Bennet Omalu is pictured on the red carpet on Dec. 9 for a screening of the movie, "Concussion." Omalu is credited with helping bring the dangers of concussions in sports into the public spotlight. (Sarah L. Voisin/The Washington Post)

Suicide and brain injury have long been linked by scientists, but just how many people who have had a brain injury end up committing suicide? A new study has a grim answer: It found that the longterm risk of suicide increases three-fold among adults who have had concussions.

That’s the conclusion of a team of Canadian researchers who studied a health insurance database of more than 235,000 people. Their work was recently published in the Canadian Medical Association Journal. Rather than focus on athletes or people who were hospitalized for days or weeks after head injuries, they looked at ordinary people who had concussions but did not sustain severe brain injury. The researchers matched those whose official death certificates listed suicide with their medical history over a 20-year period. They found a suicide rate of 31 deaths per 100,000 patients — three times the population norm. The mean time between a mild concussion and suicide was 5.7 years, and each additional concussion raised suicide risk.

There were similarities between those who suffered a mild concussion and later committed suicide. Fifty-two percent were men, 86 percent lived in an urban area, and their mean age was 41. Those of lower socioeconomic status were at higher risk, as were those who got concussions on a weekend. Patients who sustained concussions on Saturday or Sunday were four times more likely than a member of the general public to kill themselves.

“The magnitude of the increased risk surprised me,” says Donald Redelmeier, a practicing physician and professor of medicine who led the study. “I always had my doubts about whether individuals fully recover from concussions, but I never thought I’d find a three-fold increase in risk.”

The study was conducted in Canada, but Redelmeier notes that due to similarities between populations and the large cohort, studies in the United States could reveal similar risks. However, the study was limited by the data — only patients who sought medical treatment for their head injuries and who had suicide listed as a cause of death were considered.

Though researchers are gaining more insight into how many suicides may be caused by concussions, questions about a clear causal link between concussion and suicide remain. Research often focuses on massive head injuries instead of smaller, milder concussions, and scientists don’t yet understand all of the mechanisms that link damaged brain anatomy with impulsivity, suicidal thoughts and actual suicide attempts.

Redelmeier, who has long been intrigued by mild head injuries in patients who are not elite athletes or military veterans — patients who, he says, “aren’t such superstars” — thinks physicians can do better.  When prevention fails, he says, it’s up to medical practitioners to take the condition seriously. He says he was shocked at how frequently concussion patients who eventually committed suicide had come into contact with health-care professionals (about half saw a physician within the last week of life).

But there’s another factor, too: the patients themselves. Instead of getting back in the game, he says, people who have sustained concussions should give themselves time to recover and remember to consider their head injury — no matter how mild — as an important part of their medical history. “Look after your brain,” he says. “People just don’t take concussions seriously.”

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