Genetic defect boosts the chances of becoming addicted to tobacco

A genetic defect, which slows the liver's capacity to clear nicotine from the body, boosts the chances of becoming addicted to tobacco, finds research in Tobacco Control. The effects are particularly strong in new, young smokers, the study shows.

The researchers analysed information on smoking habits and symptoms of nicotine dependence, gathered from almost 1200 grade 7 students in 10 schools.

Blood samples were taken to identify genetic profiles, and 228 students who smoked, but were not yet addicted were subsequently monitored for around two years.

During this period, 67 students became addicted to nicotine. Dependency was significantly more likely among those students with the "inactive" gene variants of the CYP2A6 gene (CYP2A6*2 or CYP2A6*4).

They were almost three times as likely to become addicted to tobacco as those with the normal variants of the gene. Those with partially inactive variants of the CYP2A6 gene were not at increased risk of becoming addicted.

Students with the normal gene smoked an average of 29 cigarettes a week. Those with the partially inactive variant smoked 17. But those with the inactive variant, which slowed down nicotine clearance the most, smoked around 12 cigarettes a week.

The authors suggest that slow clearance prolongs the exposure of the brain to nicotine and is likely to make it more intense. This may boost the effects of the physiological processes which lead to dependence/addiction, and result in the requirement for fewer cigarettes to achieve it.

It also means that while young smokers with the slowest variant are likely to smoke less, they are also likely to get hooked more easily than light smokers, say the authors. Previous research has shown that it is much harder for those who become chemically dependent on nicotine to quit smoking.

Contact: Carmen Kinniburgh, Communications Officer, National Cancer Institute of Canada For Dr Jennifer O'Loughlin, Department of Epidemiology, Biostatistics and Occupational Health, McGill University, Montreal, Quebec, Canada Tel: + 1 416 934 5684 Email: [email protected]