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Attention deficit hyperactivity disorder

Background knowledge 🧠

Definition

  • Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by persistent patterns of inattention and/or hyperactivity-impulsivity that interfere with functioning or development.
  • Symptoms typically present before the age of 12.
  • It affects cognitive, academic, behavioural, emotional, and social functioning.

Epidemiology

  • ADHD is one of the most common neurodevelopmental disorders in children, affecting approximately 5-7% of school-aged children.
  • More common in males than females, with a ratio of about 2:1.
  • Symptoms may persist into adulthood in about 50-60% of cases.
  • Prevalence in adults is estimated to be around 2-5%.

Aetiology and Pathophysiology

  • Exact cause unknown; believed to be multifactorial.
  • Genetic factors play a significant role; heritability is estimated at 70-80%.
  • Environmental factors: prenatal exposure to tobacco, alcohol, and drugs; low birth weight; and psychosocial adversity.
  • Neurobiological abnormalities: reduced dopaminergic and noradrenergic activity in the prefrontal cortex and basal ganglia.
  • Brain imaging studies show differences in brain structure, particularly in the frontal lobe, basal ganglia, and cerebellum.

Types

  • Predominantly Inattentive Presentation: Difficulty sustaining attention, forgetfulness, disorganization.
  • Predominantly Hyperactive-Impulsive Presentation: Hyperactivity, fidgeting, impulsivity.
  • Combined Presentation: Both inattentive and hyperactive-impulsive symptoms.
  • The presentation may change over time.

Clinical Features 🌑️

Symptoms

  • Inattention: Difficulty sustaining attention, careless mistakes, difficulty organizing tasks, easily distracted.
  • Hyperactivity: Fidgeting, inability to stay seated, excessive talking, running/climbing in inappropriate situations.
  • Impulsivity: Blurting out answers, difficulty waiting turn, interrupting others.
  • Symptoms must be present in two or more settings (e.g., home, school, work).

Signs

  • Restlessness and an inability to sit still.
  • Inappropriate running or climbing.
  • Difficulty engaging in quiet activities.
  • Difficulty with following instructions or completing tasks.
  • Disruptive behaviour in social settings.

Investigations πŸ§ͺ

Tests

  • ADHD is a clinical diagnosis based on history and observation.
  • Use of standardized diagnostic tools, such as the Conners’ Rating Scales, ADHD Rating Scale IV, and SNAP-IV.
  • Assessment of comorbid conditions (e.g., learning disabilities, mood disorders).
  • Consider neuropsychological testing in complex cases.
  • Rule out other conditions that may mimic ADHD (e.g., anxiety, depression).

Management πŸ₯Ό

Management

  • Multimodal approach: Behavioural therapy, educational interventions, and pharmacotherapy.
  • First-line pharmacotherapy: Stimulants (e.g., methylphenidate, dexamfetamine).
  • Non-stimulant options: Atomoxetine, guanfacine, clonidine.
  • Behavioural interventions: Parent training programmes, school-based interventions.
  • Monitoring for side effects of medication: growth retardation, sleep disturbances, cardiovascular effects.
  • Regular follow-up to assess treatment efficacy and adherence.

Complications

  • Increased risk of comorbid psychiatric disorders: anxiety, depression, oppositional defiant disorder.
  • Educational underachievement and school failure.
  • Increased risk of substance misuse.
  • Interpersonal relationship difficulties.
  • Occupational and social impairments in adulthood.

Prognosis

  • Symptoms may persist into adolescence and adulthood.
  • Approximately 30-50% of individuals diagnosed in childhood continue to meet the diagnostic criteria in adulthood.
  • Some may experience a reduction in hyperactive and impulsive symptoms over time, while inattentive symptoms may persist.
  • Early intervention and treatment improve long-term outcomes.
  • Ongoing management is often necessary.

Key Points

  • ADHD is a common, chronic neurodevelopmental disorder.
  • It significantly impacts social, academic, and occupational functioning.
  • Diagnosis is clinical, supported by standardized tools.
  • Management includes behavioural therapy and pharmacotherapy.
  • Early diagnosis and treatment improve outcomes.

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