attention deficit hyperactivity disorder

**Definition/Diagnosis (DSM-5-TR):** Persistent inattention and/or hyperactivity-impulsivity that interferes with functioning or development. Requires ≥6 symptoms in children (≥5 for age ≥17 and adults), lasting ≥6 months, several symptoms present before age 12, present in ≥2 settings (home, school, work), clear impairment in functioning, and not better explained by another disorder. Presentations: predominantly inattentive, predominantly hyperactive-impulsive, or combined (most common).

**Epidemiology:** One of the most common childhood neuropsychiatric disorders (about 5–7% of children). More common in boys (about 2:1). Girls are more often the inattentive type and are frequently underdiagnosed. It often persists into adulthood (about 50–60%).

**Pathophysiology:** Highly heritable (about 75%). Dysfunction of the prefrontal cortex and fronto-striatal circuits, with decreased dopamine and norepinephrine signaling. Imaging may show decreased frontal lobe activity and mildly reduced brain volume. Risk factors include prematurity, low birth weight, prenatal exposure to tobacco, alcohol, or lead, and a family history.

**Clinical features:** - Inattention: careless mistakes, difficulty sustaining attention, doesn't seem to listen, fails to finish tasks, disorganized, loses items, easily distracted, forgetful. - Hyperactivity: fidgeting, leaving seat, running or climbing excessively, "driven by a motor," talks excessively. - Impulsivity: blurts out answers, difficulty waiting turn, interrupts others. - Associated: poor academic performance, accidents/injuries, and low self-esteem.

**Comorbidities:** Oppositional defiant disorder, conduct disorder, learning disorders, anxiety, depression, tic disorders/Tourette, and substance use disorders. Also consider bipolar disorder.

**Workup/Differential:** Diagnosis is clinical, using history and rating scales (e.g., Vanderbilt, Conners) from parents and teachers. Rule out hearing/vision problems, lead poisoning, hyperthyroidism, sleep disorders (OSA), seizures (absence), anxiety/depression, learning disability, abuse/trauma, and medication effects. Consider an ECG or cardiac history before stimulants if there are cardiac risk factors or a family history of sudden death.

**Management:** - Age 4–5: parent training in behavior management is first line. - Age ≥6: medication plus behavioral therapy. Stimulants are first line. - Methylphenidate and amphetamines (Adderall) block reuptake of dopamine/norepinephrine and, with amphetamines, also increase release. - Adverse effects: decreased appetite/weight loss, insomnia, growth slowing, headache, abdominal pain, tachycardia/hypertension, tics (may worsen), rare psychosis, and risk of misuse/dependence. - Nonstimulants (second line, or if stimulants are contraindicated or there is substance abuse, tics, or anxiety): - Atomoxetine: selective norepinephrine reuptake inhibitor (SNRI); not a controlled substance. Watch for hepatotoxicity and suicidality. - Guanfacine and clonidine: α2-agonists; adverse effects include sedation, hypotension, and bradycardia. Do not stop clonidine abruptly because of rebound hypertension. - Bupropion and TCAs are alternatives in adults.

**High-yield pearls:** - Symptoms must be in ≥2 settings. If symptoms occur only at school or only at home, think of other causes (e.g., learning disability, family stress). - ADHD is a clinical diagnosis. Neuroimaging and labs are not diagnostic. - Stimulants can worsen anxiety and tics but are generally still safe in tic disorders. Weigh the risks. - Monitor height, weight, BP, and HR on stimulants. Drug holidays can help with growth suppression. - In patients with a substance use history, prefer nonstimulants.