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Study of smokers’ genes yields age-related addiction factor

CorrespondentApril 28, 2013 

Dan Belsky is a postdoctoral fellow at the Duke University Center for the Study of Aging and Human Development.

DUKE UNIVERSITY

Smoking – undeniably dangerous and addictive – is difficult to quit. According to the U.S. Department of Health and Human Services and the National Institute on Drug Abuse, the nicotine in cigarettes may be as addictive as heroin or cocaine. Despite this, the Centers for Disease Control and Prevention cite that approximately 69 percent of smokers want to kick the habit.

Researchers from Duke University’s Center for the Study of Aging and Human Development may have found why some smokers struggle to quit more so than others, and why it may be especially important to prevent teens and young adults from smoking in the first place.

Dan Belsky, who received his Ph.D. from UNC-Chapel Hill’s Gillings School of Public Health and is now a postdoctoral fellow at Duke, led the study published in March in JAMA Psychiatry. Belsky and his team examined differences in genes that affect the human brain’s ability to respond to and metabolize nicotine. The researchers found variations in these genes among thousands of adult smokers, and developed a “risk score” that could accurately predict whether individuals would become heavy smokers.

“The variants in our genetic risk score were discovered in genome-wide association studies. These studies scanned the genomes of tens of thousands of adult smokers to identify genetic variants that were more common in heavy smokers,” Belsky said.

“Essentially, these studies compare peoples’ genomes and their smoking behavior to identify variants that distinguish heavy smokers from lighter smokers.”

The researchers found that those with high genetic risk for smoking addiction were not more likely to start smoking in the first place. Additionally, if they began smoking as adults, they were not more likely to become addicted smokers.

“For individuals who did not smoke regularly until adulthood, being at high genetic risk did not affect their smoking behavior – they were as likely to develop nicotine dependence and struggle with cessation as peers who were at low genetic risk,” Belsky said.

The key finding from the study was that youth and adolescent smokers with high genetic-risk scores were more likely to become addicted.

One theory is that the smoking addiction genes may more adversely affect the brains of teens and young adults, which are changing and not fully developed.

“Our study cannot address that question. We do know that adolescence is a time when the brain is growing and developing, and may be especially sensitive to the environment,” Belsky said.

Whether teens and young adults with high genetic risk for smoking addiction are more affected because of their developing brains, or for some other reason, Belsky’s research underscores the need for smoking interventions targeted toward these groups.

“Nicotine is addictive for everyone,” Belsky said. “Our results suggest that cigarette smoking may be more addictive for individuals who carry certain genetic risk factors.

“Interventions that keep teens from becoming regular smokers will be especially effective. So policies that affect whether and how easily teens can access cigarettes – like those that raise the price of cigarettes or restrict how and where cigarettes can be sold – are supported by this research.”

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