In the gene-based analysis six genes were exome-wide significantly associated with ADHD + DBDs, including two implicated by variants in or near the genome-wide significant locus on chromosome 11 (RRM1 and STIM1) and with three (ST3GAL3, KDM4A, and PTPRF) out of the remaining four located in or near the genome-wide significant locus on chromosome 1. This evidence concerns the gene KDM4A and attention deficit-hyperactivity disorder.