We implemented case control and family study designs. All relevant institutional review boards approved the study protocol and related materials, and all subjects, who were paid for their participation, provided written informed consent. All subjects included in this study were also included in our previous study (Yang et al., 2007) but this sample is completely distinct and nonoverlapping from our previous study of this gene cluster in ND (cf. Gelernter et al 2006, page 3504, Subject recruitment and assessment).
