March 28, 2013
Genetic Markers For Smoking May Help Predict Who Gets Hooked
Brett Smith for redOrbit.com - Your Universe Online
According to a new study in JAMA Psychiatry, a team of international scientists has developed a genetic profile that indicates a greater risk for a teenager's progression into becoming a lifelong heavy smoker.
People who share the genetic profile showed a greater risk of daily smoking as teenagers and then progressing more rapidly to smoking a pack a day or more as adults, the study said. High-risk individuals who were assessed in their late thirties were found to have smoked heavily for more years, have a greater nicotine dependence and were more likely to have multiple failed in attempts to quit smoking.
"Genetic risk accelerated the development of smoking behavior," said study co-author Daniel Belsky, a post-doctoral research fellow at Duke University. "Teens at a high genetic risk transitioned quickly from trying cigarettes to becoming regular, heavy smokers."
The research team began by looking at earlier studies to identify genetic signifiers of heavy smokers. In particular, they examined their own 38-year study of 1,000 New Zealanders to identify whether individuals at high genetic risk picked up a smoking habit more quickly as teens and if they had a more difficult time quitting as adults.
In order to rank individuals, the researchers developed a "genetic risk score" based on prior genome-wide associations of adult smokers. After identifying the genetic variants most common to heavy smokers, the team noted that these variants affect how the brain and body respond to nicotine. However, they were unable to determine how the specific variants affect the particular gene where they are located.
After identifying the genetic variants, the team examined the data culled from their New Zealand study to see if an individual´s genetic risk score could predict things like who began smoking, who progressed to heavy smoking, who became addicted and who experienced relapse after attempting to quit.
The researchers found that genetic risk factors were not associated to whether a person tried smoking, as 70 percent of all participants had. One group of non-addicted smokers emerged in the study — the so-called "chippers" — who smoke once or twice a day or at social gathering. These individuals showed an even lower genetic risk than nonsmokers.
The analysis showed that teens with a high-risk genetic profile who tried cigarettes were 24 percent more likely to become daily smokers by age 15 and 43 percent more likely to average a pack-a-day or more by age 18.
As adults, these high-risk individuals were 27 percent more likely to become nicotine addicts and 22 percent more likely to fail at quitting.
"The effects of genetic risk seem to be limited to people who start smoking as teens," said Belsky. "This suggests there may be something special about nicotine exposure in the adolescent brain, with respect to these genetic variants."
"Adolescence is indeed a period of high risk for nicotine addiction," said Denise Kandel, a professor of sociomedical sciences in psychiatry at Columbia University, who was not involved in this study.
"The results illustrate why adolescence is of crucial importance for the development and targeting of prevention and intervention efforts. How this genetic risk affects brain functions, which in turn affect reactions to nicotine, remains to be determined."
"Public health policies that make it harder for teens to become regular smokers should continue to be a focus in antismoking efforts," Belsky said.