London: Struggling to quit smoking? Blame your genes, as scientists claim three genetic mutations make it hard for smokers to kick the butt.
A report based on three studies that compared the DNA of more than 140,000 people found that the desire to give up smoking is down to a person`s genes rather than willpower.
The findings, published in journal Nature Genetics, could lead to more personalised - and ultimately more effective - treatments that help people stub out their cigarettes.
Two of the three studies identified regions associated with the number of cigarettes smoked per day. The regions had four genes -- two genes linked with nicotine dependence and two others that regulate nicotine metabolism in the body.
Mutations in these genes are associated with a minor rise in the number of cigarette a person smokes per day – about half a cigarette a day -- but around 10 per cent increase in
risk of lung cancer compared with non carriers, the Daily Mail reported.
Lead author Professor Kari Stefansson, a neurologist at deCODE genetics in Reykjavik, Iceland, said: "To some degree these variants suggest that those persons for whom
nicotine is more addictive are driven to smoke more, increasing their exposure to environmental risk.
"But given the quite substantial corresponding increases in risk of lung cancer it may also be that they make people more susceptible to the noxious effects of tobacco smoke,"
The third study by a team led by Clyde Francks from the University of Oxford identified variants of three genes on chromosome 15 that make people more prone to nicotine
Nicotine is the primary chemical responsible for smoking addiction.
Francks said, "Smoking behaviour and nicotin e dependence are multi-factorial traits with substantial genetic influences. There is an urgent need to better understand the molecular neurobiology of nicotine dependence in order to design targeted, more effective therapies.
Stefansson said, "What is clear is that these variants -- which are all near genes that encode nicotine metabolising enzymes and receptors -- are giving us a solid starting point
for finding answers to advance personal and public health."
"These findings have provided further new insights into the biology of smoking behaviour," Francks concluded.