The Risk of Suicide Attempts After Head Injury: A Matched UK Population-Based Cohort Study

Traumatic brain injuries are associated with an increased risk of suicide; the risk of suicide after other head injuries, particularly in the general population, remains unclear. We aimed to determine whether people with head injuries are at higher risk of suicide compared with people without head injuries.

A 20-year population-based matched cohort study was conducted using nationally representative electronic primary health care records linked to Hospital Episode Statistics and Office for National Statistics data. Adults (≥18 years) with a head injury were matched 1:4 with individuals without a head injury by age, sex, and geographical location. Individuals without data linkage or with a history of self-harm or suicide attempt before the head injury were excluded. The primary outcome was risk of suicide attempt (including death by suicide). Secondary outcomes were risk factors of suicide attempt and risk of death by suicide. Subgroup analysis was conducted to investigate risk of suicide attempt by age group, sex, social deprivation level, ethnicity, and history of mental health conditions. Adjusted hazard ratios (HRs) were calculated using Cox proportional hazards regression.

The mean age of people with and without head injuries was 52.4 years (SD 22.7), and 51% were female. Of 389,523 people with head injuries, 5,107 suicide attempts were recorded (incidence rate 2.4 per 1,000 person-years) compared with 9,815 among 1,489,675 adults without head injuries (incidence rate 1.6 per 1,000 person-years), resulting in an adjusted HR of 1.21 (95% CI 1.17-1.25). Risk factors of suicide attempt were first 12 months after head injury, higher deprivation, and a history of a mental health condition. The adjusted HR for death by suicide was 0.74 (95% CI 0.66-0.84); this became nonsignificant after controlling for competing risk of death (sub-HR 0.91, 95% CI 0.81-1.03). Risk of suicide attempt was higher in all subgroups investigated, including those without any baseline mental health condition.

These findings have implications for clinical practice and health policy. The development and testing of suicide risk assessment and prevention strategies for people with head injuries should be investigated, especially within the first 12 months after head injury and irrespective of mental health history.