Young  people who are heavy smokers have clear differences in their brains compared to lighter smokers, according to a recent study published in the journal Neuropsychopharmacology. 

"Earlier studies of older participants showed that the smokers had structural differences in various brain regions," senior author Edythe D. London, from the Semel Institute for Neuroscience and Human Behavior at UCLA and the David Geffen School of Medicine in Los Angeles, told Reuters.

Studies of adolescent animals also showed that nicotine damaged and killed brain cells, added London. 

"While the results do not prove causation, they suggest that there are effects of cigarette exposure on brain structure in young smokers, with a relatively short smoking history," London said.

For the study, researchers mapped the brains of 42 people ages 16 to 21 using magnetic resonance imaging (MRI) and asked them about their smoking history and cravings.

Eighteen of the participants were smokers who smoked six to seven cigarettes per day.

Researchers found no clear differences in the brains of smokers versus non-smokers.

However, the did see a difference among smokers.

Based on their findings, those who reported smoking more cigarettes tended to have a thinner insula, a region of the cerebral cortex involved in decision making, the effects seemed confined to the right insula.

"Previous studies have suggested the insula plays a central role in tobacco dependence, with the highest density of nicotine receptors in the brain,. Reuters reported.

Investigators also found that people with a thinner insula had more cravings and felt more dependent on cigarettes. 

"Because the brain is still undergoing development, smoking during this critical period may produce neurobiological changes that promote tobacco dependence later in life," London said.

She added that changing the structure of the insula may affect future smoking dependence and other substance abuse.

"It is possible that changes in the brain from prolonged exposure help maintain dependence," she said.

According to London, people who start smoking early in life tend to have more trouble quitting and have more serious health consequences than those who start later.

However, since the study only assessed smokers at one point in time, it doesn't prove a causal relationship between cigarettes and brain changes.

"It is possible that such changes pre-dated the smoking, i.e. they were not caused by smoking," Dr. Nasir H. Naqvi,  a substance abuse researcher at Columbia University in New York who was not involved in the study, told Reuters. "The only way to know this is to take a group of adolescents who have never smoked, follow them over time, and then see who starts smoking, and then compare them to the adolescents who never started smoking."