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Teen, young adult smoking may alter brain structure

A new UCLA study has reported that cigarette smoking may cause physical changes in brains of young smokers
A new UCLA study has reported that cigarette smoking may cause physical changes in brains of young smokers
Robin Wulffson, M.D.

A new UCLA study has reported that cigarette smoking may cause physical changes in brains of young smokers. The findings were published online on March 3 in the journal Neuropsychopharmacology.

The study authors noted that, sadly, teens and young adults smoke more than any other age group in the United States. They explain that the period of life ranging from late adolescence to early adulthood is also the period during which the brain is still developing. Their new study suggests that teen and young adult smokers may experience changes in the structures of their brains due to cigarette smoking, nicotine dependence, and craving. In addition, these worrisome changes can occur in individuals who have been smoking for relatively short period of time. Another disturbing finding from the study suggests that neurobiological changes, which may result from smoking during this critical period, could explain why adults who began smoking at a young age have extreme difficulty in quitting when they are older.

“Although we are not certain whether the findings represent the effects of smoking or a genetic risk factor for nicotine dependence, the results may reflect the initial effects of cigarette smoking on the brain,” noted senior author Edythe London, a professor of psychiatry and of molecular and medical pharmacology at UCLA’s Semel Institute for Neuroscience and Human Behavior and David Geffen School of Medicine. She added, “This work may also contribute to the understanding of why smoking during this developmental stage has such a profound impact on lifelong smoking behavior.”

The researchers, including first author Angelica Morales, a graduate student researcher in Dr. London’s lab, found differences among younger smokers and non-smokers in an area of the brain known as the insula. The insula is a component of the brain’s cerebral cortex, which is involved in monitoring internal states and decision making. The investigators focused on the insula because it is known to play a central role in the maintenance of tobacco dependence because it contains the highest density of nicotinic acetylcholine receptors within the human cerebral cortex.

The study group comprised 42 participants ranging in age from 16 to 22. Among them, 24 were non-smokers and 18 were smokers. The subjects who smoked began around the age of 15 and smoked fewer than seven cigarettes a day at the time of the study. The investigators took smoking histories, evaluated cigarette craving and dependence, and examined the insula using high-resolution structural magnetic resonance imaging. With a comparison of the cortical thickness of the insula in both groups, the investigators found that the amount of “pack-years” was negatively related to the thickness in the right side of the insula: the more the individual smoked, the thinner that part of the insula. (“Pack years” measures the amount of smoking for an individual. For example, one pack a day for 10 years would result in 10 pack years; smoking two packs a day for 10 years would result in 20 pack years.) The relationship with cortical thickness also held true for the subjects’ level of dependence on cigarettes and the urge to smoke.

“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,” explained Dr. London. She added, “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.”

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