Among students who reported receiving poor grades in school, the likelihood of having a history of traumatic brain injury was almost four times greater than among those who received high grades. Those who reported the most frequent use of alcohol were about twice as likely to have a history of traumatic brain injury as were those who could recall no such history. And those who reported a severe blow to the head in the last year were seven times more likely to report such alcohol use than were those with no history of traumatic brain injury. Frequent cannabis use was more than four times more common among those with a recent history of traumatic brain injury than among those who had never been concussed.