replication in a second, family-based sample of 1,095 subjects from 242 families with many alcohol-dependent individuals (Zlojutro et al., 2011). None of the variants were genome-wide significant. Table 7 lists a second GWAS of event-related theta activity conducted by COGA, which seems to have expanded on the family sample of Zlojutro et al., studying 1,560 subjects in 117 densely alcoholic families (S. J. Kang et al., 2012). A genome-wide significant signal was observed in chromosome 21 from multiple SNPs in KCNJ6. This study did not replicate the Zlojutro et al. finding. A subsequent study from our group with a sample of approximately 4,100 (see Section 5.2 and Table 2), failed to confirm either one. These studies from our group, Roussos et al., and COGA represent among the best currently available in electrophysiological endophenotype research; they show that electrophysiological endophenotypes have not protected researchers from the problem of false positives that have been widely observed to plague underpowered studies of complex traits.
