1. Introduction
ADHD is a neurodevelopmental disorder characterized by inattention, hyperactivity, and impulsivity. These symptoms may significantly impair functioning in academic, social, or occupational domains.
2. Epidemiology
- Global prevalence in school-aged children: ~5–7%
- Male-to-female diagnosis ratio: ≈3:1, though females more often present with inattentive symptoms and may be underdiagnosed
- About 2–4% of adults continue to meet diagnostic criteria, though many receive later diagnoses
3. Risk Factors
- Prenatal/perinatal: Premature birth, low birth weight, maternal smoking or alcohol use during pregnancy
- Genetic: ADHD is highly heritable (heritability ~70–80%); family history is a strong predictor
- Environmental: Lead exposure, early childhood adversity, family conflict, traumatic brain injury
- Neurological comorbidities: Neurofibromatosis type 1, other systemic illnesses
4. Neurobiology and Pathophysiology
- Neuroimaging: Reduced volumes in prefrontal cortex, basal ganglia, cerebellum, corpus callosum
- Neurocircuitry dysfunction: Altered frontostriatal and frontoparietal connectivity
- Neurotransmission: Dopaminergic and noradrenergic hypofunction—basis for pharmacotherapy targeting these pathways
5. Diagnostic Criteria (DSM‑5)
At least six symptoms of inattention and/or hyperactivity–impulsivity must be present for ≥6 months to a degree inconsistent with developmental level:
Inattention (≥6 symptoms):
- Distractibility, disorganization, difficulty with sustained focus or follow-through
Hyperactivity–Impulsivity (≥6 symptoms):
- Fidgeting, excessive talking, difficulty remaining seated, impulsive actions
Symptoms must appear before age 12, occur in ≥2 settings, and impair functioning.
6. Clinical Presentation
Key Findings:
- No diagnostic physical signs
- Mental status: Restless, impulsive speech and thought, distractibility; cognition often characterized by executive dysfunction, short-term memory issues; remote memory usually preserved
- Mood typically unaffected, but depressive and anxiety disorders are common comorbidities
7. Differential & Comorbid Conditions
- Behavioral: Oppositional defiant disorder, conduct disorder (common overlap)
- Psychiatric: Depression, anxiety, OCD
- Neurodevelopmental: Learning disabilities, Tourette syndrome, autism spectrum disorder
- Others: Sleep disorders, substance use disorders
8. Management & Treatment
a) Behavioral Interventions
- First-line in preschoolers and mild cases
- Parent training, school-based interventions, executive skills coaching, sleep hygiene
b) Pharmacotherapy
Indications: Moderate-to-severe ADHD impacting functioning
| Medication Class | Examples | Mechanism | Notes |
|---|---|---|---|
| Psychostimulants | Methylphenidate, amphetamine derivatives | ↑ Dopamine & norepinephrine | First-line; 70–80% response; monitor BP/HR/appetite/sleep |
| Non-stimulant SNRI | Atomoxetine | ↑ Norepinephrine | Useful for coexisting tic, anxiety, substance use; delayed onset; monitor for rare hepatitis, suicidality |
| Alpha‑agonists | Clonidine, guanfacine | Postsynaptic α2A receptor agonists | Adjunctive, especially with tics or insomnia; sedation/hypotension common |
| Others | Bupropion, modafinil (off-label) | Various | Consider for coexisting depression or stimulant intolerance |
c) Combined Approach
- Most effective ADHD treatment combines pharmacotherapy with behavioral and psychosocial interventions
9. Prevention Strategies
- Encourage healthy prenatal environments (avoidance of maternal smoking and alcohol)
- Limit early childhood exposure to neurotoxins
- Early developmental interventions and limiting excessive digital screen time
10. Long-Term Outcomes
- Symptom persistence: 35–65% into adulthood
- Academic and occupational impact: Higher dropout rates, unemployment risk, reduced earning potential
- Mortality risk: Slightly elevated, linked to accidents and comorbid substance use
11. Summary
ADHD is a common, heritable neurodevelopmental condition marked by dysregulation of attention and impulse control. Diagnosis is based on DSM‑5 criteria, supported by clinical assessment. Evidence-based management involves individualized combinations of behavior therapy and pharmacological treatment. With adequate treatment and support, many individuals achieve significant functional improvements.
