Researchers at the University of Toronto have released the results of a study of the incidence of suicide in 236,000 concussion patients followed over a 20 year period.  The findings, reported in the Canadian Medical Association Journal, show three time the risk of suicide in patients with a history of concussion than in the general population. The increased risk of suicide applied regardless of the patients’ demographic characteristics, became accentuated over time and exceeded the risk among military personnel. In an effort to explain these findings, the authors note that:

Past studies have suggested that a concussion can cause lasting deficits through change in physiology (e.g., disrupted serotonin pathways,) mood (e.g., post- traumatic stress disorder) or behavior (e.g., disinhibition with impulsivity.)

Needless to say, one of the limitations of the study is that it does not permit definitive conclusions concerning causation. For example, as the authors point out, a concussion might indicate a latent predisposition toward suicide before the injury or worsening neurodegenerative deficits that precipitated the injury. These alternative explanations, however, seem unlikely.  The importance of this study is that concussions have often been neglected based on the popular belief that symptoms resolve quickly, leave nothing on medical imaging and require no follow up, either medically or psychologically.

This study highlights the importance of paying more attention to the potential long term implications of concussion, taking further steps to avoid concussion, and considering the potential implications of concussion in providing ongoing medical and psychological care.