GENETIC AND ENVIRONMENTAL CONTRIBUTIONS TO SMOKING

We estimate the magnitude of genetic and shared environmental contribu tions to risk of initiation and maintenance of smoking Genetic models were fitted to data from 2 204 male-male monozygotic and 1 793 male-ma le dizygotic twin pairs from the Vietnam Era Twin Registry who respond ed to smoking questions on a 1987 mail and telephone survey. The best fitting model allowed for both genetic and shared environmental effect s on smoking initiation, accounting for 50% and 30% of the variance in risk, but allowed for only genetic effects, (accounting for 70% of th e variance in risk), on persistence in smoking among those who had bec ome regular smokers. This finding of a major genetic influence on smok ing persistence confirms similar results from studies in Scandinavia a nd Australia. The role of heritable traits such as nicotine sensitivit y should be addressed in smoking prevention and cessation efforts.