DNA samples for our ADHD case subjects were genotyped on the Illumina (San Diego) Human660W-Quad BeadChip according to the manufacturer's instructions. Comparison subjects were genotyped by Wellcome Trust Case Control Consortium–Phase2 using the Illumina Human 1.2M BeadChip. BeadStudio (version 2.0) was used to call genotypes and inspect cluster plots. Analysis was based on 518,511 SNPs that were present on both chips.
