statistical power. Because the VAND panel was originally designed to study both smoking initiation and nicotine dependence [Sullivan et al., [2001]; Chen et al., [2004], [2007]], never smokers were included. There were two groups of smokers in the VAND panel, one group was with low nicotine dependence (defined as those with an FTQ scores between 0 and 2) and the other group was with high nicotine dependence (defined as those with an FTQ score between 7 and 11). The VAANX panel was initially selected for the study of anxiety and neuroticism [Hettema et al., [2006]]. The inclusion criterion was the top and bottom 25 percentile of a genetic factor score - a composite index representing several internalizing anxiety disorders and the personality trait of neuroticism [Hettema et al., [2006]]. We denoted this composite index as internalizing anxiety and neuroticism genetic factor (IANGF) score. In this study, only regular smokers (defined as those who used at some point in their lives an average of at least seven cigarettes per week for a minimum of 4 weeks) were included (Table I and Supplementary Figure S1).
