Synapsin III (Syn III) is a neuronal phosphoprotein regulating striatal dopaminergic neurotransmission in the adult brain [1,2] and is involved in psychiatric disorders associated with dysfunctions of brain dopaminergic systems, including attention deficit and hyperactivity disorder (ADHD) [3,4,5,6]. Here, SYN3 is linked to attention deficit-hyperactivity disorder.