Neuroimaging reveals that teens are more likely to start smoking because they tend to have reduced gray matter in two key brain regions, suggesting they may play an important role in inhibition and addiction.

“Smoking is probably the most common addictive behavior in the world and the leading cause of death among adults,” says psychologist Trevor Robbins of the University of Cambridge. “The onset of the smoking habit most likely occurs during adolescence. Any way of determining the increased probability of this so that we can intervene in a targeted manner could help save millions of lives.”

An international team led by Fudan University bioinformatician Tianye Jia and cognitive neuroscientist Shiton Xiang compared brain MRI scans of more than 800 people collected at different time periods in the UK, Germany, France and Ireland. These volunteers also answered questionnaires about personality traits.

The researchers then compared those who started smoking at age 14 with those who did not smoke, and repeated with the same patients at age 19 and 23. The images showed that those who started smoking at age 14 had relatively less gray matter in the left ventromedial prefrontal cortex; the part of the brain involved in emotional regulation, decision making, and self-control.

A scan five years later showed that the opposite side of the same brain region (right) was also reduced in the smokers group compared to non-smokers. This side of the ventromedial prefrontal cortex has also been associated with pleasure.

“The ventromedial prefrontal cortex is a key region for dopamine, the brain’s pleasure chemical,” explains Cambridge psychiatrist Barbara Sahakian. “Dopamine has long been thought to affect self-control.”

The results of the surveys may suggest why.

“Both surveys examine the desire for immersive experience, but measure different behaviors,” explains Robbins. “The excitement seeking scale focuses on pleasant experiences, while the novelty seeking questionnaire contains items on impulsivity and rule breaking.”

Participants whose responses showed a greater propensity for sensation seeking were more likely to have reduced brain matter in the right ventromedial prefrontal cortex. Whereas, more novelty seeking was associated with less left gray matter. This leads to less inhibition and more risk-taking, behaviors that make adolescents more likely to smoke.

“Smokers then experience excessive gray matter loss in the right frontal lobe associated with substance-reinforcing behavior,” says Jia, pressing the thrill-seeking gratification button. “This may provide a causal explanation for how smoking begins in young people and how it becomes addictive.”

Another subgroup of the population studied was those who started smoking before the age of 19. They also had less gray matter in their left prefrontal cortex at age 14, but their right side was the same as non-smokers until they started smoking.

Thus, reduced substance in the left anterior lobe may be an inherited biomarker for people with a predisposition to addiction.

“Providing an alternative non-drug reward early in substance use may help prevent the transition to substance abuse,” Jia and colleagues say.

They want to know if their findings apply to vaping as well. One in five adult deaths in the United States is due to smoking. Understanding who is most at risk before they even begin can change their lives. Source