Smokers have been given more "wiggle room" to blame their addiction on something other than bad habits, following new research which may have identified a group of genes related to nicotine addiction.
An Irish specialist in public health said, however, that while this was an area of interest, it had little impact on the broader public health issue of smoking.
Scientists have been examining the genetic aspects of smoking for years, looking for genes associated with addiction and possible genetic factors that might make some smokers more likely to become ill from their habit. Genetic factors have conclusively been shown to influence smoking initiation and nicotine dependence, but none of the genes involved has been identified.
Now researchers from the US and New Zealand report in the current issue of Molecular Psychiatry that they have discovered regions on six chromosomes that merit further study as possibly containing genes that make people susceptible to nicotine addiction.
The work was done by scientists from the Medical College of Virginia in the US and the Christchurch School of Medicine in New Zealand who carried out a "genome scan". They looked at the DNA of subjects from a large number of families who had nicotine-dependent members. The object is to find genetic match-ups across families that appear to be common to smokers.
The researchers studied a collection of 130 families containing 308 nicotine-dependent individuals from New Zealand and an independent sample from Richmond, Virginia, of 91 families with 211 nicotine addicts.
The New Zealand group provided possible areas associated with smoking on chromosomes 2, 4, 10, 16, 17 and 18. Similar studies of the Richmond group provided limited additional evidence for linkage on chromosomes 2, 10, 16, 17 and 18. The researchers acknowledged that the small sample size provided only limited power to detect linkage for smoking, a genetically complex trait that could involve many genes.
"However, the evidence for limited replication in several regions across the two samples suggests that some of these regions may contain genes influencing nicotine dependence and therefore deserve further study," the researchers conclude.
Dr Fenton Howell, of the North Eastern Health Board and a board member of ASH Ireland, said there was little to learn from this type of study.
"It is an issue of interest but not of major public health interest," he said. "It doesn't predict who will become addicted and who won't," although in time such genetic work might be able to contribute to new treatment methods to overcome nicotine addiction.
Smoking in Ireland is on the increase, according to Ms Valerie Coughlan of ASH Ireland. Figures for smoking adults had reached a low of 28 per cent but had crept back to 30 per cent, she said.
