No genome-wide significant (or suggestive) ADHD-associated SNPs assigned to MARK2 (minimum p = 0.02), SLC7A8 (minimum p = 0.3), GART/SON (minimum p = 0.029), USP31 (minimum p = 0.069), or LOC100130015 (minimum p = 0.011) were seen in the GWAS meta-analysis, indicating there is no evidence of pleiotropy for these mQTLs. Here, USP31 is linked to attention deficit-hyperactivity disorder.