Six months after suffering a TBI, many patients still feel depressed and anxious and some struggle with aggression and substance abuse, Manley said. “A substantial number of people seen in emergency departments with traumatic brain injuries” don’t get follow-up care afterward, he said. “So we should not be surprised that we’re seeing people who are unemployed, incarcerated.”

Matheson pointed out that her study shows an association, not a causal relationship, between TBI and incarceration. More research is needed to determine how the injuries and imprisonment connect, she said.

In 2010, TBIs were diagnosed in 2.5 million Americans, according to the U.S. Centers for Disease Control and Prevention. Over the past decade, rates of visits to U.S. emergency departments for TBI rose 70 percent, the CDC estimates.

Manley attributes the increase to greater awareness about concussions in sports but said brain injuries are just as likely to occur as a result of slips and falls. Prior studies suggested links between TBI and criminal justice involvement but the findings were not all statistically significant, the authors write. The new study is one of the largest of its kind and the first to examine the association in Canada.

Matheson called for more screening for TBI in prisoners and said correctional programs should recognize that people with brain injuries may have memory lapses and trouble sitting still. Manley stressed the need for increased awareness about the potential for debilitating long-term fallout from TBI. “There’s probably a huge hidden cost to society here, not to mention the cost to individuals and their families,” he said.