Single concussion linked to violence

04 May, 2023

New AUT research shows even a mild traumatic brain injury (TBI) like concussion significantly increases the risk of criminal behaviour over the following decade.

The findings, published this week in Frontiers in Psychiatry, indicate those who experience a mild TBI have more criminal convictions and court charges for violent offences following their injury than those who don’t.

The risk of criminal behaviour is higher amongst men and further increases if people have had more than one brain injury, says Dr Alice Theadom, Professor of Clinical Sciences at AUT and one of the paper’s authors. However, there is no evidence that other crimes, such as fraud, drug, or traffic offences, increase.

“Other studies have shown severe brain injuries in childhood and adolescence are linked to criminal behaviour,” says Professor Theadom. “But our study reveals a specific link between milder TBIs, such as concussion, and how it can influence behaviour across a person’s lifetime.”

One possible explanation for the link is the cognitive and emotional difficulties that can arise from mild TBIs, Professor Theadom says. These include difficulty in processing information, making decisions quickly, and irritability, all of which can increase the risk of a violent response to a situation.

However, Professor Theadom says the relationship between mild TBIs and violent offences is still "very complex”.

“It is likely a mild TBI exacerbates other risk factors such as mental health difficulties, drug and alcohol, and social deprivation by reducing people’s ability to cope, make good decisions, and manage emotional reactions to events.”

Those impulse actions are more likely to result in violent offences than other criminal behaviour, Professor Theadom says.

The study used administrative data from Stats NZ’s Integrated Data Infrastructure (IDI). In particular, the authors drew from health and justice records to compare criminality in those who had suffered a mild TBI compared to those who had orthopaedic injuries such as broken legs.

Co-author Professor Gail Pacheco, Director of AUT’s New Zealand Work Research Institute (NZWRI), says the use of linked population-wide data allowed the researchers to construct a comparative group based on various socio-economic dimensions, including past criminal history.

Professor Pacheco says this ensures the characteristics of those who experience TBI are not driving the results.

“The potential cost of TBIs is huge. This study also highlights the importance of indirect effects, such as those that spillover into wellbeing domains beyond physical health. It’s clear that identifying and treating such injuries is important,” Professor Pacheco says.

While there has been increased awareness of the risks of TBI in professional sports, this research highlights its impact on a wider range of people.

“We are all at risk of sustaining a mild TBI whether it’s from a traffic accident, falling over in the street, hitting our head on a kitchen cupboard, playing a sport, or being assaulted,” Professor Theadom says.

The new research is just the start of a long-term process of investigation into the impact of TBIs on sufferers.

“We are now working on a series of projects looking at how we screen for brain injuries and improve access to treatment for those who need it,” says Professor Theadom.

How to spot a brain injury

Look out for signs including:

A glazed look
Difficulty getting up
Poor coordination
Sensitivity to light or noise
Repeating questions or statements
Head or neckache

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