Concussions are now known to be much more serious injuries than once thought. And the danger may not be limited to the immediate repercussions. Researchers have already linked more severe traumatic brain injury to later suicide—particularly in military veterans and professional athletes—and have more recently explored the connection between concussion and depression.
Now, new research published in the Canadian Medical Association Journal shows that even mild concussions sustained in ordinary community settings might be more detrimental than anyone anticipated; the long-term risk of suicide increases threefold in adults if they have experienced even one concussion. That risk increases by a third if the concussion is sustained on a weekend instead of a weekday—suggesting recreational concussions are riskier long-term than those sustained on the job. “The typical patient I see is a middle-aged adult, not an elite athlete,” says Donald Redelmeier, a senior scientist at the University of Toronto and one of the study’s lead authors. “And the usual circumstances for acquiring a concussion are not while playing football; it is when driving in traffic and getting into a crash, when missing a step and falling down a staircase, when getting overly ambitious about home repairs—the everyday activities of life.”
Although the underlying causes of the connection between concussion and suicide are not yet known, Redelmeier says that there were at least three potential explanations. A concussion may be a marker but not necessarily a mechanism of subsequent troubles—or, in other words, people who sustain concussions may already have baseline life imbalances that increase their risks for depression and suicide. “But we also looked at the subgroup of patients who had no past psychiatric history, no past problems, and we still found a significant increase in risk. So I don’t think that’s the entire story,” he notes. One of the more likely explanations, he says, is that concussion causes brain injury such as inflammation (as has been found in some studies) from which the patient may never fully recover. Indeed, a study conducted in 2014 found that sustaining a head injury leads to a greater risk of mental illness later in life. The other possibility is that some patients may not give themselves enough time to get better before returning to an ordinary schedule, leading to strain, frustration and disappointment—which, in turn, may result in depression and ultimately even suicide.
Lea Alhilali, a physician and researcher at the Barrow Neurological Institute who did not participate in this study, uses diffusion tensor imaging (an MRI technique) to measure the integrity of white matter in the brain. Her team has found similarities between white matter degeneration patterns in patients with concussion-related depression and noninjured patients with major depressive disorder—particularly in the nucleus accumbens, or the “reward center” of the brain. “It can be difficult to tease out what’s related to an injury and what’s related to the circumstances surrounding the trauma,” Alhilali says. “There could be PTSD, loss of job, orthopedic injuries that can all influence depression. But I do believe there’s probably an organic brain injury.”
– Jordana Cepelewicz
Read more: A Single Concussion May Triple the Long-Term Risk of Suicide
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