Among them, SLC6A2 gene (OMIM 163970, Ch-Band: 16q12, DNA position: 55.69-55.73 Mb) (19), which encodes a norepinephrine transporter responsible for the reuptake of norepinephrine into presynaptic nerve terminals, has been associated with attention-deficit hyperactivity disorder (20,21). Here, SLC6A2 is linked to attention deficit-hyperactivity disorder.