Teens' desire to start smoking, and later to keep smoking, may be linked to differences in gray matter in their brains, a new study reveals.
Researchers found that reduced gray matter in the left frontal lobe was found in kids who started smoking by age 14. This area is involved in decision-making and rule-breaking.
Once they started smoking, they also had reduced gray matter in the right frontal lobe, a region associated with seeking pleasure.
"Smoking is perhaps the most common addictive behavior in the world, and a leading cause of adult mortality,"said co-senior author Trevor Robbins, a professor in the Department of Psychology at the U.K.'s Cambridge University. "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."
Gray matter is brain tissue that processes information and contains all of the brain's neurons. Growth of gray matter peaks before adolescence.
The evidence that these teens had low gray matter volume in the left side of the prefrontal cortex may be an "inheritable biomarker"for nicotine addiction, the study authors suggested.
The loss of gray matter in the right prefrontal cortex appeared to speed up only after someone started smoking.
"In our study, reduced gray matter in the left prefrontal cortex is associated with increased rule-breaking behavior, as well as early smoking experiences. It could be that this rule-breaking leads to the violation of anti-smoking norms,"Robbins said in a university news release.
Having less gray matter in the left forebrain could lead to a lack of inhibition, the authors said, with impulsive, rule-breaking behavior arising from a limited ability to consider the consequences.
The shrinking gray matter on the right side may then weaken control over smoking. Excessive loss of gray matter in the right brain was also linked to binge drinking and marijuana use, researchers said.
Together, these findings suggest a damaged "neurobehavioral mechanism"that can lead to early nicotine use and long-term addiction.
"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,"study co-author Barbara Sahakian, from Cambridge's Department of Psychiatry, said in the release.
The research team analyzed brain scans and behavioral data from more than 800 young people at the ages of 14, 19 and 23 using information from the IMAGEN project at sites in the United Kingdom, Germany, France and Ireland.
They compared brain scans for those who had smoked by age 14 with those who had not. They repeated this for the same participants at ages 19 and 23.
Those who started smoking by age 14 and by age 19 had less gray matter in their left prefrontal cortex at 14, suggesting a potential causal influence.
The 19-year-old smokers who did not start during adolescence had similar gray matter levels in the right brain at age 14 to those who never smoked at all, which suggests a rapid reduction after beginning smoking.
Looking at the data from the participants at age 23, the researchers saw that gray matter volume in the right prefrontal cortex shrank at a faster pace in those who continued to smoke.
Researchers used the questionnaires to examine personality traits.
The findings were published Aug. 15 in the journal Nature Communications.
"Less gray matter in the left frontal lobes is linked to behaviors that increase the likelihood of smoking in adolescence,"said lead author Tianye Jia, from Fudan University in China. "Smokers then experience excessive loss of gray matter in the right frontal lobes, which is linked to behaviors that reinforce substance use. This may provide a causal account of how smoking is initiated in young people, and how it turns into dependence."
More information
The U.S. Centers for Disease Control and Prevention has more on youth tobacco use.
SOURCE: University of Cambridge, news release, Aug. 15, 2023
