Levels of grey matter in two parts of the brain may be linked to a desire to start smoking during adolescence and the strengthening of nicotine addiction, a new study has revealed.
A team of scientists, led by the universities of Cambridge and Warwick in the UK and Fudan University in China, analysed brain imaging and behavioural data of over 800 young people at the ages of 14, 19 and 23.
They found that, on average, teenagers who started smoking by 14 years of age had markedly less grey matter in a section of the left frontal lobe linked to decision-making and rule-breaking.
Low grey matter volume in the left side of the ventromedial prefrontal cortex may be an “inheritable biomarker” for nicotine addiction.
In addition, the scientists found that the opposite, right part of the same brain region also had less grey matter in smokers.
Importantly, loss of grey matter in the right prefrontal cortex appears to speed up only after someone has started smoking. This region is linked to the seeking of sensations, according to the study that appeared in Nature Communications.
The team argued that less grey matter in the left forebrain could lower cognitive function and lead to “disinhibition” -- impulsive, rule-breaking behaviour arising from a limited ability to consider consequences. This may increase the chances of smoking at a young age.
“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,” said Professor Trevor Robbins, co-senior author from Cambridge’s Department of Psychology.
Annual deaths from cigarettes are expected to reach eight million worldwide by the end of the decade.
“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,” said Robbins.
Professor Barbara Sahakian from 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.”
The scientists also looked at the right ventromedial prefrontal cortex. Grey matter loss occurs in everyone as they age.
However, those who smoked from age 14 as well as those smoking from age 19 both ended up with excessive grey matter loss in the right frontal lobe.
Data at age 23 showed that grey matter volume in the right prefrontal cortex shrank at a faster pace in those who continued to smoke, suggesting an influence of smoking itself on prefrontal function, the findings showed.