ASD: autism spectrum disorders, SSRIs: selective serotonin reuptake inhibitors, SNRIs: serotonin-norepinephrine reuptake inhibitors, TCAs tricyclic antidepressants, DAT: dopamine transporters, NET: norepinephrine transporters, ADHD: attention deficit and hyperactivity disorder, KCC2: K-Cl co-transporter, NMDA: N-methyl-D-aspartate. The gene discussed is SLC6A2; the disease is attention deficit-hyperactivity disorder.