Attention-Deficit/Hyperactivity Disorder (ADHD)
Persistent inattention and/or hyperactivity-impulsivity present before age 12 with cross-setting impairment.
Also known as: ADHD, attention deficit, ADD, hyperactivity
Overview
A neurodevelopmental disorder characterized by a persistent pattern of inattention and/or hyperactivity-impulsivity interfering with functioning or development, with several symptoms present before age 12 and across >=2 settings.
Epidemiology
Childhood prevalence ~5-7%; adult prevalence ~2.5-4%. Male-to-female ratio ~2:1 in childhood; narrows in adulthood. Highly heritable (~75%).
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Risk factors
- Family history (first-degree relative ~5x risk)
- Prenatal exposure: nicotine, alcohol, prematurity, low birth weight
- Lead exposure, traumatic brain injury
- Male sex (in childhood diagnostic samples)
Pathophysiology
Frontostriatal and frontoparietal dysfunction with reduced dopaminergic and noradrenergic signaling. Delayed cortical maturation in prefrontal regions. Reduced default-mode suppression during attention tasks.
Clinical presentation
Symptoms
- Inattention: careless mistakes, difficulty sustaining attention, doesn't listen, fails to follow through, organization difficulties, avoids sustained mental effort, loses things, easily distracted, forgetful
- Hyperactivity-impulsivity: fidgets, leaves seat, runs/climbs inappropriately, can't engage quietly, 'on the go', talks excessively, blurts answers, can't wait turn, interrupts
- Adults: internal restlessness, procrastination, difficulty with time management, executive dysfunction
Signs / physical exam
- Restlessness or distractibility evident in interview
- Collateral history from parent/teacher/partner is essential — ADHD is a cross-setting diagnosis
Differential diagnosis
- Anxiety disorder — Concentration deficits secondary to worry; symptoms newer, situational
- MDD / bipolar depression — Episodic; mood disturbance predominates
- Substance use disorder — Symptoms in temporal relationship to use; especially stimulants, cannabis
- Hyperthyroidism — Tremor, weight loss, suppressed TSH
- Learning disability — Domain-specific academic deficit without pervasive inattention
- Autism spectrum disorder — Social communication deficits and restricted/repetitive behaviors; often co-occurs with ADHD
- OSA / poor sleep — Daytime inattention from sleep fragmentation; screen with sleep history
Diagnostic workup
Diagnostic criteria
DSM-5-TR: (A) >=6 inattention and/or >=6 hyperactivity-impulsivity symptoms for >=6 months in children, or >=5 for individuals age 17 and older; (B) Several symptoms present before age 12; (C) Present in >=2 settings; (D) Clear interference with functioning; (E) Not better explained by another disorder. Specify combined, predominantly inattentive, or predominantly hyperactive-impulsive presentation. Validated rating scales: Vanderbilt (children), ASRS (adults), Conners.
Labs
- TSH, CBC if suggested by history
- Pre-stimulant: BP, HR; cardiac history including family history of sudden death; ECG only if cardiac concerns
- Urine drug screen if substance use suspected
Imaging
- Not routinely indicated
Diagnostic algorithm
| Class | Examples | Pearls |
|---|---|---|
| Stimulant — methylphenidate | methylphenidate IR/ER, dexmethylphenidate | First-line; titrate weekly; monitor BP/HR/sleep |
| Stimulant — amphetamine | lisdexamfetamine, mixed amphetamine salts, dextroamphetamine | First-line; lisdexamfetamine prodrug with lower abuse potential |
| Non-stimulant SNRI | atomoxetine, viloxazine | Useful with anxiety, tics, SUD history; 4-6 wks to effect |
| Alpha-2 agonist | guanfacine ER, clonidine ER | Adjunct or monotherapy; helps sleep onset, tics; watch sedation/BP |
Treatment
First-line
- Behavioral parent training and classroom interventions — first-line in preschool age (4-5 years) and adjunct at all ages
- Stimulant — methylphenidate, lisdexamfetamine, mixed amphetamine salts (first-line pharmacotherapy school-age and older); titrate to effect over weeks
- School accommodations (IEP/504); psychoeducation; sleep regularity; exercise
- Adults: CBT for ADHD; coaching; organizational supports
Second-line / adjunct
- Non-stimulant: atomoxetine (selective norepinephrine reuptake inhibitor, NRI), viloxazine; useful in tic disorder, anxiety, SUD history
- Alpha-2 agonist: extended-release guanfacine, clonidine — adjunct or monotherapy in children, especially with sleep onset issues or tic disorder
- Bupropion — off-label in adults with comorbid depression
- Avoid prescribing immediate-release stimulants to patients with active SUD; use long-acting or non-stimulants and consider diversion risk
Complications
- Academic underachievement, occupational instability
- Increased risk of motor vehicle crashes, injuries
- Substance use disorders, especially when untreated
- Comorbid mood, anxiety, learning, and oppositional defiant disorders
- Stimulant side effects: appetite suppression, growth slowing, insomnia, modest BP/HR increases, rare cardiac events in those with structural heart disease
- Misuse and diversion
PANCE pearls
- Cross-setting and pre-age-12 symptoms are required — recent onset in adulthood should prompt search for other causes (substance use, mood, sleep, cognitive decline).
- Stimulants are more efficacious than non-stimulants but require monitoring for BP/HR, appetite, sleep, and growth.
- Reassess every 6-12 months — many children continue to benefit into adulthood; some achieve symptom remission and may taper.
- Routine pre-treatment ECG is not required in low-risk children per AAP; obtain ECG/cardiology referral with positive cardiac history or exam.
References
- AAP 2019 — AAP Clinical Practice Guideline for the Diagnosis, Evaluation, and Treatment of ADHD in Children and Adolescents (2019)
- AACAP / APA — AACAP Practice Parameter for the Assessment and Treatment of ADHD; APA guidance for adult ADHD
- DSM-5-TR — American Psychiatric Association. DSM-5-TR (2022)
- MTA Study — The MTA Cooperative Group. A 14-month randomized clinical trial of treatment strategies for ADHD. Arch Gen Psychiatry 1999
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