Attention-deficit hyperactivity disorders

DEFINITION / DSM-5-TR CRITERIA: Persistent inattention and/or hyperactivity-impulsivity that interferes with functioning or development. Need ≥6 symptoms in children (≥5 in adolescents ≥17 and adults) in a domain; onset of several symptoms before age 12; present in ≥2 settings; symptoms last ≥6 months; clear evidence of impaired social, academic, or occupational functioning; not better explained by another disorder. Presentations: combined, predominantly inattentive, predominantly hyperactive-impulsive.

SYMPTOMS: Inattention: careless mistakes, difficulty sustaining attention, seems not to listen, fails to finish tasks, disorganized, loses things, easily distracted, forgetful, avoids tasks requiring sustained mental effort. Hyperactivity/impulsivity: fidgeting, leaves seat, runs/climbs inappropriately, "driven by a motor," talks excessively, blurts answers, difficulty waiting turn, interrupts others.

EPIDEMIOLOGY / RISK FACTORS: One of the most common childhood neuropsychiatric disorders. Males are diagnosed more than females in childhood (females are more often the inattentive type and are underdiagnosed). Highly heritable (about 70-80%). Other risk factors: prematurity/low birth weight, prenatal tobacco/alcohol exposure, lead exposure, and family history.

PATHOPHYSIOLOGY: Dysregulation of catecholamine (dopamine and norepinephrine) signaling in the prefrontal cortex and frontostriatal circuits, which are involved in executive function, attention, and impulse control. Imaging shows delayed cortical maturation and reduced volume or activity in the prefrontal cortex and basal ganglia.

DIAGNOSIS: Clinical, using history from multiple informants (parents, teachers) and rating scales (e.g., Vanderbilt). Rule out hearing/vision problems, sleep disorders, anxiety, depression, learning disability, substance use, hyperthyroidism, lead toxicity, and seizure disorders (absence).

COMORBIDITIES: Oppositional defiant disorder, conduct disorder, learning disorders, anxiety, depression, tic disorders/Tourette, autism spectrum disorder, and substance use disorder.

TREATMENT: - Preschool (<6 years): parent behavioral training is first-line. - School age and older: medication plus behavioral therapy. - First-line drugs: CNS stimulants (methylphenidate, amphetamine/dextroamphetamine, lisdexamfetamine). They block reuptake and/or increase release of dopamine and norepinephrine. - Adverse effects: decreased appetite/weight loss, insomnia, irritability, headache, abdominal pain, increased HR/BP, tics (may be exacerbated), and rarely psychosis or growth suppression. Risk of misuse and dependence. Contraindications or cautions: structural cardiac disease, substance use history, and uncontrolled psychosis. Screen for cardiac history and family history of sudden death. - Non-stimulants: atomoxetine (selective norepinephrine reuptake inhibitor; not a controlled substance; useful with comorbid substance use or tics; adverse effects include hepatotoxicity and suicidal ideation warning), guanfacine and clonidine (α2-agonists; adverse effects are sedation, hypotension, bradycardia), and bupropion (second-line).

PROGNOSIS: Symptoms persist into adulthood in about 50% or more of cases. Hyperactivity often decreases with age, while inattention and executive dysfunction tend to persist. Untreated ADHD is associated with academic failure, accidents, and substance use.

BOARD PEARLS: (1) Symptoms must be present in ≥2 settings. If only at school or only at home, think of another cause (e.g., a learning disability or family stress). (2) Stimulants are first-line even in patients with comorbid tics (generally safe). (3) A child who stares and is unresponsive for seconds may have absence seizures, not ADHD. (4) Monitor height, weight, HR, and BP on stimulants. (5) Non-stimulant option when substance abuse risk is a concern: atomoxetine.