The vast majority of young males detained in Scotland's youth offender institutes have a medical history of serious head injuries, according to new research.

The study by Glasgow University found that 80% of inmates had suffered significant head trauma in the past, with many exposed to repeated head injuries over time.

The findings build on previous research showing clear behavioural effects associated with brain trauma such as impatience, intolerance, impulsivity, and irritability, which in turn impair an individual's ability to control aggressive, violent, and antisocial impulses.

READ MORE: Violent crime higher in siblings with a history of head injuries 

A 2011 analysis based on Sweden's population found that the risk of committing violent crimes such as murder, robbery, arson, or sexual attacks was more than three times higher among people with a history of traumatic brain injuries compared to people of the same age and sex without head trauma, even after adjusting for factors such as substance abuse and deprivation.

The Herald:

When siblings with and without head injuries were compared, the risk of committing violent offences remained twice as high for those with a traumatic brain injury.

The Glasgow University study recruited juvenile males from HM Young Offenders Institution (YOI) Polmont, Scotland’s national holding facility for young people aged between 16-21 years of age.

A total of 103 out of the 305 young men held at the facility took part in the research. 

Overall, a history of significant head injury was found in 82 of the young men (80%), while 69 of that group – two thirds of the study participants overall – had experienced repeated head injuries over long periods of time.

The causes of significant head injuries in young male offenders tended to be fighting and assault.

Researchers found no evidence for differences in cognitive test performance or offending in juveniles with and without a history of signficant head injury.

However, there was evidence to suggest that the young offenders affected by significant head injury did have poorer behaviour control, and were more often reported for incidents in prison than those without.

READ MORE: Call to screen criminals for brain injuries to reduce re-offending

Furthermore, while poor mental health and problems associated with substance use were common among young male offenders as a whole, those with a history of serious head injury were significantly more likely to experience mental health problems such as anxiety and distress.

Researchers believe these signs – of poorer behavioural control alongside greater psychological distress – suggest that young males with significant head injury may be at greater risk of re-offending and becoming lifelong offenders.

The study's lead author, Professor Tom McMillan, said: “Our study reveals important new information on both the prevalence and the impacts of significant head injury in young male offenders in Scotland.

"Until now a limited understanding of this area has made it difficult for prisons to develop effective management and intervention strategies to help improve these young people’s health and reduce the chances of reoffending.

“The study findings suggest that there is a need for juvenile prisoner programmes to take into account the impacts of significant head injuries, and also a need for more work to be done to reduce future head injury risks in this group.

"This is likely to require training and education of staff and education of prisoners about head injury.”

The Herald:

READ MORE: Three concussions associated with worsening brain function

Disability associated with significant head injury was less common, at 13%, in young male offenders than in adult male or female offenders.

However, the prevalence of significant head injury was equally as high in each of these groups.

Previous research has shown that the risk of a future head injury is high in those who already have a history of these injuries, and that significant head injuries associated with disability are more common in older males.

As a result, the authors warn that young male offenders may be at greater risk of future disability than previously thought.

The study, which was funded by the Scottish Government, is published in the journal PLOS ONE.