Neuroimaging reveals that adolescents are more inclined to start smoking when gray matter is lost in two important areas of their brains. This suggests that it may play a significant role in inhibition and addiction. Trevor Robbins, a psychologist at the University of Cambridge, states: "Smoking may be the most common addictive behavior worldwide and the leading cause of adult mortality. The habit of smoking is likely to begin during adolescence. Any method to uncover an increased likelihood of this, so we can target interventions, could help save millions of lives."
An international team led by bioinformatics scientist Tianyi Jia from Fudan University and cognitive neuroscientist Chitong Xiang compared MRI scans of over 800 individuals, collected from the UK, Germany, France, and Ireland at different time points. These volunteers also answered questionnaires regarding their personality traits. The researchers compared those who began smoking at 14 years old with non-smokers, repeating this with the same subjects at ages 19 and 23.
Images revealed that those who started smoking at age 14 had relatively less gray matter in the left ventral prefrontal cortex—an area of the brain involved in emotional regulation, decision-making, and self-control. Scans conducted five years later indicated that the corresponding part of the same brain area (on the right) had also decreased in the smokers compared to non-smokers. This side of the ventral prefrontal cortex is also linked to pleasure.
Barbara Sahakian, a psychologist at Cambridge, explains that "the ventral prefrontal cortex is a key region for dopamine, the pleasure-causing chemical in the brain. In addition to its role in rewarding experiences, dopamine is long believed to affect self-control." The study also included another subset of participants who started smoking at age 19. They also had less gray matter in the left prefrontal cortex at age 14, but the right side was similar to non-smokers even after starting to smoke. Thus, the decrease in matter in the left prefrontal cortex may be a heritable biological marker in individuals predisposed to addiction.
