Smokers who find it hard to stop or quit smoking cigarettes may be at the mercy of their genes, say scientists. Scientists also identified three genetic mutations that increase the number of cigarettes people smoke a day. Several also appear to be associated with taking up smoking, and one with being able to quit.Three studies published online in Nature Genetics compared the DNA of more than 140,000 people and discovered the desire to give up is down to your genes rather than willpower.

Two of them found regions associated to the number of cigarettes smoked per day that include two genes that have been linked with nicotine dependence and two others that regulate nicotine metabolism in the body.

"Smoking is bad for anyone's health. It is even worse for some. To some degree these variants suggest those for whom nicotine is more addictive are driven to smoke more, increasing their exposure to environmental risk".

Many smokers beleive that is they will smoke low tar cigarettes like Winston White cigarettes or Marlboro brand , they are not exposed to the risk of getting ill

"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.

"Smoking behaviour and nicotine dependence are multifactorial 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.

"These findings have provided further new insights into the biology of smoking behaviour." he added.