The smoking gene: bad news for teens

The researchers have developed a genetic risk profile and tested its accuracy on New Zealand’s possibly most observed and experimented on group: the Dunedin Birth Cohort.

Genetic risk profile

Previous large studies, scanning the entire genomes of tens of thousands of smokers, have identified several variants (located in and around genes that affect how the brain responds to nicotine and how nicotine is metabolised) that are associated with heavy smoking in adulthood. The studies suggest these variants play a role in conversion to daily smoking, progression to heavy smoking and nicotine dependence.

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Exposure to different chemicals can increase your risk of cancer. For example, exposure to the chemicals in tobacco smoke is a major risk factor for the development of lung cancer.

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In a study spanning decades, the researchers used these identified loci (the specific place on a chromosome where a gene is located) to create a genetic risk profile. They then used this profile to identify whether genetically at-risk individuals in the 1037-person Dunedin study group would become heavy smokers. The study group, who are all of a similar age, were evaluated at eight assessments, spanning 11–38 years. These assessments recorded smoking initiation, conversion to daily smoking, progression to heavy smoking, nicotine dependence and how much difficulty they had quitting.

Results of higher genetic risk

The results, published in the journal JAMA Psychiatry, showed that a person’s genetic risk profile had no influence on whether they would try cigarettes in the first place, although a staggering 70% of the sample had.

For those who opened Pandora’s Box, having a higher genetic risk did indeed mean an individual was 24% more likely to become a daily smoker by age 15, 43% more likely to become a pack-a-day smoker by age 18 and persist longer in smoking heavily. They also “developed nicotine dependence more frequently, were more reliant on smoking to cope with stress and were more likely to fail in their cessation attempts,” the researchers wrote in their published paper.

Genetic risk limited to teens

In a press release from Duke University in the States, one of the study’s authors, Dr Daniel Belsky, said, “The effects of genetic risk seem to be limited to people who start smoking as teens. This suggests there may be something special about nicotine exposure in the adolescent brain, with respect to these genetic variants.”

The researchers write that their genetic risk profile isn’t accurate enough to be used for targeted interventions aimed at at-risk teens, but it does highlight the critical adolescent period for nicotine addition.

“Public health policies that make it harder for teens to become regular smokers should continue to be a focus in antismoking efforts,” says Dr Belsky.

The Dunedin Birth Cohort is made up of just over 1,000 people born at Dunedin’s Queen Mary Hospital between 1 April 1972 and 31 March 1973 and still living in Otago at age 3.