TORONTO - Adults who experience a concussion appear to have a long-term suicide risk three times higher than that of the general population — and that risk rises to four times higher if the traumatic brain injury occurred on a weekend, a study suggests.
The study, published Monday in the Canadian Medical Association Journal, also found that having a subsequent concussion was associated with a further increase in the risk that a person would take his or her own life.
"We know that a concussion can cause lasting changes in the brain that can alter mood, perhaps resulting in behaviour changes, including impulsivity," said principal researcher Dr. Donald Redelmeier, an internal medicine specialist and senior scientist at Sunnybrook Health Sciences Centre in Toronto.
"It's possible that we're seeing greater suicide risk linked to weekend concussions due to risk-taking associated with recreation or misadventure, whereas weekday injuries may be linked to employment hazards."
To conduct the study, researchers analyzed Ontario health records to identify more than 235,000 concussion patients between 1992 and 2012. Over that 20-year period, 667 people with a history of concussion died by their own hands.
Those injured on weekdays accounted for 519 suicides, three times the population norm of about nine per 100,000 annually, while those whose brain injuries occurred on weekends accounted for 148 suicides, about four times the population norm.
In absolute terms, researchers concluded that 470 of these deaths might not have occurred if patients' risks had matched those of the general population.
"Patients who experienced a concussion were at increased risk of suicide regardless of demographic factors such as age, sex, socioeconomic status or past psychiatric conditions," Redelmeier said.
The mean age of patients at the time of suicide was 41, men and women were equally affected, most lived in cities, and the average time gap between the concussion and committing suicide was almost six years.
"It may not be that the concussion was the cause," Redelmeier noted. "It may be that they were already predisposed towards self-harm activity and in that way the concussion isn't a mechanism; it is a marker of an underlying tendency. And that certainly could be the case in our study.
"But it does leave this lingering question: Were they just predisposed to begin with or was there a direct injury that disrupted serotonin pathways and led to impulsivity and depression and sleep disturbances and irritability?" (Serotonin is a neurotransmitter, or brain chemical, related to mood regulation, pain perception and other physical functions.)
"The patients that I see, that's what they talk about a lot: 'I've never fully recovered from the concussion. I'm just not the same,'" he said. "For some patients with concussion, it takes so long to get better and you kind of wonder if they fully recover."
Dr. Anthony Phillips, who was not involved in the study, called it a well-conducted research paper, which shows for the first time that weekend concussions seem to carry an even higher risk of long-term suicide than do weekday concussions.
"There's reasons for this — the fact that weekend events may be related to recreation where there might be a more severe injury. It's a very interesting pattern that's never been reported before," said Phillips, scientific director of neurosciences for the Canadian Institutes of Health Research.
"There's no doubt that there are changes, scars that are left in the brain that are subtle and are producing changes in perhaps neurotransmitters or neural connections," he said Monday from Vancouver.
While stressing that the research does not suggest that every person who suffers a concussion "now has a high liability of suicide," Phillips said the increased risk needs to be taken seriously.
"We've got to protect our brains, keep them healthy," he said. "If you've had a concussion, you should take extra precautions to make sure you don't get another one. It's a matter of prevention and not putting yourself in harm's way."
Interestingly, the study found that about half the patients had visited a physician for unrelated medical issues in the week prior to taking their own lives. Overall, about 80 per cent had seen their doctors in the month prior to their suicide.
"It was a missed opportunity, at face value. A doctor may not be able to make everything perfect, but is in a position to stop a situation from becoming worse," said Redelmeier, suggesting that patients should routinely be asked about a history of concussion and suicidal thoughts.
"I think an awareness of the association between concussions and suicide is informative not just for public health, but also for practising physicians," he said.
"Understanding how a history of concussion raises the risk of suicide and supporting patients with better screening, treatment and followup for recovery may be important steps in preventing these tragic and avoidable deaths."
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