A GWAS of five moderately to strongly heritable quantitative indicators of behavioral disinhibition in a sample of 7188 Caucasians failed to yield any confirmed associations. Although the p-value for the association of one SNP, rs1868152, with one of the phenotypes, Illicit Drug use, was lower than the GWAS standard of 5 × 10-8, we do not consider this a confirmed positive result because the observed p-value of 4.9 × 10-8 was just below the critical threshold of 5.0 × 10-8, which does not take into account the multiple phenotypic tests we ran for each SNP. Our failure to observe any significant effects likely reflects the polygenic nature of the phenotypes we investigated, a conclusion that has now been reached with many other phenotypes (Manolio et al., 2009). Although the power of our design is complicated by the multiple clustered nature of the sample, power must lie between that for a sample of 2300 (i.e., the number of independent families) and 7188 (i.e., the number of individuals) observations. Consequently, with a two-tailed test at p < 5 × 10-8, we have
