Demographic, behavioral, and metabolism metric characteristics of the COGA and COGEND samples are presented in Table 1. The primary COGA sample of young adult daily smokers consisted of 506 European American individuals from 431 nuclear families from 310 extended families. The mean age at last interview was 24, 43% were female, and 92% came from families at high-risk for alcoholism, with 37% meeting the criteria for lifetime DSM-IV alcohol dependence. Among these daily smokers, 61% were nicotine dependent, 33% smoked within 5 minutes after waking, and 26% smoked greater than 20 cigarettes per day (Figure 1 and Table 1). Twenty-six percent of the young adults were slow metabolizers, and the distribution of the metabolism metric (Figure S1) was similar to that seen in other samples (Bloom et al., 2012; Chen et al., 2014).
