By Victoria Stevens, PhD
Every day in the United States, nearly 4,000 young people under the age of 18 smoke their first cigarette, according to the Centers for Disease Control's Youth and Tobacco Use Fact Sheet. About 1,000 of these kids will go on to become daily smokers, which is the next step on the pathway to becoming addicted to nicotine. Over the course of a year, that is 365,000 new daily smokers. About 60%, or almost 220,000, will still be regular smokers 7 to 9 years later.
When they tried that first cigarette, did they expect to become dependent on nicotine and unable to quit smoking whenever they want to? Of course not, because they feel young and invincible. In fact, only 3% of the regular smokers expected to be still smoking 5 years later.
Is nicotine addiction in our genes?
A paper published in JAMA Psychiatry may give some clues to why so many young people continue smoking after that first try. Please note: the research is preliminary, and much more needs to be done before any conclusions are reached and recommendations made. But it's also intriguing.
A group of scientists from the United States, the United Kingdom, and New Zealand used genetics to identify which smokers are likely to become addicted.
The researchers developed a genetic risk score based on the specific code at 6 sites in our DNA which have been associated with risk of heavy smoking in previous research. This risk score was able to predict heavier smoking in 2 studies that included adult smokers, so they applied it to a new group of about 1,000 New Zealanders who had been followed from birth to age 38.
Teenage years pivotal to addiction
During their teenage years, the participants gave information on when they first smoked, if and when they became daily smokers, and if they became heavy smokers (a pack or more per day). When they reached their 20's and 30's, the participants gave information on how many cigarettes they'd smoked in their entire lifetime, nicotine dependence, and the number of times they'd tried to quit smoking but failed. The researchers used all this information to determine a genetic risk score for each of the study participants, and whether this risk score could predict various smoking behaviors.
Teens with a high-risk genetic profile were 24% more likely to become daily smokers by age 15 than were low-risk teens. In addition, the high-risk teens were 43% more likely to smoke at least a pack of cigarettes per day by the time they were 18 years old.
Moving into adulthood, those with a high-risk genetic profile were 27% more likely to be addicted to nicotine and 22% more likely to have failed when trying to quit smoking.
However, for study participants who started smoking as adults, there was no relationship between the genetic risk score and becoming a heavy smoker. This suggests that genetics only plays an important role for smokers who start early in life.
More reason for kids not to try smoking
Overall, this research suggests that genetics can be used to predict which teenager who gives smoking a try is more likely to get hooked. If this relationship between genetic profile and the age when people start smoking holds up, it would provide even more evidence that keeping kids from smoking could significantly decrease the number of adults addicted to smoking and unable to quit.
Should we think about using individual genetic profiling to dissuade kids from experimenting with cigarettes? Maybe someday, but I wouldn't expect it anytime soon for at least 3 reasons. And of course we wouldn't want kids at low risk to think it's okay for them to try smoking!
First, these results are based on a single study of only about 1,000 people, so they would need to be repeated in other countries and across other cultures to truly see if the results would hold up. Second, not everyone agrees which parts of the DNA code should be included in the genetic risk score. For this study, the researchers picked specific regions of DNA, but others would argue that they should have picked different regions; there's no clear evidence that the regions chosen for this study are the best predictors to have used. Third, genetics are only part of the picture and, while they may predict an outcome, they do not determine it. People who have a low risk of becoming addicted may still become addicted, and factors like how available and expensive cigarettes are also play a role in whether people start or continue smoking.
I'm hopeful that future research will address these problems and incorporate other factors, like peer pressure, exposure through marketing, and exposure through friends and family who smoke, into the risk score to increase the strength and precision of its ability to predict whether people will get addicted to smoking and have a harder time quitting.
I'm also excited because studies like this can allow us to find ways to help people quit. One of the main objectives in finding genes like these is that we can develop and target those particular genes with drugs to help them stop smoking. And as personalized medicine progresses, that knowledge could have major benefits. For instance, if we can predict which people are at higher risk of becoming addicted, health care professionals can target them with information that might keep them from ever picking up a cigarette.
Dr. Stevens is strategic director of laboratory services for the American Cancer Society.