Genes behind smoking addiction in teens: study

Scientists have identified certain genetic risk factors that may accelerate a teen's progression to becoming a lifelong heavy smoker.
Scientists from the US, the UK and New Zealand examined earlier studies by other research teams to develop a genetic risk profile for heavy smoking.
They also looked at their own long-term study of 1,000 New Zealanders from birth to age 38.
Study participants who had the high-risk genetic profile were found to be more likely to convert to daily smoking as teenagers and then progress more rapidly to heavy smoking (a pack a day or more), the research found.
When assessed at age 38, the higher-risk individuals had smoked heavily for more years, had more often developed nicotine dependence and were more likely to have failed in attempts to quit smoking.

"Genetic risk accelerated the development of smoking behaviour," said Daniel Belsky, from Duke University's Center for the Study of Aging and Human Development and the Duke Institute for Genome Sciences & Policy.

"Teens at a high genetic risk transitioned quickly from trying cigarettes to becoming regular, heavy smokers," Belsky said in a statement.
A person's genetic risk profile did not predict whether he or she would try cigarettes. But for those who did try cigarettes, having a high-risk genetic profile predicted increased likelihood of heavy smoking and nicotine dependence.
The Duke researchers developed a new "genetic risk score" for the study by examining prior genome-wide associations (GWAS) of adult smokers.

These studies scanned the entire genomes of tens of thousands of smokers to identify variants that were more common in the heaviest smokers.
The variants they identified were located in and around genes that affect how the brain responds to nicotine and how nicotine is metabolised, but it is not yet known how the specific variants affect gene function.
Researchers turned to their New Zealand sample and found genetic risk was not related to whether a person tried smoking, which 70 per cent of the sample had.
One reason for this was that so-called "chippers" - smokers who consume cigarettes only on weekends or smoke only one or two per day - had even lower genetic risk than nonsmokers.

Genetic risk was related to the development of smoking problems. Among teens who tried cigarettes, those with a high-risk genetic profile were 24 per cent more likely to become daily smokers by age 15 and 43 per cent more likely to become pack-a-day smokers by age 18.
As adults, those with high-risk genetic profiles were 27 per cent more likely to become nicotine dependent and 22 per cent more likely to fail in their attempts at quitting.