An assessment of cohort, cross-sectional, and case-control studies involving more than 7 million individuals has found an association between concussions, mild traumatic brain injury (TBI), and risk of suicide.
The analysis, led by Michael Fralick, MD, SM, of the Department of Epidemiology at Harvard TH Chan School of Public Health, reiterates a clinical trend reported as recently as this summer. In August, a Denmark-based study of a similar patient population size reported that those who suffer from concussions and/or TBI face a nearly two-fold greater risk of suicide.
This newest assessment involved a systematic search of studies reported from 1963 to May 1, 2017. Investigators included 17 analyses which featured 718,572 patients diagnosed with concussion and/or mild TBI, and 6,974,124 individuals not diagnosed with either neurological condition.
Among the 17 studies, 14 included patients in North America, 2 included patients in Scandinavian countries, and 1 was conducted in Australia. Military personnel—a subpopulation popularly associated with both TBI and suicide risk—were included in 7 studies, while children from the general population were included in 3 studies.
Investigators found there to be a more than two-fold greater risk of suicide in people to be diagnosed with at least 1 concussion and/or mild TBI compared to those not diagnosed with either (RR= 2.03 [95% CI: 1.47 – 2.80] P < .001). A majority of studies also reported a heightened risk of suicide attempt following a concussion and/or mild TBI. Additionally, all 8 studies to assess risk of suicidal ideation had reported a heightened risk following concussion and/or mild TBI diagnosis.
In separate, stratified analyses comparing military personnel to civilian populations, investigators reported a higher combined estimate for studies of nonmilitary populations (RR 2.36 [95% CI: 1.64 – 3.40] P < .01) than the combined estimate for studies of military populations (RR 1.46 [95% CI: 0.80 – 2.58] P < .01).
Despite there being a heightened risk of suicide in this patient population, investigators observed that “nearly all patients diagnosed with concussion and/or mild TBI did not die by suicide.” They theorized that abnormal activity on functional magnetic resonance imaging (MRI) as well as abnormal structural connectivity in the brain regions necessary for cognitive and emotional processing—trends noted in recent meta-analyses of mild TBI neuroimaging studies—could explain this trend of depression in individuals exposed to more TBI.
“In addition, multiple neuropathological models have been proposed for how neurobehavioral impairment may occur in the short term and long term after concussion and/or mild TBI,” investigators noted.
The most notable of these—chronic traumatic encephalopathy (CTE)—has been associated with contact sports, concussions and/or mild TBI, and symptoms of depression, anxiety and impulsivity. That said, it’s also been reported in athletes without any history of concussion or mild TBI.
“The lack of a prior documented concussion and/or mild TBI might be because of underreporting of these conditions, but this also raises the possibility that subconcussive events could be sufficient to cause (CTE),” Fralick and colleagues explained.
Making reference to notable former National Football League (NFL) players Junior Seau and Mike Webster—both of whom had previously suffered from concussions in their playing days and subsequently died from suicide years after—as well as to the prevalence of concussions and/or TBI and suicide in military personnel, investigators stressed the significance of their assessment.
“Although there has been anecdotal evidence reported in newspaper reports, movies, and documentaries suggesting a link between concussion and/or mild TBI and subsequent suicide, past studies on the topic have been limited by small sample sizes and conflicting results,” investigators noted.
They also emphasized the high prevalence of both concussions, which occur approximately 4 million times in the US annually—with up to 25% of patients experiencing chronic neuropsychiatric symptoms including anxiety and depression for years after injury.
“Evaluating the potential association between concussion and/or mild TBI and suicide is important, because concussion and mild TBI are common, affect individuals of every age, and are often preventable,” Fralick and colleagues wrote. “Furthermore, even if the absolute risk of suicide is low, evidence of an association between concussion and mild TBI and suicide across a range of populations is important because of the seriousness of the outcome.”
In an essay accompanying the meta-analysis, Donald A. Redelmeier, MD, MSHR, and Junaid A. Bhatti, MBBS, MSc, PhD, of the Departments of Medicine and of Surgery at the University of Toronto, noted the accumulated findings do not prove causality over correlation.
“Patients who receive a diagnosis of a concussion might have already had a latent psychiatric illness that contributed to the incident and the outcome,” the pair argued. “For example, one shared factor could be alcohol use, which is often poorly identified in medical data. Disentangling such factors is difficult because it is unethical to randomize patients to receive a concussion.”
That said, they added that Fralick and colleagues’ greatest contribution is by creating a comprehensive review of medical science suggesting a significant association between TBI and subsequent suicide risk. Consequently, they advise clinicals use proper terminology and etiquette when diagnosing concussion-like symptoms, and neurologists should be keen to suicide risk and the additional factors involved in suicidality.
After all, they conclude, concussions can be lethal in their own way.
“The major implication of this meta-analysis is to highlight that an acute concussion might add to long-term neuropsychiatric illness,” Redelmeier and Bhatti prose. “Health care needs to focus on the prevention of concussions, although the cost-effectiveness of specific tactics that are based on engineering, education, equipment, or regulation is uncertain.”
The study, “Association of Concussion With the Risk of Suicide,” was published online in JAMA this week.