Autism Spectrum Disorder (ASD)

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

Definition

Autism Spectrum Disorder (ASD) is a neurodevelopmental condition characterised by persistent deficits in social communication and interaction, alongside restricted, repetitive behaviours, interests, or activities.

Aetiology

• Genetic factors: strong hereditary component, multiple genetic variations identified.
• Neurobiological factors: abnormal brain connectivity and neurotransmitter imbalances.
• Environmental factors: prenatal exposure to toxins, maternal infections, low birth weight.

Pathophysiology

• Altered neural connectivity affecting social cognition and executive function.
• Abnormal serotonin and dopamine signalling contributing to repetitive behaviours.
• Amygdala and prefrontal cortex dysfunction affecting social interactions and emotional processing.

Risk factors

• Family history of ASD or other neurodevelopmental disorders.
• Male sex (ASD is more common in boys).
• Premature birth and low birth weight.
• Advanced parental age.
• Prenatal exposure to infections or environmental toxins.

Signs and symptoms

• Social communication deficits:
  • Difficulty understanding social cues and emotions.
  • Limited use of eye contact, gestures, or facial expressions.
  • Delayed or absent speech development.
• Repetitive behaviours and restricted interests:
  • Repetitive movements (e.g., hand-flapping, rocking).
  • Insistence on routines and resistance to change.
  • Highly focused interests (e.g., numbers, trains, certain topics).
• Other associated features:
  • Unusual sensory responses (e.g., sensitivity to light, sound, textures).
  • Difficulty with motor coordination.
  • Emotional regulation difficulties.

Investigations

• Developmental history: comprehensive history from parents and caregivers.
• Autism-specific screening tools: Modified Checklist for Autism in Toddlers (M-CHAT), Social Communication Questionnaire (SCQ).
• Formal diagnostic assessment: Autism Diagnostic Observation Schedule (ADOS-2) and Autism Diagnostic Interview-Revised (ADI-R).
• Hearing and vision tests: to rule out sensory impairments.
• Genetic testing: if syndromic ASD suspected (e.g., Fragile X syndrome).

Management

1. Early intervention and behavioural therapies:

• Applied Behaviour Analysis (ABA) to improve communication and social skills.
• Speech and language therapy for communication difficulties.
• Occupational therapy for sensory and motor challenges.

2. Educational support:

• Individualised Education Plan (IEP) or Education, Health and Care Plan (EHCP).
• Specialist autism-friendly schools or additional classroom support.

3. Pharmacological management (if required for comorbidities):

• Melatonin for sleep disturbances.
• SSRIs for anxiety or obsessive-compulsive behaviours.
• Atypical antipsychotics (e.g., risperidone, aripiprazole) for severe aggression or self-injury.

4. Support for families and caregivers:

• Parent training programmes (e.g., EarlyBird Programme).
• Access to social care and respite services.
• Peer support groups for families.

5. Referral:

• Paediatrician or child psychiatrist: for diagnostic confirmation and specialist input.
• Speech and language therapist: for communication interventions.
• Educational psychologist: for school-based support planning.

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