Cigarette smoking commonly co-occurs with alcohol abuse. A meta-analysis of twin studies showed that both genetic and environmental factors affect smoking and smoking-related behaviors (83). In women, the initiation of smoking is influenced largely by genetic factors; in men, the genetic impact is more significant on the persistence of smoking than on the initiation of smoking (83). The heritability of smoking initiation and nicotine dependence is estimated to be 50% and 59%, respectively (83).
