Association Between Traumatic Brain Injury and Risk of Suicide

Abstract

Importance: Traumatic brain injuries (TBIs) can have serious long-term consequences, including psychiatric disorders. However, few studies have assessed the association between TBI and risk of suicide.

Objective: To examine the association between TBI and subsequent suicide.

Design, setting, and participants: Retrospective cohort study using nationwide registers covering 7 418 391 individuals (≥10 years) living in Denmark (1980-2014) with 164 265 624 person-years' follow-up; 567 823 (7.6%) had a medical contact for TBI. Data were analyzed using Poisson regression adjusted for relevant covariates, including fractures not involving the skull, psychiatric diagnoses, and deliberate self-harm.

Exposure: Medical contacts for TBI recorded in the National Patient Register (1977-2014) as mild TBI (concussion), skull fracture without documented TBI, and severe TBI (head injuries with evidence of structural brain injury).

Main outcomes and measures: Suicide recorded in the Danish Cause of Death register until December 31, 2014.

Results: Of 34 529 individuals who died by suicide (mean age, 52 years [SD, 18 years]; 32.7% women; absolute rate 21 per 100 000 person-years [95% CI, 20.8-21.2]), 3536 (10.2%) had medical contact: 2701 with mild TBI, 174 with skull fracture without documented TBI, and 661 with severe TBI. The absolute suicide rate was 41 per 100 000 person-years (95% CI, 39.2-41.9) among those with TBI vs 20 per 100 000 person-years (95% CI, 19.7-20.1) among those with no diagnosis of TBI. The adjusted incidence rate ratio (IRR) was 1.90 (95% CI, 1.83-1.97). Compared with those without TBI, severe TBI (absolute rate, 50.8 per 100 000 person-years; 95% CI, 46.9-54.6) was associated with an IRR of 2.38 (95% CI, 2.20-2.58), whereas mild TBI (absolute rate, 38.6 per 100 000 person-years; 95% CI, 37.1-40.0), and skull fracture without documented TBI (absolute rate, 42.4 per 100 000 person-years; 95% CI, 36.1-48.7) had an IRR of 1.81 (95% CI, 1.74-1.88) and an IRR of 2.01 (95% CI, 1.73-2.34), respectively. Suicide risk was associated with number of medical contacts for TBI compared with those with no TBI contacts: 1 TBI contact, absolute rate, 34.3 per 100 000 person-years (95% CI, 33.0-35.7; IRR, 1.75; 95% CI, 1.68-1.83); 2 TBI contacts, absolute rate, 59.8 per 100 000 person-years (95% CI, 55.1-64.6; IRR, 2.31; 95% CI, 2.13-2.51); and 3 or more TBI contacts, absolute rate, 90.6 per 100 000 person-years (95% CI, 82.3-98.9; IRR, 2.59; 95% CI, 2.35-2.85; all P < .001 for the IRR's). Compared with the general population, temporal proximity since the last medical contact for TBI was associated with risk of suicide (P<.001), with an IRR of 3.67 (95% CI, 3.33-4.04) within the first 6 months and an incidence IRR of 1.76 (95% CI, 1.67-1.86) after 7 years.

Conclusions and relevance: In this nationwide registry-based retrospective cohort study individuals with medical contact for TBI, compared with the general population without TBI, had increased suicide risk.

Figure.. Incidence of Suicide Among Denmark Residents After Traumatic Brain Injury (TBI), 1980-2014^a

^aSee eTable 2 for complete data estimates. Error bars indicate 95% CIs. ^bAdjusted for sex, age, and calendar period, educational level, cohabitation status, marital status, socioeconomic status, fractures not involving the skull or the spine, epilepsy, Charlson comorbidity index, and psychiatric illness prior to traumatic brain injury (TBI) and prior to TBI-deliberate self-harm. Less than 1 day indicates same-day discharge. ^cAdjusted for all characteristics listed in footnote b except fractures not involving the skull or the spine.