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Puffing on a first cigarette is a rite of passage for many teenagers, but whether it is enjoyable may be partly down to genetics, researchers suggest.
University of Michigan scientists have identified a gene variant found more often in people who said their first cigarette produced a "buzz".
These people were much more likely to go on to become regular smokers, the journal Addiction reports.
The researchers say the finding may help development of anti-smoking drugs.
A person's decision to smoke for the first time, or carry on smoking, is not thought to be governed solely by his or her genes, but a mixture of genes, environmental factors and social pressures.
However, scientists are hoping that by cracking the genetic secrets of nicotine addiction, they could make it easier for people to wean themselves off cigarettes, or even stop them taking up the habit in the first place.
The gene in question, CHRNA5, has already been highlighted by other studies into nicotine addiction, and it has been suggested that it could increase a smoker's chance of developing lung cancer.
The Michigan research, however, suggests that it could be at work from the very first instance of exposure to nicotine.
Genetic data was obtained from 435 volunteers, some of whom were regular smokers, and some who had tried cigarettes but were not currently smokers.
They were quizzed about how they felt about their first smoking experience.