Attention-Deficit/ Hyperactivity Disorder (ADHD)

Written by: Khalil Abualhumos, M.D.

Keywords: ADHD, attention deficit, hyperactivity, impulsivity, Attention Deficit Hyperactivity Disorder, inattention, neuropsychiatric disorder, dopamine dysfunction, DSM-5 criteria, ICD-10 criteria, methylphenidate, behavioral therapy, cognitive behavioral therapy, executive function deficit, academic impairment.

Overview

Attention-Deficit/Hyperactivity Disorder (ADHD) is a neuropsychiatric condition characterized by inattention, hyperactivity, and impulsivity, affecting ~5% of children/adolescents and ~2.5% of adults, with a higher prevalence in boys. It has a strong genetic component (~75% heritability) and is linked to dopamine dysfunction, neuroanatomical abnormalities, and psychosocial factors. ADHD presents in three types: inattentive, hyperactive-impulsive, and combined. Symptoms often emerge by age 3 and persist into adulthood, impacting academic, social, and emotional development. Diagnosis requires persistent symptoms in multiple settings per DSM-5/ICD-10 criteria. Management includes stimulant medications (e.g., methylphenidate), non-stimulants (e.g., atomoxetine), and behavioral therapy. The best outcomes result from combined pharmacologic and psychosocial interventions. While hyperactivity may resolve, inattention and impulsivity often persist, increasing risks of learning disabilities, mood disorders, and substance abuse. Long-term prognosis varies, with symptoms persisting into adulthood in ~60% of cases, particularly in those with comorbid conditions.

Buzzwords Scenario: A 7-year-old boy presents with inattention, fidgeting, and impulsivity at school and home. He struggles with assignments, frequently interrupts, and leaves his seat. His father had similar symptoms. Exam shows no neurological deficits, but he is restless and has difficulty maintaining attention.

Definition

Attention-deficit/ hyperactivity disorder (ADHD) is a neuropsychiatric condition affecting all age groups, characterized by diminished attention, impulsivity, and hyperactivity.

Epidemiology

●     Incidence: 7–8% of prepubertal elementary school children.

●     Prevalence: ~5% in children/ adolescents and ~2.5% in adults.

●     Gender: Boys > girls (2:1 to 9:1).

Etiology

●     Genetic factors:

○     ADHD is highly genetic (~75% heritability).

○     Higher risk in siblings and parents of ADHD children.

■     Parents and siblings of children with ADHD have a 2–8 times higher risk than the general population.

○     Dopamine-related genes (DAT1, DRD4) are linked to ADHD.

●     Neurochemical factors: Dopamine and norepinephrine play key roles.

○     ADHD may be due to abnormal arousal levels and emotional regulation issues.

●     Neurophysiologic & neuroanatomical factors:

○     EEG findings: Increased theta and beta activity in the frontal region.

○     Brain imaging: Smaller and less active prefrontal cortex, thalamus, and cerebellum.

●     Developmental factors: Prematurity, maternal infections, and birth complications may contribute.

●     Psychosocial factors: Severe abuse, neglect, and chronic stress can cause ADHD-like symptoms.

●     High-risk groups:

○     Siblings of children with ADHD are more likely to develop ADHD, psychiatric disorders, learning difficulties, and academic struggles.

○     Parents of children with ADHD have a higher incidence of substance use disorders.

Types

●     Predominantly inattentive type: More focus issues, fewer hyperactivity symptoms.

●     Predominantly hyperactive-impulsive type: More hyperactivity and impulsivity.

●     Combined type: Both inattention and hyperactivity/impulsivity.

○     More stable diagnosis over time and is linked to conduct disorders.

NOTE: Children with hyperactive-impulsive ADHD are diagnosed earlier than those with inattentive symptoms.

Clinical Features

●     Onset: Symptoms often appear by age 3, but diagnosis is usually made in kindergarten or elementary school when teachers compare behavior with peers.

●     Early signs (Infancy & toddler age):

○       Rarely diagnosed in infancy.

○     Some infants may be very active in the crib, sleep less, and cry a lot.

●     School-related symptoms:

○     Rushing through tasks (e.g., answering only the first few questions on a test).

○     Difficulty waiting their turn (e.g., answering before called on).

○     Struggles with delayed gratification (e.g., cannot wait even a minute at home).

●     Key ADHD characteristics (Most to least common):

○     Hyperactivity (constant movement, fidgeting) - Most common.

○     Attention deficit (short attention span, distractibility, trouble finishing tasks).

○     Impulsivity (acting without thinking, abrupt activity shifts, poor organization).

○     Memory & thinking deficits (difficulty retaining information).

○     Learning disabilities (struggles with reading, writing, or math).

○     Speech & hearing deficits.

●     Additional features:

○     Motor skill issues (poor coordination, clumsiness).

○     Emotional instability (mood swings, frustration).

○     Aggression & defiance (behavioral issues).

○     School difficulties (academic & behavioral struggles).

