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.
"It appears that for people who have a certain genetic make-up, the initial physical reaction to smoking can play a significant role in determining what happens next"
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.
Practical uses
Regular smokers were far more likely to have the variant version of the gene and more likely to report that their first smoking experience was pleasurable.
Professor Ovide Pomerleau, who led the research, said: "It appears that for people who have a certain genetic make-up, the initial physical reaction to smoking can play a significant role in determining what happens next.
"If cigarette smoking is sustained, nicotine addiction can occur in a few days to a few months - the finding of a genetic association with pleasurable early smoking experiences may help explain how people get addicted."
Dr Marcus Munafo, from Bristol University, said that while the study was interesting, any treatments or tests based on the gene variant would be some way off.
He said: "It's interesting to see research which helps us join the dots on the whole mechanism of nicotine addiction, but in practical terms, we have, for now, to carry on doing what we are currently doing to help smokers."
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