Cigarette smoking is highly prevalent throughout many populations around the globe. Despite increasing awareness of the risks associated with smoking, the World Health Organization (1999) estimated that 1.1 billion people still smoke, and predicted that by 2025, the number will increase to 1.6 billion worldwide. Thus, understanding various factors that influence smoking behavior is critical to the prevention and cessation of smoking. Although the etiology of smoking behavior is complex, a genetic contribution to smoking behavior, presumably based on addiction to nicotine, is well established from twin and adoption studies (1, 2). Genetic linkage analysis can be a useful design to detect genes that segregate in families, including common variants, multiple rare variants within one locus, and copy number variation.
