Toronto, ON, November 6, 2025 – Adults diagnosed with a concussion may be at about 50 per cent higher risk of a subsequent traffic crash, finds a new study from researchers at ICES and Sunnybrook Research Institute.
Concussions can temporarily affect brain function, with symptoms including insomnia, dizziness, depression, brain fog, and slowed reaction times that can linger for weeks. These symptoms could alter driving skills and increase the risk of a motor vehicle accident.
"I worry that sometimes a concussion requires more recovery time than most people realize," says Dr. Donald Redelmeier, scientist at ICES and Sunnybrook Research Institute. "Rushing things might lead to another injury including a life-threatening traffic crash."
Key findings:
- The increased risk of a traffic crash is particularly high during the first four weeks after a concussion.
- The overall traffic risks increased further with repeated concussions.
- The traffic risks also applied to pedestrians crossing the street.
- Of the 425,158 adults diagnosed with a concussion in the study, one in 13 patients were injured in a subsequent traffic crash.
- The increased risk accounted for 1,633 total ambulance calls, 59,978 days in hospital, and $835 million in medical costs.
Some limitations of the study include the lack of data on concussion severity, as well as other factors that predispose patients to concussions as well as contribute to traffic crashes. While the findings cannot establish cause and effect, concussions can lead to symptoms that increase the risk of a serious traffic crash.
"These results highlight the importance of traffic safety following a concussion as well as preventing concussions in the first place," says Robert Tibshirani, a professor of statistics at Stanford University and also a co-author of the study.
The researchers recommend patients treat insomnia, headaches, depression, or substance misuse and also avoid high-speed trips during late-night hours in bad weather during the first month after a concussion. Clinicians should also warn patients about road traffic safety after a concussion.
The study "Concussions and risk of a subsequent traffic crash: retrospective cohort analysis in Ontario, Canada" is in the November issue of BMJ Open.
ICES is an independent, not-for-profit research and analytics institute that uses population-based health information to produce knowledge on a broad range of healthcare issues. ICES leads cutting-edge studies and analyses evaluating healthcare policy, delivery, and population outcomes. Our knowledge is highly regarded in Canada and abroad and is widely used by government, hospitals, planners, and practitioners to make decisions about healthcare delivery and to develop policy. For the latest ICES news, follow us on BlueSky and LinkedIn: @ICESOntario
Sunnybrook Research Institute (SRI) is the research arm of Sunnybrook Health Sciences Centre, an internationally recognized academic health sciences centre fully affiliated with the University of Toronto. With well-established programs in basic and applied sciences which span across three scientific platforms and eleven clinical programs, SRI is developing innovations in care for the more than 1.1 million patient visits the hospital provides annually.
