Numerous large twin studies for alcohol-related behaviors have consistently shown that heritability of alcohol abuse and dependence ranges from 50% to 70%.8 A similarly high heritability also is seen across other alcohol-related behaviors, including heavy consumption and `problem' drinking.8 Meta-analysis of the twin studies shows that both genes and environment are important in smoking-related behaviors, with an estimated mean heritability of 0.50 for smoking initiation and 0.59 for nicotine dependence (ND).4 Genetic factors have a larger role in initiation than in persistence in women, whereas the opposite is observed in men.4,9
