Here we evaluated the association between ADHD and intronic SNPs harboured in, among others, the SNAP25, ADGRL3, FGF1, DRD4, and SLC6A2 genes (Table S1, Supplementary Material) in 113 nuclear families ascertained from the metropolitan area of Barranquilla, Colombia. The gene discussed is SLC6A2; the disease is attention deficit-hyperactivity disorder.