Study shows why some teens can't help acting on impulse

AN IRISH-LED international research effort has tracked down networks in the brain that cause some young teens to behave more impulsively than others.

It helps to explain why some rush to participate in risky activities, such as drinking and drug-taking, while others don’t.

Other impulse-related brain networks identified by the team were associated with the symptoms of attention-deficit hyperactivity disorder, or ADHD.

Impulsive behaviour in young teens is a source of worry for most parents, but some teens seem particularly inclined to take risks and experiment with drink, drugs and tobacco, according to Prof Hugh Garavan.

He and fellow Irish researcher Dr Robert Whelan were the lead authors of this major study, carried out in eight centres in Ireland, Britain, Germany and France.

Prof Garavan and Dr Whelan are now based in the department of psychiatry and psychology at the University of Vermont in the US.

The research project began five years ago, however, at the Trinity College Institute of Neuroscience, Prof Garavan said.

The study was based on the use of brain scanning and a detailed cognitive assessment of 14-year-old subjects. The goal was to better understand what causes impulsive behaviour.

Funded by the EU, the researchers carried out the largest imaging study of the human brain ever conducted, including 250 brain scans in Dublin. Most brain scan studies involve no more than 10 or 15 subjects, but this study had so far carried out 2,400 scans, Prof Garavan said.

Important new findings have come out of the research, which is published this morning in the journal Nature Neuroscience.

It took about 10 hours to scan each of the subjects and do the cognitive assessments. Together these allowed the researchers to link risk-taking, impulsive behaviours with specific parts of the brain.

They discovered seven networks associated with risk-taking. Some of them increased the likelihood of this behaviour and others were meant to inhibit it but failed to do so, Prof Garavan said.

One network, if overactive, was directly associated with risk-taking using alcohol. Another inclined the subject to more general abuse of drink, drugs or tobacco, but only if its activity was reduced.

“Testing for lower function in this and other brain networks could, perhaps, be used by researchers some day as a risk factor or biomarker for potential drug use,” Prof Garavan said.