Teenagers who have suffered a traumatic brain injury are twice as likely to drink alcohol or use drugs when compared with whose who have never experienced a similar blow or trauma to the head.

That’s according to a study of Ontario high school students that was published Wednesday in The Journal of Head Trauma Rehabilitation. It was led by researchers at St. Michael’s Hospital and the Centre for Addiction and Mental Health (CAMH).

“There’s a toxic combination of substance use and brain injury that needs to be recognized by people who deal with teenagers, and we need to do things to prevent both of them,” Dr. Michael Cusimano, a neurosurgeon at St. Michael’s, told the Star.

“If they sustain the injury, or are involved with drugs or alcohol, we need to treat those effectively,” says Cusimano, also a researcher at the hospital’s Keenan Research Centre for Biomedical Science. “We can’t just treat the alcohol (issue) without treating the brain injury, and we can’t treat the brain injury without addressing the alcohol and drug issue.”

For years, Cusimano noticed this toxic combination in many of his young patients. They had either sustained a head injury while drinking or high on drugs; or were injured — for instance, while playing sports — and subsequently developed substance abuse problems.

Curious about whether this was part of a more widespread phenomena, hospital researchers teamed up with experts at CAMH, which is responsible for the Ontario Student Drug Use and Health Survey, one of the longest-running school surveys worldwide. For the first time, the 2011 survey asked about traumatic brain injury, defined as any hit or blow to the head that resulted in being knocked out for at least five minutes or spending at least one night in the hospital.

Data from that survey was used in the study. Experts pored over responses of 6,383 teens in Grades 9 to 12, considered representative of all Ontario students in those grades. About 20 per cent said they had suffered a brain injury in their lifetime. Among this group, the odds of substance use were significantly greater.

For instance, when asked about drug use in the past year, those who had suffered a brain injury were: 3.8 times more likely to have used crystal meth; 3.8 times more likely to have used nonprescribed tranquilizers or sedatives; 2.8 times more likely to have used Ecstasy; 2.7 times more likely to have used nonprescribed opioid pain relievers; and 2.5 times more likely to have used cocaine.

These teens were also 2.5 times more likely to smoke cigarettes; and twice as likely to smoke pot and binge drink, meaning they would consume five or more beverages in one sitting.

They were also more likely than youth without a history of brain injury to show early signs of addiction. The data, however, did not reveal what came first: the substance use or brain injury.

Combining the effects of a brain injury — they include cognitive dysfunction, anxiety, depression, poor academic performance and suicidal thoughts — with drug use, is a dangerous mix for youth, says Robert Mann, senior scientist at CAMH.

“Their brains are still developing and their lives are too,” says Mann, also the director of the student survey. “What they’re doing as adolescents will shape the rest of their lives, so if you derail that process that can have serious consequences that last the rest of their lives.”

“We need to take (brain injuries) very seriously. Often times, there’s a tendency to shrug it off and say, ‘I hit my head, but I’m OK.’ And that may not be the case.

“Also, we need to be vigilant when these injuries occur for the possibility of other serious problems, such as heavy substance use and substance-related problems.”