BY LIZETTE BORRELI
People who experienced a traumatic brain injury (TBI) had an increased risk of suicide, compared to the general population without TBI, according to a nationwide retrospective cohort study in Denmark published on August 14 in the Journal of the American Medical Association.
Among those with TBI, the absolute suicide rate was almost twice as high compared with those who did not have TBI: 41 per 100 000 person-years (95% CI, 39.2-41.9) compared to 21 per 100 000 person-years (95% CI, 19.7-20.1), respectively.
Prior studies have measured the link between TBI and risk of suicide, but the sample sizes were small and they had limited data. In a 2014 Swedish study published in JAMA Psychiatry, researchers found a three-fold higher risk of suicide in patients with TBI, compared to the age- and sex-matched general population, but the study did not account for risk factors like preexisting psychiatric illness and nonfatal deliberate self-harm.
In an effort to examine the association between TBI and subsequent suicide, a team of international researchers used patient nationwide registers covering about 7.4 million people, aged 10 years or older, living in Denmark from 1980 to 2014. TBI was recorded in the National Patient Register, which covers three forms of medical contacts, including mild TBI; skull fracture without documented TBI, and severe TBI. The team assessed the link between TBI and suicide, factoring in the number of medical contacts for likely distinct TBI events, accumulated number of days in hospital treatment for TBI, and time since last medical contact for TBI.
They also considered pre-existing psychiatric illness. Individuals who were diagnosed with a psychological illness after their TBI had a higher risk of suicide (IRR, 4.90; 95% CI, 4.55-5.29; p< .001) than did those with TBI only, as were those who had engaged in deliberate self-harm after experiencing their TBI (IRR, 7.54; 95% CI, 6.91-8.22; p<.001).
A cross-analysis with the Danish Cause of Death registry revealed that over the span of 35 years, 10.2 percent of the 34,529 deaths by suicide had prior medical contact for TBI: 7.8 percent with mild TBI, 0.5 percent with skull fracture without documented TBI, and 1.9 percent with severe TBI.
Compared with the general population, the researchers found the risk of suicide after TBI was elevated (p<.001) with an incident rate ratio (IRR) of 3.67 (95% CI, 3.33-4.04) within the first six months, and an IRR of 1.76 (95% CI, 1.67-1.86) after seven years. The risk was higher among patients who experienced their first medical contact for TBI between the ages of 16 and 20 (IRR, 3.01; 95% CI, 2.74-3.30). Those diagnosed with psychological illness after TBI were also at an increased risk for suicide (IRR, 4.90; 95% CI, 4.55-5.29; p<.001).
Overall, TBI severity conferred a higher risk of suicide: mild TBI was associated with an IRR of 1.81 (95% CI, 1.74-1.88); skull fractures without documented TBI had an IRR of 2.01 (95% CI, 1.73-2.34, p< .001); and severe TBI was associated with an IRR of 2.38 (95% CI, 2.20-2.58, p< .001), compared to those without TBI.
"Traumatic brain injury is a major public health problem that has many serious consequences, including suicide," wrote the researchers, led by Trine Madsen, PhD, of the Danish Research Institute of Suicide Prevention, Mental Health Centre Copenhagen, Capital Region of Denmark. But they said that the risk could be ameliorated by emphasizing strategies that prevent TBI, for example, encouraging the use of helmets to deter possible TBI from falls from bicycle accidents.
Study limitations included a lack of data on mild TBIs prior to 1995; no information regarding what specific treatment TBI patients' received; the inability to verify whether medical visits were clinic checkups, emergency room visits, or hospital stays. In addition, they were unable to retrieve data from people who didn't seek medical attention after a mild TBI, or for mild psychiatric disorders, or for deliberate self-harm.
The Mental Health Services Capital Region Denmark and the Lundbeck Foundation funded the study.
The researchers report no conflicts of interest.
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Madsen T, Erlangsen A, Orlovska S, et al. Association between traumatic brain injury and risk of suicide. JAMA 2018; Epub 2018 Aug 14.