Cigarette smoking is a risk factor for more than two dozen diseases and the single biggest cause of preventable mortality worldwide [1]. Although public awareness of the dangers of smoking is widespread and public health measures such as public building smoking restrictions and increased cigarette taxes have had salutary effects on smoking rates, dependence on nicotine, the major psychoactive component in tobacco, induces most people who start smoking to continue to smoke in spite of their wish to quit [2]. Environmental influences on tobacco dependence including cultural perceptions and economics, low socioeconomic status, peer smoking and maternal smoking during pregnancy are well documented. Nevertheless, twin studies provide strong evidence that a range of diverse smoking phenotypes including age at initiation, intensity, and cessation have a substantial hereditary component 1, 3, 4, 5, 6. Identifying the specific loci that influence smoking behaviors (including initiation, intensity and cessation) could lead to important etiological insights and facilitate the development of treatments to further reduce smoking related mortality.
