Three independent teams of researchers have discovered genes that may explain why some smokers develop lung cancer rather quickly while others smoke heavily their entire life and never have it.

The research, by teams in the United States, France and Iceland, followed after statistics showing that only fifteen percent of smokers eventually develop lung cancer, which led doctors to blame genetics for developing the disease.

The researchers soured the DNA of more than 35,000 white smokers and non-smokers of European descent, with and without lung cancer, looking for genes that have been linked to smoking.

The results of the research confirm some smokers are indeed more vulnerable to lung cancer because of their DNA profile. Also, the same DNA profile is blamed for people becoming addicted to nicotine, which means the findings could eventually lead to better ways to prevent and treat nicotine addiction and lung cancer, the biggest cause of cancer-related death globally in men and the second most common in women.

“It opens the possibility that treatments that block these genes could be very beneficial as a treatment strategy against lung cancer, as well as against addiction,” Paul Brennan of the International Agency for Research on Cancer in Lyon, France, told reporters, according to Reuters.

“We view this as a double whammy. If a smoker has this particular variant, it increases their risk for lung cancer, and it also appears to increase their difficulty of giving up smoking,” said Chris Amos, the M.D. Anderson researcher who led one of the studies.

The studies implicate a genetic variation located near a cluster of genes on chromosome 15 that are involved in the body’s response to nicotine. The studies found that smokers with one of the genetic variant raised their lung cancer risk by 28 percent, while those with both – about 10 percent of the white population – had an increased risk of 80 percent.

People who never smoked but had the genetic quirk were not more susceptible to lung cancer.

“Smoking – it’s the overwhelming risk factor whether you have one or two or no variants,” Dr. Kari Stefansson, chief executive officer of decode Genetics in Iceland and author of the largest of the three studies said during a conference call this week.

The researchers also found that about 50 percent of Caucasians of European descent have the genetic variation, which is believed to be much less common in people of African or Asian descent. Investigators are already conducting studies involving them trying to identify genetic abnormalities that increase the risk of lung cancer in those populations.

What’s there to understand for all of us is what doctors tell us about cigarettes in the first place: if you don't smoke, don't start, and if you do smoke, try to quit.

“It is never safe to smoke, whether you have these gene variants or not,” said Dr. Margaret Spitz, who chairs M.D. Anderson's department of epidemiology and is one of the study's authors.

The good news is that smoking has been declining in the U.S. According to the Centers for Disease Control and Prevention, in 2006, 20.8 percent of U.S. adults were cigarette smokers and that means less than half the percentage in 1965.

Also, airplanes, workplaces, restaurants and bars in many regions have gone smoke-free, but the consequences of an era when smoking was more prevalent still haunt us. More than 160,000 Americans die of lung cancer each year. Smoking is also the leading cause of heart disease, the number one killer in the developed world, and emphysema.

The findings of the three studies were published Thursday in the journals Nature and Nature Genetics.