Using QTDT, each tagging SNP was tested for association with parent and teacher DSM-IV subscales and five CPT measurements. We identified two SNPs in SLC9A9 that remained significant after applying an FDR q value threshold of 0.05 to correct for testing 89 SNPs (Table 4 and Fig. 1). None of the 10 DOCK3 tagging SNPs remained significantly associated with any of the 11 quantitative traits examined. The first significant SNP, rs1046706, in the 3′UTR of SLC9A9 was associated with T-scores on the DSM-IV hyperactive-impulsive and total symptom subscales according to the CTRS and the CPT measure, errors of commission (Table 4). The major allele (T) was associated with higher hyperactive-impulsive symptom counts [55.23±10.48 (GG), 61.21±13.68 (TG), 63.09± 13.79 (TT) (mean ± standard deviation)], total symptom counts [56.32±9.99 (GG), 65.38±12.69 (TG), 66.00±12.46 (TT)], and errors of commission [47.56±9.51 (GG), 50.91±10.94 (TG), 52.75±11.25 (TT)]. It is worth noting that rs1046706 was also nominally associated with hyperactive-impulsive (P= 0.001), inattentive (P=0.021), and total symptom scores (P=0.003) according to the CPRS, inattentive scores (P=0.007) according to the CTRS and the CPT measure, hit reaction
