Clinical meaning
Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterized by persistent patterns of inattention, hyperactivity, and impulsivity that interfere with functioning. The neurobiological basis involves dysregulation of catecholamine neurotransmission, primarily dopamine and norepinephrine, in prefrontal cortical circuits responsible for executive function (working memory, inhibitory control, cognitive flexibility, sustained attention, and emotional regulation). Neuroimaging studies demonstrate reduced prefrontal cortical volume, decreased activity in the dorsolateral prefrontal cortex and anterior cingulate cortex, and altered dopamine transporter density. The clinician assesses across multiple settings (home, school/work, social) using validated rating scales (Conners, Vanderbilt, SNAP-IV for children; ASRS for adults) and diagnostic criteria from the DSM-5-TR. Treatment follows a multimodal approach: first-line pharmacotherapy with stimulant medications (methylphenidate or amphetamine-based agents) that increase dopamine and norepinephrine in the synaptic cleft, with second-line non-stimulant options (atomoxetine -- selective norepinephrine reuptake inhibitor; guanfacine/clonidine extended-release -- alpha-2 adrenergic agonists) for patients with contraindications to stimulants, substance use concerns, or intolerable side effects. The clinician monitors growth parameters in children, cardiovascular effects (heart rate, blood pressure), appetite, sleep, and titrates doses to optimize therapeutic response while minimizing adverse effects.