Brain injury linked to criminal behaviour in new study

Damage to a specific brain pathway may contribute to criminal or violent behaviour in some people after brain injury, a new study has found.

The research analysed brain scans from 17 individuals who began committing crimes following injuries caused by strokes, tumours or traumatic brain injury.

These were compared with scans from 706 people who had other neurological symptoms, such as memory loss or depression.

Researchers found that damage to the right uncinate fasciculus—a white matter tract that connects brain regions involved in emotion and decision-making—was the most consistently affected area in those who developed criminal behaviour.

The same pattern was observed in people who committed violent offences.

The study was led by researchers at the University of Colorado Anschutz Medical Campus, Brigham and Women’s Hospital and Harvard Medical School.

Christopher M. Filley is professor emeritus of neurology at the University of Colorado School of Medicine.

He said: “This part of the brain, the uncinate fasciculus, is a white matter pathway that serves as a cable connecting regions that govern emotion and decision-making.

“When that connection is disrupted on the right side, a person’s ability to regulate emotions and make moral choices may be severely impaired.”

Although brain injuries are known to cause memory loss or motor difficulties, the role of neurological damage in guiding social behaviours like criminality is more contested.

Isaiah Kletenik is assistant professor of neurology at Harvard Medical School and lead author of the study.

Kletenik said: “While it is widely accepted that brain injury can lead to problems with memory or motor function, the role of the brain in guiding social behaviours like criminality is more controversial.

“It raises complex questions about culpability and free will.”

Kletenik said his interest in the issue began during his behavioural neurology training at the University of Colorado School of Medicine, where he treated patients who developed violent behaviour after brain tumours or degenerative conditions.

He said: “These clinical cases prompted my curiosity into the brain basis of moral decision-making and led me to learn new network-based neuroimaging techniques at the Center for Brain Circuit Therapeutics at Brigham and Women’s Hospital and Harvard Medical School.”

To strengthen the findings, the team conducted a full connectome analysis—a detailed map of how brain regions are interconnected—which confirmed that damage to the right uncinate fasciculus was most strongly associated with the onset of criminal behaviour.

Filley said: “It wasn’t just any brain damage, it was damage in the location of this pathway. Our finding suggests that this specific connection may play a unique role in regulating behaviour.”

The uncinate fasciculus links areas of the brain that support reward-based decision-making with those involved in processing emotion.

When this connection is disrupted—particularly on the right side—people may experience difficulty with impulse control, anticipating consequences or feeling empathy.

The researchers stressed that not everyone with this type of brain damage becomes violent, but it may play a role in some cases of newly emerging criminal behaviour after injury.

Filley said: “This work could have real-world implications for both medicine and the law. Doctors may be able to better identify at-risk patients and offer effective early interventions.

“And courts might need to consider brain damage when evaluating criminal responsibility,”

The findings also raise complex ethical and legal questions.

Kletenik said: “Should brain injury factor into how we judge criminal behaviour?

“Causality in science is not defined in the same way as culpability in the eyes of the law.

“Still, our findings provide useful data that can help inform this discussion and contributes to our growing knowledge about how social behaviour is mediated by the brain.”