Four hundred eighty-eight EAs in 143 nuclear families were recruited at the same centers and were assessed using the SCID or the Semi-Structured Assessment for Drug Dependence and Alcoholism (SSADDA), as described elsewhere (Gelernter et al., 2005; Pierucci-Lagha et al., 2007; Pierucci-Lagha et al., 2005). Each member of the family sample was evaluated for comorbidity status. A family classified as AD+DD was one in which not all affected family members were AD-only. Thirty-one and 112 families were identified as AD-only and AD+DD families, respectively. The 31 AD-only families, which included a total of 114 subjects, provided insufficient statistical power for analysis, so association analyses were conducted only for the 374 subjects in the AD+DD families. Details of the demographic characteristic for the samples included here are presented in Table 1. The study sample included all subjects presented elsewhere (Yang et al., 2007), but 16 affected subjects from that analysis who had missing DD status were excluded from the present study.
