Objective To investigate the risk of traumatic brain injury (TBI) and post-injury mortality in patients with mental disorders.

Background Patients with mental disorders are at higher risk of injuries. However, the association between mental disorders and TBI is still not understood. We conducted case-control studies to investigate whether people with pre-existing mental disorders are at higher risk of TBI and post-injury mortality.

Methods Using reimbursement claims, we analysed 16 635 patients with TBI and 66 540 controls with adjustment of covariates to study the association of mental disorders and TBI. A nested case-control study was also conducted to analyse contributory factors for post-injury mortality.

Results People with mental disorders were at increased risk of TBI (odds ratio (OR) 1.94, 95% confidence interval (CI) 1.86 to 2.02). Men, older age, living in highly urbanised areas and patients on low income had a higher risk of TBI and post-injury mortality. Psychiatric medication intensity and frequency of psychiatric visits was significantly correlated with TBI in a severity dependent relationship (p for trend <0.0001). Patients receiving advanced psychiatric healthcare had an increased risk of TBI (OR 2.98, 95% CI 2.67 to 3.33) and post-injury mortality (OR 1.92, 95% CI 1.34 to 2.77). A history of receiving psychiatric related outpatient care (OR 1.77, 95% CI 1.70 to 1.85), hospitalisation (OR 3.21, 95% CI 2.79 to 3.70) or emergency visits (OR 3.53, 95% CI 3.15 to 3.94) were highly associated with subsequent TBI.

Conclusions Patients with mental disorders have an increased risk of TBI. Intensity of psychiatric medication is associated with increased post-injury mortality. Special attention to prevent TBI among this disabled population is mandatory.