Teenagers who have had a concussion also have higher rates of suicide attempts

They are also more likely to become bullies themselves, to have sought counseling through a crisis help-line or to have been prescribed medication for anxiety, depression or both, said Dr. Gabriela Ilie, lead author of the study and a post-doctoral fellow at St. Michael's Hospital.

They have higher odds of damaging property, breaking and entering, taking a car without permission, selling marijuana or hashish, running away from home, setting a fire, getting into a fight at school or carrying or being threatened by a weapon, she said in a paper published today in the journal PLOS ONE.

Dr. Ilie said the study provides the first population-based evidence demonstrating the extent of the association between TBI and poor mental health outcomes among adolescents.

"These results show that preventable brain injuries and mental health and behavioral problems among teens continue to remain a blind spot in our culture," Dr. Ilie said. "These kids are falling through the cracks."

The data used in the study was from the 2011 Ontario Student Drug Use and Health Survey developed by the Centre for Addiction and Mental Health. The survey, one of the longest ongoing school surveys in the world, contains responses from almost 9,000 students from Grades 7-12 in publicly funded schools across Ontario. The OSDUHS began as a drug use survey, but is now a broader study of adolescent health and well-being. Questions about traumatic brain injury were added to the survey for the first time in 2011.

"We know from a previous study based on OSDUHS data that as many as 20 per cent of adolescents in Ontario said they have experienced a traumatic brain injury in their lifetime," said Dr. Robert Mann, senior scientist at CAMH and director of the OSDUHS. "The relationship between TBI and mental health issues is concerning and calls for greater focus on prevention and further research on this issue."

Dr. Ilie said the teenage years are already a turbulent time for some, as they try to figure out who they are and what they want to be. Since a TBI can exacerbate mental health and behavioural issues, she said primary physicians, schools, parents and coaches need to be vigilant in monitoring adolescents with TBI.

In addition, she said many TBI experienced by youth occur during sports and recreational pursuits, and are largely preventable through use of helmets and the elimination of body checking in hockey.

The study found that adolescents who had suffered a TBI sometime in their life had twice the odds of being bullied at school or via the Internet and almost three times the odds of attempting suicide or being threatened at school with a weapon compared to those without a TBI.