Can't quit smoking Your GENES might be to blame, rather than a lack of willpower
Scientists have found genes that make some people more likely to smoke
Those affected are more easily hooked as teenagers and then smoke moreAs adults, they find it harder to quit the habit than those with different genes
20:00 GMT, 27 March 2013
20:01 GMT, 27 March 2013
Scientists have found that some genes increase a person's likelihood of becoming a heavy smoker
Genes, rather than feeble willpower, may be the reason why some people just can't stop smoking.
Scientists have identified genetic variants that increase a person's likelihood of becoming a lifelong heavy smoker.
Those affected are more easily hooked as teenagers and quickly progress to smoking 20 or more cigarettes a day.
As adults, they find it harder to quit the habit than individuals with a different genetic make-up.
Researchers studied almost 1,000 New Zealanders from birth to the age of 38 to identify those at a greater genetic risk of smoking.
Participants with a high-risk genetic profile were more likely to smoke every day as teenagers.
At 38, they had smoked heavily for more years, were more susceptible to nicotine addition, and were more likely to have failed in attempts to quit.
'Genetic risk accelerated the development of smoking behaviour,' said study leader Dr Daniel Belsky, from Duke University in Durham, U.S.
'Teens at a high genetic risk transitioned quickly from trying cigarettes to becoming regular, heavy smokers.'
Genetic make-up did not affect whether or not a person would try smoking for the first time. But for individuals who did try cigarettes, having high-risk variants increased the chances of heavy smoking and tobacco dependence.
The results, reported in the journal JAMA Psychiatry, are based on genetic risk scores derived from previous studies that scoured the whole genetic code for associations with smoking.
Alterations in the DNA in and around genes that affect the brain and body's responses to nicotine were more common in the heaviest smokers.
How the specific variants affect gene function is not yet known.
DNA samples from the New Zealand group of 880 men and women of European descent were checked to see if they matched the smoking risk profile.
In total, 70 per cent of the participants had tried smoking, but this was not related to genetic risk.
Those who smoked just one or two cigarettes a day, or only lit up at weekends, had an even lower genetic risk than non-smokers. But a strong association was seen between having a high-risk genetic profile and problem smoking.
Among teens who had tried cigarettes, those with the genetic variants were 24 per cent more likely to become daily smokers by the age of 15, and 43 per cent more likely to be smoking a 20-pack a day by 18.
As adults, people with high-risk genetic
profiles were 27 per cent more likely to become nicotine dependent and
22 per cent more likely to fail at quitting.
Those affected are more easily hooked as teenagers and quickly progress to smoking 20 or more cigarettes a day. As adults, they find it harder to quit
By the age of 38, a heavy smoking study participant with a high-risk genetic make-up had smoked about 7,300 more cigarettes than the average smoker.
Those who did not become regular heavy smokers in their teens appeared to be protected against the perils of tobacco as adults.
'The effects of genetic risk seem to be limited to people who start smoking as teens,' said Dr Belsky.
'This suggests there may be something special about nicotine exposure in the adolescent brain, with respect to these genetic variants.'
Sociomedical expert Professor Denise Kandel, from Columbia University in New York, who was not involved in the study, said: 'Adolescence is indeed a period of high risk for nicotine addiction.
'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.'
The profiling technique is not thought to be sensitive enough to screen out individuals at risk of being enslaved by tobacco.
But the findings have public health implications, the scientists believe.
'Public health policies that make it harder for teens to become regular smokers should continue to be a focus in anti-smoking efforts,' said Dr Belsky.