In the second instance we report a genetic influence on the expression of SERT, along with potential, small effects of TPH2, 5-HT1E, 5-HT2A, DAT1, DA D1 and D4 receptors prominently expressed in limbic and association cortices and implicated in the initiation of impulsive processes and their expression by young people with ADHD. This evidence concerns the gene SLC6A4 and attention deficit-hyperactivity disorder.