Could a traumatic brain injury (TBI) lead to criminal behavior? A modest increase in the risk of offending, including violent offending, follows a hospital-documented TBI, an Australian research group finds.

“Successful reduction in the prevalence of TBI… could also have benefits in terms of crime rate reduction,” wrote the authors in the conclusion of their new study.

Traumatic brain injury occurs when the head suddenly and violently hits an object or when an object pierces the skull. Symptoms, though wide-ranging, may include confusion, an immediate loss of consciousness (for a few seconds or minutes), headache, blurred vision or tired eyes, dizziness, ringing in the ears, lightheadedness, mood changes, bad taste in the mouth, fatigue, a change in sleep patterns, and trouble with memory, concentration, attention, or thinking.

Past studies consistently show higher-than-average rates of traumatic brain injury among criminal offenders. Based on such findings, some neuroscientists have suggested “many offences may be a consequence of TBI-related behavioral dysregulation,” the authors of the current study noted in their introduction. Can such speculation be proven?

Trauma and Consequence

To investigate, the team collected and analyzed administrative data collected by the Western Australia Departments of Health and Corrective Services and the Western Australia Drug and Alcohol Office. First, the researchers identified people born between 1980 and 1985 whose hospital records included a TBI. For each person identified, the researchers then matched and compared them to three randomly-selected people of the same sex and birth year as well as one same-sex full-sibling (if available). None of these many “controls” had a record of TBI.

Of the total 136,100 individuals born in Western Australia between 1980 and 1985, the team included in their study a total of 7,694 people who sustained a TBI: 5,018 males and 2,676 females. The average age at first TBI was 10.6 years old for the boys and 6.9 years old for the girls.

Relative to their community controls, past TBI sufferers had two times the rate of both criminal convictions and mental illness. The rate of conviction was nearly 18 percent among males with a record of TBI versus 10 percent among males without, the researchers discovered; among females, nine percent versus four percent.

“The results from the current study would be consistent with a causal relationship between TBI and subsequent criminal convictions, and convictions for violence in particular, in both sexes,” noted the authors in their conclusion.

Rates of mental illness ranged as high as 19 percent for males with a history of TBI versus just nine percent for males without, while 22 percent of TBI females had a diagnosis of mental illness compared to just 13 percent of females without TBI.

Going forward, the researchers suggest future studies attempt predictive models to better explain the complex relationship between TBI and criminality, with a focus on gender and ethnic differences, maternal and birth characteristics, and age at time of the brain injury.

Source: Schofield PW, Malacova E, Preen DB, et al.  Does Traumatic Brain Injury Lead to Criminality? A Whole-Population Retrospective Cohort Study Using Linked Data. PLOS ONE. 2015.