Tobacco kills over five million people each year and is a risk factor for six of the eight leading cases of death worldwide (2008). Although the health risks of tobacco are well-known in industrialized nations, smoking prevalence remains at around 20% of the United States adult population (CDC, 2007). It is estimated that cigarette smoking and exposure to tobacco smoke leads to as many as 438,000 early deaths and productivity losses of over $90 billion annually (CDC, 2005). Smoking is a complex behavior mediated by both genetic and environmental factors. Multiple twin studies have provided strong evidence that genetic factors contribute to around 50% of the phenotypic variance for tobacco behaviors (Heath et al., 1998; Hopfer et al., 2001; Swan and Carmelli, 1997; Swan et al., 1997; Young et al., 2006). The identification of genes which contribute to nicotine addiction is important for our understanding of an individual’s unique risk factors and improved understanding of the underlying biology.
