Brains of under-age smokers may be different to their peers, say University of Cambridge scientists and colleagues

Under-age smokers may have different brains than their teenage peers who do not smoke, a new study suggests.

The findings indicate that levels of grey matter – the brain tissue that processes information – in two parts of the brain may be linked to a desire to start smoking during adolescence and the strengthening of nicotine addiction.

Researchers say that any way of identifying who is more likely to develop a smoking habit could help save millions of lives.

A team of scientists, led by the University of Cambridge and the University of Warwick and Fudan University in China, analysed brain imaging and behavioural data of more than 800 young people at the ages of 14, 19 and 23.

On average, teenagers who started smoking by the time they were 14 had markedly less grey matter in a section of the left frontal lobe linked to decision-making and rule-breaking.

Prof Trevor Robbins, co-senior author from the University of Cambridge’s Department of Psychology, said: “Smoking is perhaps the most common addictive behaviour in the world, and a leading cause of adult mortality. The initiation of a smoking habit is most likely to occur during adolescence Any way of detecting an increased chance of this, so we can target interventions, could help save millions of lives.”

He added: “In our study, reduced grey matter in the left prefrontal cortex is associated with increased rule-breaking behaviour, as well as early smoking experiences. It could be that this rule-breaking leads to the violation of anti-smoking norms.”

While brain development continues into adulthood, grey matter growth peaks before adolescence.

According to the researchers, low grey matter volume in a particular area at the front left side of the brain may be an inherited biomarker (molecule) for nicotine addiction. This could have implications for prevention and treatment.

The scientists also found that the opposite, right part of the same brain region also had less grey matter in smokers.

According to the study, once a nicotine habit takes hold, grey matter in the right frontal lobe shrinks, which may weaken control over smoking by affecting the way pleasure is sought and managed.

Co-author Professor Barbara Sahakian from the University of Cambridge’s Department of Psychiatry said: “The ventromedial prefrontal cortex is a key region for dopamine, the brain’s pleasure chemical. As well as a role in rewarding experiences, dopamine has long been believed to affect self-control.

“Less grey matter across this brain region may limit cognitive function, leading to lower self-control and a propensity for risky behaviour, such as smoking.”

Lead author Prof Tianye Jia, from Fudan University, added: “Less grey matter in the left frontal lobes is linked to behaviours that increase the likelihood of smoking in adolescence.

“Smokers then experience excessive loss of grey matter in the right frontal lobes, which is linked to behaviours that reinforce substance use. This may provide a causal account of how smoking is initiated in young people, and how it turns into dependence.”