Three research teams, writing in the journals Nature and Nature Genetics, each pinpointed two key areas of variation on chromosome 15. Either way, the results for smokers are increased risk of addiction and lung cancer.
The three studies are funded by governments in the U.S. and Europe. The scientists studied the genes of more than 35,000 white people of European descent in Europe, Canada and the United States.
The gene variations govern nicotine receptors on cells and it explains why some people are chain smokers and have lung cancer. Current or former smokers who carry two copies of both variants, one from each parent - about 15 percent of the total - have a raised risk of 70-80 percent.
Though the variants are common in the population - but they only raise lung cancer risk in those who have smoked. Those who carry one copy of each variant have a raised risk of around 28 percent.
Smokers who do not have the variants are still more than 10 times more likely to get lung cancer than people who have never smoked, whose risk is less than 1 percent.
In spite of the health risks and in spite of the growing stigma, one in five adults smoke and many try to quit. However the smoking rate among U.S. adults has dropped from 42 percent in 1965 to less than 21 percent now.
