The World Health Organization estimates that more than 1 billion people smoke worldwide, and that smoking causes nearly 5 million premature deaths every year. Growing scientific evidence suggests a genetic link to nicotine addiction.In findings published in the January issue of Biological Psychiatry, Joel E. Gelernter, M.D., professor of psychiatry, genetics and neurobiology, and colleagues reported on the risk of nicotine dependence in 634 small nuclear families with members who were also dependent on cocaine or opioids. In 507 of the African-American or European-American families, at least two members were nicotine-dependent. The researchers identified one significant genome-wide linkage on chromosome 5 for the African-Americans and a strong linkage on chromosome 7 for the European-Americans. “These data add to the growing evidence for specific locations for genes that influence risk for nicotine dependence,” said Gelernter.