Genetic epidemiology of smoking behavior and nicotine dependence.

The genetic epidemiology of smoking behavior and nicotine dependence is reviewed. Twin, family and adoption studies show consistent evidence for genetic effects on many aspects of smoking behavior and nicotine dependence, while molecular genetic analyses have only recently identified genes consistently associated with nicotine dependence and amount smoked. Further studies with more sophisticated phenotypes, larger sample sizes and better measures of the environment are needed.