Attention Deficit Hyperactivity Disorder (ADHD)

Definition | Aetiology | Pathophysiology | Risk factors | Signs and symptoms | Investigations | Management

Definition

Attention Deficit Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder characterised by persistent patterns of inattention, hyperactivity, and impulsivity that interfere with daily functioning and development.

Aetiology

• Genetic factors: strong hereditary component, multiple risk-associated genes identified.
• Neurobiological factors: dysregulation of dopamine and noradrenaline pathways in the prefrontal cortex.
• Environmental factors: prenatal exposure to alcohol, smoking, premature birth, low birth weight.

Pathophysiology

• Reduced dopamine and noradrenaline activity in the prefrontal cortex, affecting attention regulation and impulse control.
• Delayed cortical maturation, particularly in frontal regions responsible for executive function.
• Increased connectivity in default mode network leading to distractibility.

Risk factors

• Family history of ADHD or other neurodevelopmental disorders.
• Male sex (higher prevalence in boys).
• Exposure to prenatal toxins (e.g., maternal smoking, alcohol use).
• Prematurity and low birth weight.
• Psychosocial adversity (e.g., neglect, trauma, family conflict).

Signs and symptoms

• Inattention:
  • Difficulty sustaining attention on tasks.
  • Careless mistakes in schoolwork or work-related tasks.
  • Easily distracted by extraneous stimuli.
  • Forgetfulness and poor organisation.
• Hyperactivity:
  • Excessive fidgeting or restlessness.
  • Difficulty remaining seated when expected.
  • Excessive talking and difficulty engaging in quiet activities.
• Impulsivity:
  • Interrupting conversations or blurting out answers.
  • Difficulty waiting for turns.
  • Acting without considering consequences.

Investigations

• Clinical assessment: comprehensive history and collateral information from parents, teachers, and caregivers.
• Formal diagnostic assessment: ADHD-specific interviews (e.g., Diagnostic Interview for ADHD in Adults [DIVA] or Child Interview for ADHD).
• Neuropsychological testing: to assess executive function and working memory.
• Exclusion of other conditions: blood tests (FBC, TFTs) if other medical causes suspected.

Management

1. Behavioural and educational interventions:

• Parent training programmes (e.g., Incredible Years, Triple P).
• Classroom modifications (e.g., structured routines, seating arrangements, minimal distractions).
• Social skills training and executive function coaching.

2. Pharmacological management:

• First-line: Stimulants (e.g., methylphenidate, lisdexamfetamine).
• Second-line: Non-stimulants (e.g., atomoxetine, guanfacine) if stimulants are contraindicated or not tolerated.
• Regular monitoring for side effects (e.g., growth suppression, appetite loss, sleep disturbances).

3. Psychological support:

• Cognitive behavioural therapy (CBT) for emotional regulation and impulse control.
• Mindfulness and relaxation techniques to manage hyperactivity.

4. Support for families and caregivers:

• Access to support groups and parenting workshops.
• Guidance on managing behaviour at home and school.
• Social care referrals if additional support is needed.

5. Referral:

• Paediatrician or child psychiatrist: for diagnosis and medication initiation.
• Educational psychologist: for school-based interventions and support.
• CAMHS or adult ADHD services: for ongoing management.

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