance use can avoid making the risky choice to drive while impaired.
More Research Needed on Cannabis Legalization & Traffic Accidents
This study provides compelling data that cannabis-impaired driving and related car accidents have been increasing in Canada after recreational legalization.
However, more research is still needed to clarify the degree to which legalization itself has contributed to this trend.
Some questions that remain include:
- How much of the increase was already happening before legalization due to changing social attitudes?
- How will road safety be affected as the legal cannabis market matures more over time?
- What impact have cannabis public education campaigns had on driving perceptions and behaviors?
- How do experiences in Canada compare to US states that have legalized recreational cannabis?
- What policy and legal changes could most effectively deter cannabis-impaired driving?
Continued monitoring of road safety indicators will be important as Canada moves forward with this major drug policy shift.
The health of Canadians depends on proactively identifying and mitigating any unintended harms of cannabis legalization.
References
- Study: Cannabis-involved traffic injury emergency department visits after cannabis legalization and commercialization
- Authors: Daniel T. Myran et al. (2023)
