Ontario students between Grades 9 and 12 who said they had a traumatic brain injury in their lifetime, also reported drug use rates two to four times higher than peers with no history of TBI, according to research published today in The Journal of Head Trauma Rehabilitation.

"Overall, a teen with a history of TBI is at least twice as likely as a classmate who hasn't suffered a brain injury to drink alcohol, use cannabis or abuse other drugs," said Dr. Michael Cusimano, co-principal investigator of the study and a neurosurgeon at St. Michael's Hospital. "But when you look at specific drugs, those rates are often higher."

The research showed that, in the past 12 months, teens with a history of TBI said they were:

3.8 times more likely to have used crystal meth

3.8 times more likely to have used non-prescribed tranquilizers or sedatives

2.8 times more likely to have used Ecstasy

2.7 times more likely to have used non-prescribed opioid pain relievers

2.6 times more likely to have used hallucinogens

2.5 times more likely to have used cocaine

2.5 times more likely to have used LSD

2.1 times more likely to have used non-prescribed ADHD drugs

"On top of the other health consequences, substance abuse increases the odds of suffering an injury that could result in a TBI," said Dr. Cusimano, who is also a researcher with the Keenan Research Centre for Biomedical Science. "And using some of these substances may also impair recovery after injury."

Teens with a self-reported history of TBI also reported they were 2.5 times more likely to have smoked one or more cigarettes daily over the past 12 months and nearly twice as likely to have binge drank -- consuming five or more drinks in one sitting -- in the past four weeks.

Researchers defined TBI as any hit or blow to the head that resulted in the teenager being knocked out for at least five minutes or spending at least one night in hospital due to symptoms associated with the head injury. Some of these brain injuries could have been also called concussions, which are mild to moderate forms of TBI.

"Some people think of concussions as a less alarming injury than a mild TBI but this is wrong," said Dr. Cusimano. "Every concussion is a TBI. People should take every brain injury seriously because, as this research shows, the immediate and long-term effects can alter lives."

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 is one of the longest ongoing school surveys in the world. 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.

The study looked at reported substance use among 6,383 Ontario students in Grades 9 through12. Data allowed researchers to determine the substance use habits and history of TBIs among students but did not allow researchers to determine whether substance use or brain injury came first.

"These data show us that there are important links between adolescent TBI and substance use," said Dr. Robert Mann, co-principal investigator of the study, senior scientist at CAMH and director of the OSDUHS. "While we can't yet say which one causes the other, we know this combination of factors is something to watch because it can have a serious negative impact on young people as they develop."

Dr. Mann said the relationship between TBI and substance use is concerning and calls for greater focus on prevention. "In terms of our research, the next step is to get a better understanding of the direction of these behaviours and to hopefully pinpoint when and how this relationship starts."