Genotype data for the top 100 SNPs from the present GWAS were requested from the ADHD genetics consortium (10) and deCODE. In these samples, we tested for enrichment of association of our top 100 SNPs after linkage disequilibrium pruning (see the online data supplement). There were 204 samples from the present GWAS that overlapped with those included in the ADHD genetics consortium GWAS meta-analysis. Overlap was statistically accounted for in the analysis (see the online data supplement). There was no overlap between those two data sets and that of deCODE. Two methods were used to test for enrichment of association signal in the combined set of SNPs. The first of these was the Simes test (27), a more powerful and less conservative version of the Bonferroni method, which tests SNPs one at a time. The other was Fisher's method for combining p values, which aggregates the evidence for all SNPs simultaneously. Since odds ratios must be in the same direction as our GWAS to count as replication, one-sided p values were used in the analysis. Enrichment was tested in the
