A new Canadian study is painting a frightening picture of head injuries among teenagers, finding that serious blows to the brain are occurring more often than thought.

The study found that one in five teens in Ontario has had a concussion or another brain injury in their lifetime that was serious enough to leave them unconscious for five minutes or to send them to hospital overnight.

As well, a total of 5.6 per cent reported they had had a concussion or significant brain injury in the past year.

One of the study authors, Dr. Michael Cusimano, a neurosurgeon at St. Michael’s Hospital in Toronto, says the kinds of head injuries they were studying were significant.

“These are not just little knocks on the head where they are kind of dazed and walked it off. These are more significant brain injuries,” he told CTV News. “If a person sustains several of these in the life, they can have potentially long-term effects.”

These injuries are concerning, he said, not only because the brains of teens are still developing, but because there is growing evidence that multiple brain injuries can result in lifelong consequences, such as cognitive problems, and even mental health problems.

The study used data from the 2011 “Ontario Student Drug Use and Health Survey,” which is one of the longest ongoing school surveys in the world. It uses responses from almost 9,000 students from Grades 7-12. While the study was designed to be a drug-use survey, it’s now used as a broader study of teen health, with questions about traumatic brain injury added to the survey in 2011.

The survey found that the majority of traumatic brain injuries for the teens occurred during sports: 47 per cent for girls and 63.5 per cent for boys.

Perhaps not surprisingly, hockey and soccer accounted for more than half the injuries.

The alcohol factor

Teens who said they drank alcohol occasionally/frequently over the past year had a more than five times greater risk of having had a traumatic brain injury in the past 12 months, compared to other students. Those who said they used marijuana 10 or more times a year also had a three times greater risk.

Students who reported poor grades at school (below 60 per cent) had almost four times the odds of a lifetime brain injury than students with grades at or above 90 per cent.

Cusimano said those links with alcohol, marijuana and poor grades were interesting.

“We don’t know if there is a cause and effect relationship there. We need to study that more. But this is the first time that has been described,” he said.

Gabreila Ilie, the study’s lead author and a post-doctoral fellow at St. Michael’s Hospital, says it’s important to know who is getting these brain injuries and what long-term-effects they’re having.

“Lifetime brain injuries – but not those that were experienced in the last 12 months – were associated with reported current lower grades. That’s interesting in itself,” she told Canada AM.

She added it’s important not to jump to conclusions about cause and effect. For example, it’s possible that drug and alcohol use led to brain injuries within the last year, but it’s also possible it’s the other way around.

“It could be you get a concussion or a mild traumatic brain injury and you resort to alcohol and cannabis as a way of coping with the injury,” she told Canada AM.

As for the sports-related injuries, Cusimano says a good deal of recent research has focused on such injuries and many of those reports make recommendations that he says need to be heeded.

“In soccer, for example, we know that young kids under age 9, they are running into goal posts; this is the major cause of brain injuries in that sport in that age group,” he said.

One way to reduce that risk is to use only moveable nets, or ensure that padding is installed on all goalposts, he said.

In hockey, Cusimano said there are still a significant number of injuries that are occurring from hits from behind, hits to the head or fighting.

“So we could make a big impact on that sport by having rules that are enforced strictly and rules that have significant impact, not only to the player inflicting it – that’s not enough – but also the team and the league”

With a report from CTV medical specialist Avis Favaro and producer Elizabeth St. Philip