Does Traumatic Brain Injury Lead to Criminality? A Whole-Population Retrospective Cohort Study Using Linked Data

Abstract

Background: Traumatic brain injury (TBI) may be a risk factor for criminal behaviour however multiple factors potentially confound the association.

Methods: Record linkage and Cox proportional hazards regression analyses were used to examine the association between hospital-recorded TBI (n = 7,694) and subsequent first criminal conviction in a retrospective cohort matched 1:3 with 22,905 unaffected community controls and full-sibling controls (n = 2,397). Aboriginality, substance abuse, social disadvantage, and mental illness were included in analyses as potential confounders.

Results: In multivariable models, relative to general population controls, TBI was associated with any conviction (males: Hazard Ratio (HR) = 1.58 (95% CI 1.46 to 1.72); females: HR = 1.52 (95% CI 1.28 to 1.81)); and similar Hazard Ratios were obtained for the sibling analyses in males (HR = 1.68 (95% CI 1.31-2.18)) and females (HR 1.27 (95% CI 0.71-2.29)). TBI was also associated with violent convictions relative to the general population, (males: HR = 1.65 (95% CI 1.42 to 1.92); females HR = 1.73 (95% CI 1.21 to 2.47)), and in analyses with sibling controls in men (HR = 1.89 (95% CI 1.20-3.00)), but not in women (HR 0.73, 95% CI 0.29-1.81)).

Conclusion: The results support a modest causal link between TBI and criminality after comprehensive adjustment for confounding. Reducing the rate of TBI, a major public health imperative, might have benefits in terms of crime reduction.

Fig 1. Overview of Sampling.

Flowchart depicts the participant numbers that were included and excluded. *10 years is considered the age of criminal responsibility in Australia.

Fig 2. Forest Plot of Unadjusted and Adjusted Hazard Ratios for Any and Violent Convictions.

Figure depicting the associations between TBI and any violent offending, relative to the non- exposed comparison groups: general community, full siblings, or twins.