A new study from University of California, Los Angeles shows that smoking is associated with structural changes in the brains of teenagers.

Research has shown that adolescents' brains undergo pruning to create new, stronger neural networks. Physical changes to brain during this critical period might lead to long-term problems.

What's worse is that these changes can occur even if the duration of smoking history was relatively short.

"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," Edythe London, a professor of psychiatry and of molecular and medical pharmacology at UCLA and a senior author of the study, told Reuters.

The study was based brain scans of 42 participants between ages 16 and 21 years.  Smoking history and cravings for cigarettes of each participant were also assessed by the researchers. In this study, 24 participants were non-smokers while 18 were smokers.

Researchers specifically looked at a part of the brain called as the insula, which is known to help humans regulate emotions and make decisions.

Insula - a prune-sized region in the brain - made headlines in 2007 when another team of researchers had found that damage to this region helps people give up smoking.

Previous research has shown that the insula has the highest number of nicotinic acetylcholine receptors, making it a hub for tobacco dependence.

London and team measured the cortical thickness of the insula and found that it was associated with smoking history of the person.

"Our results suggest that participants with greater smoking exposure had more severe nicotine dependence, more cigarette craving and less insular thickness than those with less exposure," London said in a news release.

"While this was a small study and needs to be replicated, our findings show an apparent effect of smoking on brain structure in young people, even with a relatively short smoking history. And that is a concern. It suggests that smoking during this critical time period produces neurobiological changes that may cause a dependence on tobacco in adulthood," London said.

According to data from the US Centers for Disease Control and Prevention, some 6.7 percent of middle school and 23.3 percent of high school students currently smoke tobacco-containing products such as cigarettes and hookah.

The study is published in the journal Neuropsychopharmacology.