Genes affect smoking behaviour

For some people, quitting smoking could be especially difficult because their dependence may be explained in part by genetics, three new studies suggest.

The researchers from the three studies analysed the DNA profiles of more than 140,000 people - smokers and non-smokers. They also studied whether genetic variants affect whether people start smoking, how much they smoke and whether they are able to quit.

For the first study, researchers studied 74,053 people and found three genetic regions that were associated with the number of cigarettes smoked per day. One region was associated with smoking initiation, and one variant was associated with smoking cessation. The genetic variants on chromosome 15 that were associated with heavy smoking lie within a region that contains nicotine receptor genes, which other scientists have previously associated with nicotine dependence and lung cancer.

In the second study, researchers from UK tested the human genome for genes associated with cigarette smoking. Based on an analysis of more than 46,481 people, it was found that a group of genes on chromosome 15q25 is associated with the number of cigarettes that people smoke per day.

The third study, from researchers in Iceland, also looked through the human genome to find genes associated with the number of cigarettes a person smokes daily. Using data from more than 70,000 smokers, it confirmed that genes on chromosome 15 were linked to tobacco use. The researchers also found two genes, CYP2A6 and CYP2B6, that were involved in nicotine metabolism and two others, CHRNB3 and CHRNA6, which play a role in how the body processes nicotine. It was found that some of these gene regions are also associated with a predisposition to lung cancer.

Too many people think of smokers as having self-imposed diseases. But the above findings suggest a genetic predilection responsible for nicotine dependence and smoking addiction.

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