SLC6A2 and attention deficit-hyperactivity disorder: While we conducted a large number of comparisons and some correction for multiple testing is warranted, it is important to note that when we correct for multiple testing in relation to our primary hypothesis, that is association between SLC6A2 and ADHD in children stratified according to MSDP, the primary result of association (Z = 3.74, P = 0.0002) with rs36021 remains significant even if we apply the overly stringent Bonferroni correction (30 SNPs times two exposure strata, p = 0.002).