Attention-Deficit Hyperactivity Disorder (ADHD) - Part 1

🧠 Core Features of ADHD

🧠 Developmentally Inappropriate Symptoms

ADHD is characterized by persistent patterns of inattention, hyperactivity, and impulsivity that interfere with functioning or development.

Inattention

Fails to pay close attention to details, makes careless mistakes
Difficulty sustaining attention in tasks or play
Doesn't seem to listen when spoken to directly
Doesn't follow through on instructions, fails to finish tasks
Difficulty organizing tasks and activities
Avoids tasks requiring sustained mental effort
Loses things necessary for tasks
Easily distracted by extraneous stimuli
Forgetful in daily activities

Hyperactivity

Fidgets, squirms in seat
Leaves seat when remaining seated is expected
Runs about or climbs inappropriately (in teens/adults, may be restlessness)
Unable to play quietly
"On the go," "driven by a motor"
Talks excessively

Impulsivity

Blurts out answers before questions completed
Difficulty waiting turn
Interrupts or intrudes on others

Case Example: A 7-year-old boy is brought to his pediatrician because his teacher says he "can't sit still." During the visit, he climbs on the exam table, interrupts constantly, touches everything in the room, and can't seem to listen when spoken to. His mother reports he's always been "on the go," loses his homework daily, forgets his lunch, and acts without thinking—recently running into the street after a ball. At home, simple tasks take forever because he's easily distracted.

📊 Epidemiology

📊 Prevalence and Patterns

Understanding the distribution and characteristics of ADHD across populations.

Prevalence

8-10% of children (US)
5% worldwide
Male predominance: 2-3:1 (boys more likely diagnosed, especially hyperactive type)
Girls underdiagnosed: More likely inattentive presentation

Course and Persistence

50-80% continue to have symptoms into adolescence/adulthood
Increasing diagnosis rates: Better awareness, expanded criteria, or true increase? Debate ongoing
Diagnosis age: Peak diagnosis age 6-12 years
Girls diagnosed later: Average 5 years later than boys

🔬 Etiology and Pathophysiology

🔬 Highly Heritable but Complex

ADHD results from a complex interplay of genetic, neurobiological, and environmental factors.

Genetic Factors

Heritability: 70-80% (strong genetic component)
Multiple genes involved (polygenic)—dopamine and norepinephrine pathways
If one parent has ADHD: 50% chance child affected
If one sibling has ADHD: 30% chance

Neurobiological Factors

Brain differences: Delayed cortical maturation (especially prefrontal cortex—3 years behind)
Altered neurotransmitter function: Dopamine, norepinephrine
Differences in brain structure/connectivity: Smaller prefrontal cortex, basal ganglia

Environmental Risk Factors

Prematurity, low birth weight
Prenatal exposures: Tobacco, alcohol, lead
Maternal stress during pregnancy
Early childhood adversity (trauma, neglect)
Traumatic brain injury

NOT Caused By

Sugar (common myth—no evidence)
Poor parenting (though parenting can exacerbate or help manage)
Too much screen time (may worsen but doesn't cause)
Food additives, preservatives (minimal evidence)

Pathophysiology

Executive Function Deficits: Prefrontal cortex dysfunction → impaired executive functions:

Working memory
Inhibition (impulse control)
Cognitive flexibility
Planning and organization
Emotional regulation

Neurotransmitter Dysregulation: Dopamine and norepinephrine pathways involved (stimulant medications work by enhancing these)

👥 Clinical Presentation

👥 DSM-5 Diagnostic Criteria

Diagnosis requires meeting specific criteria across multiple domains and settings.

DSM-5 Diagnostic Criteria

A. Persistent pattern of inattention and/or hyperactivity-impulsivity interfering with functioning
B. Several symptoms present before age 12
C. Symptoms present in ≥2 settings (home, school, work, with friends)
D. Clear evidence symptoms interfere with functioning
E. Not better explained by another disorder

Symptom Threshold: ≥6 symptoms (≥5 if age 17+) for at least 6 months in either inattention or hyperactivity-impulsivity domains

Combined Presentation (Most Common, 60%)

Meets criteria for both inattention AND hyperactivity-impulsivity
Typical "classic" ADHD

Predominantly Inattentive Presentation (30%)

Meets criteria for inattention but NOT hyperactivity-impulsivity
Formerly called "ADD" (without hyperactivity)
More common in girls
Often underdiagnosed (not disruptive, "daydreamers")

Predominantly Hyperactive-Impulsive Presentation (10%)

Meets criteria for hyperactivity-impulsivity but NOT inattention
More common in younger children (some develop inattention later)

Age-Related Presentation

Preschool (3-5 years): Hyperactivity predominates—constantly moving, can't sit still, climbs excessively, "whirlwind." Diagnosis challenging as normal preschoolers are active.

