Teenagers who have experienced a traumatic brain injury are much more likely to engage in a wide range of risky behaviors, Canadian researchers report.
Both boys and girls were more likely to smoke, use drugs, drink alcohol and get poor grades after they endured a blow to the head that knocked them out for longer than five minutes or landed them in the hospital for a day or more, the study found.
"This is a wake-up call. Concussions are brain injuries, and we need parents and physicians to become more vigilant," said lead author Gabriela Ilie, a postdoctoral fellow at St. Michael's Hospital in Toronto. "Our brains define who we are, and a lot of our behaviors and thoughts and emotions depend on our brain circuitry operating properly."
However, the study only showed an association between traumatic brain injury and risky behaviors, not a cause-and-effect relationship, noted Dr. Anthony Alessi, a neurologist and concussion expert in Norwich, Conn.
Alessi said he is concerned that studies like these provide an easy excuse for bad personal choices.
"There are plenty of people who get hit in the head who have done very well for themselves," Alessi said. "I would hate for people to think once you've had a traumatic brain injury, you automatically will have all these other problems."
For their study, the Canadian researchers used data gathered during the 2011 Ontario Student Drug Use and Health Survey developed by the Center for Addiction and Mental Health in Toronto.
The survey, one of the longest ongoing school surveys in the world, contains responses from more than 9,000 students between grades 7 and 12 in public schools across Ontario.
The survey screened for traumatic brain injury by asking teens if they ever had a head injury that resulted in a loss of consciousness for at least five minutes or required them to spend at least one night in the hospital, Ilie said.
Girls and boys appear to react differently to brain injury, Ilie and her colleagues found.
Boys were three and a half times more likely to have bad grades, three times more likely to need medical treatment for a physical injury and twice as likely to use pot, compared with other boys who hadn't had a brain injury.
Meanwhile, girls were nearly four times more likely to have bad grades and three times more likely to smoke, compared to girls without a brain injury.
Female teens were more likely to engage in a wider range of risky behaviors following a brain injury than males, Ilie said.
For example, they were more likely to smoke cigarettes, endure bullying, think about suicide or suffer from anxiety or depression following their injury -- risks that were not associated with boys who had a brain injury.
"Both boys and girls were more likely to engage in a variety of harmful behaviors if they reported a history of TBI, but girls engaged in all 13 harmful behaviors we looked for, whereas boys were at higher risk of engaging in only nine," Ilie said. "Sex matters when it comes to traumatic brain injuries."
Researchers found that risks for some behaviors grew worse with age. For example, boys with a traumatic brain injury were twice as likely to smoke daily as they entered late adolescence. The number of girls using alcohol increased 20 percent as they left middle adolescence, reaching 89 percent between ages 17 and 20.
Dr. Sam Gandy, a professor of neurology and psychiatry at the Icahn School of Medicine at Mount Sinai in New York City, noted that one part of the brain is particularly vulnerable to injury.
"The frontal lobes are especially prone to damage in head trauma," Gandy said. "This is the brain region that exerts inhibitory influences so that we maintain proper decorum. Frontal lobe damage, by removing this inhibitory influence, can lead to inappropriate sexual behavior, mood swings [both mania and depression], and violence [including suicide or homicide]. The effect of head injury on behavior is indirect, but the link is very well described."
Ilie recommended that parents consult with a head injury clinic if their child has suffered a traumatic brain injury, to learn how to monitor their condition and respond to difficulties involving problem solving, memory or emotion.
"Let's be aware. Somebody gets a brain injury, monitor it. Don't say, 'It was just a concussion,'" Ilie said.
The findings are published Sept. 30 in the online journal PLOS ONE.