SLC6A2 and attention deficit-hyperactivity disorder: The largest class of ADHD pharmacological treatment are central nervous system stimulants (e.g., methylphenidate hydrochloride, lisdexamfetamine dimesylate, amphetamine sulfate, mixed amphetamine salts) that act predominantly by regulating the brain levels of monoamines (mostly dopamine and norepinephrine), drugging the sodium-dependent noradrenaline transporter and sodium-dependent dopamine transporter.