Life-long criminals have smaller brains

Parents probably shouldn’t worry so much about their teenagers’ delinquent behaviour – provided they were well behaved in their earlier childhood.

This is according to a recent study which suggests that people who persistently lie, steal and bully have smaller brains and display aggressive behaviour from during their kindergarten years.

For the study which was led by University College London and published in The Lancet medical journal, brain scans of almost 700 people aged 45 were analysed – a third had a history of antisocial behaviour ranging from physical fighting to truancy.

The brain scans showed that people with a lifetime of convictions behind them had structurally smaller and thinner brains, some of which were in areas responsible for behaviour and emotion control.

The team also looked at their criminal records and questioned their teachers and nursery staff, identifying a group of 80 adults with a persistent history of antisocial behaviour and physical violence, ranging from biting other children in nursery to domestic violence as an adult.

In fact, researchers involved in the study were quick to insist that going off the rails as a teenager was fairly normal as participants who’d only caused trouble as adolescents didn’t have significant brain differences compared to the general population.

But they said far more attention should be paid to toddlers and young children who were persistently badly behaved and could be at risk of a life of antisocial behaviour, because of the way their brains were formed.

For the study, which was undertaken in New Zealand, the participants’ level of antisocial behaviour had been measured every two years from the age of seven to 26 using self-reporting and reports from parents, carers and teachers.

The participants were followed through adulthood, and 80 had what the researchers call ‘life-course-persistent’ antisocial behaviour. These people had on average been convicted five times between the age of 26 and 28.

The researchers took MRI brain scans of participants at the age of 45 and compared the cortical surface area and cortical thickness of 360 different regions of the cortex.

On average, across the entire brain, those who were antisocial into adulthood had a smaller surface area in 282 of 360 brain regions than people who had no history of antisocial behaviour, reports Medical Express.

They also had thinner cortex in 11 of 360 regions.

The areas effected have been previously linked to antisocial behaviour through their involvement in regulation of emotions, motivation and goal-driving behaviour.

“I think what we’ve seen with these data is they’re actually operating under some handicap at the level of the brain, so I think for me, this changes my conception of the ‘life course persistent’ antisocial individuals now, to thinking of someone who’s living life with some level of disability, and coping with that as part of their lifestyle,” says the study’s co-author Dr Terrie Moffitt.

The authors say the study provides the first robust evidence to suggest that underlying brain differences are linked to antisocial behaviour.

Study lead author Dr Christina Carlisi said those who commit crimes their whole life could benefit from more support throughout their lives.

“Our findings support the idea that, for the small proportion of individuals with life-course-persistent antisocial behaviour, there may be differences in their brain structure that make it difficult for them to develop social skills that prevent them from engaging in antisocial behaviour.”

However, the team cautions against brain imaging as a screening tool to identify people who may become life-long criminals.

The team acknowledged that it’s unclear if the structural brain differences were a cause of antisocial behaviour, or a result of a troubled life associated with crime.

“It’s unclear whether these brain differences are inherited and precede antisocial behaviour, or whether they’re the result of a lifetime of confounding risk factors (eg, substance abuse, low IQ, and mental health problems) and are therefore a consequence of a persistently antisocial lifestyle,” says co-author of the study Professor Essi Viding.