Key Facts

ADHD is one of the most common neurodevelopmental disorders. It persists into adulthood in approximately 65% of cases. Early diagnosis and management significantly improve functional outcomes.

Epidemiology

Prevalence ~3-5% in children, ~2-3% in adults. M:F 3:1 in children (diagnosis increasingly recognised in women). Often coexists with ASD, learning disabilities, anxiety, depression, and conduct disorder.

Aetiology

• Genetic: Heritability ~75-80% (one of the most heritable psychiatric conditions); polygenic — multiple genes of small effect (DAT1, DRD4, DRD5)
• Neurobiological: Prefrontal cortex hypofunction, dopaminergic and noradrenergic deficiency
• Environmental: Prematurity, low birth weight, prenatal tobacco/alcohol exposure, lead exposure
• NOT caused by: Poor parenting, sugar, food additives (though diet may modestly affect symptoms)

Pathophysiology

• Prefrontal cortex dysfunction: Executive function deficits — working memory, planning, impulse control, sustained attention
• Dopamine/noradrenaline deficiency: In prefrontal-striatal circuits; basis for stimulant medication
• Reward pathway alteration: Preference for immediate over delayed rewards (delay aversion)
• Default mode network (DMN): Failure to suppress DMN during tasks → mind-wandering

Inattentive Symptoms (≥6 of 9 in children; ≥5 in adults ≥17)

• Fails to attend to details, careless mistakes
• Difficulty sustaining attention
• Does not seem to listen when spoken to
• Fails to follow through on instructions/finish tasks
• Difficulty organising tasks
• Avoids tasks requiring sustained mental effort
• Loses things necessary for tasks
• Easily distracted
• Forgetful in daily activities

Hyperactive-Impulsive Symptoms (≥6/5)

• Fidgets, squirms
• Leaves seat when remaining seated expected
• Runs/climbs inappropriately (restlessness in adults)
• Unable to engage in activities quietly
• 'On the go' or 'driven by a motor'
• Talks excessively
• Blurts out answers
• Difficulty waiting turn
• Interrupts or intrudes on others

Red Flags

• Academic failure or work underperformance — screen for ADHD
• Substance misuse (self-medication) — common comorbidity
• Traffic accidents — impulsivity and inattention increase risk
• Emotional dysregulation — frequently misdiagnosed as personality disorder or bipolar disorder

Bedside

• DIVA 5.0 (Diagnostic Interview for ADHD in Adults): Structured diagnostic interview
• Conners' Rating Scales: Parent, teacher, and self-report versions
• QB Test: Computerised continuous performance test with motion tracking (NICE-endorsed)
• Developmental history: Symptoms before age 12, multiple settings

Bloods

• TFTs: Exclude hyperthyroidism
• FBC, U&Es, LFTs: Baseline before medication

Special Tests

• Cardiovascular assessment: HR, BP — baseline and after each dose change
• ECG: If family history of cardiac disease or structural heart defects
• Height and weight: Monitor in children on stimulants (growth suppression)

Non-pharmacological

• Psychoeducation: Understanding ADHD, environmental strategies
• Behavioural strategies: Structured routines, organisational aids, timers, checklists
• Parent training programmes: First-line for pre-school children (NICE NG87)
• CBT: For adults with ADHD — addresses executive function and emotional dysregulation
• Workplace/educational adjustments: Extra time in exams, reduced distractions

Pharmacological (NICE NG87)

Children ≥5 and young people:

• First-line: Methylphenidate (Medikinet XL 10-60mg OD or Concerta XL 18-54mg OD)
• Second-line: Lisdexamfetamine (Elvanse) 20-70mg OD
• Third-line: Dexamfetamine, atomoxetine (non-stimulant), guanfacine (non-stimulant)

Adults:

• First-line: Lisdexamfetamine (Elvanse) 30-70mg OD or methylphenidate
• Second-line: Dexamfetamine, atomoxetine

Monitoring:

• HR, BP at baseline, after each dose change, then 6-monthly
• Height and weight every 6 months in children
• Annual cardiovascular and growth review

Referral Criteria

• Suspected ADHD — specialist ADHD/neurodevelopmental service (diagnosis must be by specialist)
• Children: Paediatrician or CAMHS
• Adults: Adult ADHD service
• Comorbid conditions — MDT approach

• Persistence: ~65% of children with ADHD continue to meet criteria in adulthood
• Medication: Stimulants effective in ~70-80% (NNT ~3); improve attention, reduce hyperactivity-impulsivity
• Without treatment: Increased risk of academic failure, unemployment, substance misuse, accidents, criminal behaviour
• With treatment: Functional outcomes significantly improved; reduced accident and substance misuse risk
• Growth: Stimulants may reduce height by ~1-2cm in childhood (effect diminishes and may catch up)
• Substance misuse: Paradoxically, treating ADHD with stimulants reduces later substance misuse risk

ADHD Medication Comparison