○     Comorbid disorders (communication or learning difficulties affecting knowledge retention and performance).

●     Impact:

○     Academic, social, and interpersonal difficulties.

○     Often occurs with learning disorders, anxiety, mood disorders, and disruptive behavior disorders.

●     Progression:

○     Hyperactivity is usually the first symptom to resolve.

○     Distractibility and impulse-control issues are the last to persist.

Diagnosis

Diagnosis is based on detailed history and direct observation in different settings.

●     Symptoms must be persistent, impairing, and present in at least two settings (e.g., school & home).

Assessment:

●     History: Prenatal, perinatal, toddler history, family history of ADHD or related conditions.

●     School history & teacher reports: Essential for assessing learning difficulties.

●     Mental status exam: Distractibility, impulsivity, emotional instability, but no thought disorder.

●     Neurologic exam: May show subtle coordination, perceptual, or motor issues.

●     Rule out other conditions:

○     Medical causes: Seizures, hearing/vision problems, thyroid issues, hypoglycemia.

○     Psychiatric causes: Anxiety, depression, social rejection, self-esteem issues.

●     EEG: If seizures (e.g., absence seizures) are suspected.

●     ECG & cardiac evaluation if there are risk factors before treatment.

●     Continuous performance task (computerized attention test) may help monitor treatment response.

Diagnosis requirements (DSM-5 & ICD-10):

●     Must cause functional impairment in daily life.

●     Must not be due to another mental disorder.

DSM-5 vs. ICD-10 diagnostic criteria:

●     Duration: ≥6 months.

●     Onset: Before age 12 (DSM-5) or before age 5 (ICD-10).

●     Symptoms required:

○     ≥6 symptoms in either inattention or hyperactivity/impulsivity (≥5 for age 17+).

○     Inattention (e.g., poor focus, distractibility, forgetfulness).

○     Hyperactivity/impulsivity (e.g., fidgeting, interrupting, excessive talking).

○     Must cause functional impairment in daily life.

○     Must not be due to another mental disorder.

●     Severity levels:

○     Mild: Minimal symptoms, mild impairment.

○     Moderate: Intermediate symptoms and impairment between mild and severe.

○     Severe: Many symptoms, significant impairment.

Management

Pharmacotherapy (First-line treatment):

●     CNS stimulants: Most effective treatment for ADHD with generally mild side effects.

○       Methylphenidate (e.g., Ritalin, Concerta)

■       May worsen motor tics in some children.

○     Amphetamine preparations: Often used as a second option if methylphenidate fails.

ALERT: Avoid in children/ adults with known cardiac risks.

●       Nonstimulant medications:

○       Atomoxetine (Strattera)

■       A norepinephrine uptake inhibitor approved for children ≥6 years.

■       Carries a black-box warning for increased suicidal thoughts/ behaviors; monitor closely.

○       α-Agonists (Clonidine & Guanfacine)

■       Guanfacine is particularly useful for children with comorbid tic disorders when stimulants exacerbate tics.

ALERT: Atomoxetine (Strattera) carries a black-box warning for increased suicidal thoughts/ behaviors; monitor closely.

Monitoring pharmacologic treatment:

●     Before initiation: Conduct a thorough physical exam; measure blood pressure, pulse, weight, height; obtain LFT (liver function test), KFT (kidney function test), and ECG if there is a family history or cardiac risk.

●     During treatment: Regularly monitor growth, vital signs, and academic/ behavioral changes, ensure annual check-ups, and educate children on medication use and side effects.

Psychosocial interventions:

●       Key components:

○       Psychoeducation, academic organization skills training, behavior modification, and social skills training.

○       Parent training to develop effective behavioral interventions and positive reinforcement strategies.

○     Cognitive behavioral therapy (CBT) and group therapy to improve social skills and self-esteem.

Multimodal treatment study of children with ADHD (MTA study):

●       Findings:

○       All treatment groups showed improvement.

○     Best results: Combination treatment (medication + behavior therapy).

○     Most benefit in ADHD children with comorbid oppositional, anxiety, or mood disorders.

●       Overall implication:

○     Medication + psychosocial therapy = best overall outcome.

○       Especially beneficial for children with comorbid learning, anxiety, mood, or behavioral disorders.

Prognosis

●      5–8% of school-age children.

○      60–85% of affected children continue to have symptoms in adolescence.

○     Up to 60% remain symptomatic into adulthood.

●       Factors affecting persistence:

○       Family history of ADHD.

○       Adverse life events.

○       Comorbid conduct disorder, depression, or anxiety.

●       Long-term outcomes:

○     Partial remission is common, with risks of:

■       Antisocial behavior.

■       Substance use disorders (especially with conduct disorder).

■       Mood disorders.

○     Learning difficulties may persist throughout life.

Reference

Boland, R., Verduin, M. L., & Ruiz, P. (Eds.). (2022). Attention-deficit/hyperactivity disorder. In Kaplan & Sadock's synopsis of psychiatry (12th ed., Chapter 2.4). Wolters Kluwer.