School-Age (6-12 years): Peak diagnosis age. Academic difficulties emerge, social problems, homework battles. More boys diagnosed (hyperactive/disruptive behaviors noticed).

Adolescence (13-18 years): Hyperactivity decreases (internal restlessness replaces external), inattention persists. Academic struggles worsen, risk-taking behaviors, driving concerns.

🔍 Diagnosis

🔍 Comprehensive Evaluation Required

No single test for ADHD—diagnosis is clinical, based on comprehensive assessment across multiple domains.

Clinical Interview — Detailed developmental and medical history, symptom onset, duration, settings, functional impairment, family history

Rating Scales/Questionnaires — Parent and teacher reports essential (need symptoms in ≥2 settings). Standardized scales: Vanderbilt Assessment Scales, Conners Rating Scales, ADHD Rating Scale-5

School Information — Report cards, teacher observations, testing accommodations, interventions tried

Direct Observation — Behavior during office visit (limited value—many behave well in novel, structured settings)

Rule Out Other Conditions — Hearing and vision screening, consider learning disabilities, intellectual disability, autism, anxiety, mood disorders, sleep disorders, medical conditions

Medical Evaluation — Physical exam, growth parameters, consider lead screening, thyroid testing, sleep study if indicated

Psychoeducational Testing — IQ testing, achievement testing, executive function testing

Diagnostic Challenges: ADHD is both overdiagnosed AND underdiagnosed. Overdiagnosis: Normal active behavior misidentified, pressure for medication. Underdiagnosis: Inattentive presentation (especially girls), adults, comorbid conditions masking ADHD.

Differential Diagnosis

Normal developmental variation (active preschooler, bored gifted child)
Learning disabilities (inattention secondary to frustration)
Anxiety disorders (inattention from worry, restlessness from anxiety)
Depression (poor concentration, psychomotor agitation)
Sleep disorders (sleep apnea, insufficient sleep—cause inattention, hyperactivity)
Autism spectrum disorder (social inattention, repetitive behaviors)
Oppositional defiant disorder (won't vs. can't follow instructions)
Bipolar disorder (controversial—symptoms overlap but episodic vs. chronic)
Trauma/PTSD (hypervigilance, emotional dysregulation)
Medical conditions: Anemia, thyroid disorders, seizures (absence—staring spells)
Substance use (adolescents)

Important: Many conditions co-occur with ADHD (not "either/or" but "both/and")

🔑 High-Yield ADHD Summary - Part 1

Domain	Key Points	Clinical Implications
Core Features	Inattention, hyperactivity, impulsivity	Must be developmentally inappropriate and cause impairment
Epidemiology	8-10% prevalence, male predominance 2-3:1	Girls underdiagnosed (inattentive type)
Etiology	70-80% heritable, prefrontal cortex dysfunction	Not caused by sugar, parenting, or screen time
Presentations	Combined (60%), inattentive (30%), hyperactive-impulsive (10%)	Inattentive type often missed, especially in girls
Diagnosis	Clinical, requires symptoms in ≥2 settings	Teacher input essential, rule out other conditions

🎯 Key Takeaways - Part 1

ADHD is the most common neurodevelopmental disorder of childhood, affecting 8-10% of children
Characterized by developmentally inappropriate inattention, hyperactivity, and impulsivity
Highly heritable (70-80%) with strong genetic component and neurobiological basis
NOT caused by sugar, poor parenting, or too much screen time
Three presentations: combined (most common), predominantly inattentive, predominantly hyperactive-impulsive
Diagnosis requires comprehensive evaluation including parent/teacher rating scales and school information
Symptoms must be present in ≥2 settings and cause functional impairment
Differential diagnosis important—many conditions mimic or co-occur with ADHD

🌟 Understanding the ADHD Brain

ADHD represents a neurodevelopmental difference in brain structure and function, particularly affecting the prefrontal cortex and its connections. This results in challenges with executive functions—the cognitive processes that help us plan, focus attention, remember instructions, and juggle multiple tasks successfully.

Rather than a deficit of attention, ADHD often involves difficulty regulating attention—being easily distracted by irrelevant stimuli while struggling to focus on relevant ones. The hyperactivity and impulsivity components reflect challenges with behavioral inhibition and self-regulation.

Clinical Insight: "ADHD isn't a deficit of attention, but an dysregulation of attention—difficulty directing attention where it needs to go, when it needs to be there."

🧠 Attention-Deficit Hyperactivity Disorder (ADHD) - Part 1