We next sought replication for our top SNPs (see Table S1 in the online data supplement). To obtain 100 independent SNPs, we linkage disequilibrium pruned the GWAS data set using PLINK. For pairs of SNPs less than 1 Mb apart with r2>0.2, only the most significant SNP in the Cardiff GWAS in each pair was retained, leaving a total of 60 SNPs. No significant excess signal was observed among these SNPs in the ADHD Genetics Consortium meta-analysis data set (Simes p=0.176, Fisher's p=0.159) or in deCODE (Simes p=0.291, Fisher's p=0.621), or when both data sets (all published reports) were meta-analyzed (Simes p=0.135, Fisher's p=0.095). The individual p values for each of the 60 independent SNPs from these analyses are listed in Table S2 in the online data supplement. The individual p values for the top 100 Cardiff SNPs (see Table S1 in the online data supplement) and the p values from meta-analysis of the Cardiff ADHD GWAS, ADHD Genetics Consortium meta-analysis, and deCODE data sets are listed in Table S3 in the online data supplement. In the combined analysis of all data, no marker SNPs approached genome-wide significance (pmin=6.38×10–6 at rs11698703).
