A Canadian study on head injury in teens has gained worldwide attention this week.

According to the study, one in five students in grades 7 to 12 say they have suffered a head injury. Close to 6% reported an injury in the past year serious enough to knock them out for more than five minutes or require hospitalization. A little over half of these were sports-related.

The study also found a link to alcohol and marijuana, finding users more at risk of head injury.