Role of executive function in ADHD.

Attention-deficit/hyperactivity disorder (ADHD) is a neuropsychiatric disorder characterized by inattention, hyperactivity, and impulsivity. ADHD is commonly treated with behavioral therapy and noradrenergic and dopaminergic pharmacotherapy with psychostimulants such as methylphenidate and dextroamphetamine. Stimulants primarily have dopaminergic and noradrenergic mechanisms of action, with blockade at the dopamine transporter reducing reuptake, resulting in an increase in these neurotransmitters at the synapse. Theoretically, inattention, hyperactivity, and impulsivity in ADHD may be due to underlying executive functioning, alerting, and orienting deficits, and the nonstimulant modafinil could be beneficial in managing symptoms of ADHD by improving these components of attention that accompany wakefulness. Although modafinil exhibits a small degree of dopaminergic action by blocking the dopamine transporter, the major effect of modafinil may be attributable to neuronal activity in the hypothalamus, particularly pertaining to the recently discovered peptides hypocretin 1 and 2 (also known as orexin A and B). However, further placebo-controlled and flexible-dose studies are needed to determine the efficacy of modafinil in treating the symptoms of ADHD in children and adults.