Teenagers who have suffered a concussion or other traumatic brain injury are more likely to report using alcohol and drugs compared to peers with no history of such an injury, researchers have found.

Use of non-prescribed tranquilizers and opioids as well as illicit drugs like cannabis, cocaine and even crystal meth was two to four times higher among Ontario high school students who had experienced a traumatic brain injury (TBI) than classmates who hadn't had a serious blow to the head, the researchers report in a study published Wednesday in the Journal of Head Trauma Rehabilitation.

Teens Concussion Drug Use 20141126

Dr. Michael Cusimano, a neurosurgeon and researcher in Toronto, said it's alarming how early students mix a head trauma with alcohol or drug use. (Yuri Markarov/St. Michael's Hospital/Canadian Press)

The study, which analyzed data from the 2011 Ontario Student Drug Use and Health Survey, found that one in five of the Grade 9 to 12 students reported they'd had a previous TBI.

Besides having a higher rate of alcohol and drug use, students in this group were also 2.5 times more likely to have smoked one or more cigarettes daily during the previous year and nearly twice as likely to have engaged in binge drinking — consuming five or more alcoholic drinks in one sitting — in the previous month.

"It's a really toxic combination when you have the two together," co-principal researcher Dr. Michael Cusimano said of mixing a head trauma with alcohol or drug use. "And it's alarming how early this is occurring. This is Grade 9 to Grade 12."

"We know that people who have alcohol or substance use problems don't recover as well from a brain injury," said Cusimano, a neurosurgeon at St Michael's Hospital in Toronto. "They can't participate as well in the rehab, and they don't recover their original abilities as well as people who have not been using drugs and alcohol."

As well, adolescence is an age when the brain is still developing — and having a TBI and exposing the brain to the effects of alcohol or drugs may "greatly impair" that development, he said.

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

The study looked at reported TBIs and substance use among Ontario students, using responses from a representative sample of 6,383 respondents who took part in the survey. Data allowed researchers to determine substance use habits and TBI history, but not which came first — the brain injury or the alcohol and/or drug use.

"People with these injuries may be using these substances more, but the effects of the injury may be such that it may predispose them to use the substances more often as well, " said Dr. Robert Mann, a senior scientist at the Centre for Addiction and Mental Health who co-led the study.

"On the other hand, we also know that people who are substance users may be more likely to have these kinds of injuries," said Mann. "The classic example is alcohol. Alcohol impairs psychomotor performance, so you're more likely to have an injury, perhaps more likely to have a head injury."

Injuries more common than thought

Many recreational drugs also can affect physical performance and judgment, setting up a person for potential harm, he said.

In any given year, about five per cent of teenagers will suffer a concussion or other brain injury, and about 60 per cent of them will occur while participating in sports.

"What we found in this research is that these injuries are more common than we would have thought … and that also there does appear to be a cluster with these injuries of problematic behaviour, substance abuse and mental health concerns," said Mann.

"And we know that substance use problems and mental health problems in adolescence can result in problems later on in life."

Concussions and other brain injuries can cause dizziness, confusion, memory loss, headache, nausea or vomiting.

Depending on the severity of the injury, symptoms can persist for some time. Concentration and the ability to remember may be impaired; the person can be irritable, depressed and have marked personality changes; sensitivity to noise and light, along with disturbed sleep, are also common.

Cusimano said it's possible some teens with a traumatic brain injury turn to alcohol or drugs to deal with such symptoms, trying to make themselves feel better by self-medicating.

"I think parents, coaches, teachers and guidance counsellors need to be aware of this toxic combination of drugs, alcohol and brain injury, and they need to at least inquire about [them]," he said.

"So if they have a TBI, they need to inquire about drugs and alcohol. And if they use drugs and alcohol, they need to inquire about brain injury. Both things need attention."