Key Facts

ASD is a lifelong neurodevelopmental condition with wide variation in presentation and functioning. The shift from categorical (Asperger's, autism) to a spectrum model reflects the heterogeneity of the condition.

Epidemiology

Prevalence ~1-2% of the population (~700,000 in the UK). M:F ~3:1 (increasing recognition that many women are undiagnosed due to 'masking'). Diagnosis increasingly made in adulthood. Strong genetic component.

Aetiology

• Genetic: Heritability ~80-90%; hundreds of genes implicated; monozygotic twin concordance ~60-90%
• Neurobiological: Altered connectivity (particularly long-range connections), differences in mirror neurone system, amygdala, and fusiform face area
• Environmental: Advanced paternal age, prenatal infections, valproate exposure (MHRA warning)
• NOT caused by: MMR vaccine (thoroughly debunked — Wakefield study retracted)

Pathophysiology

• Altered neural connectivity: Local over-connectivity with reduced long-range connectivity
• Theory of mind deficits: Difficulty understanding others' mental states (but not absent in all)
• Weak central coherence: Tendency to focus on details rather than global picture
• Executive function difficulties: Planning, flexibility, working memory
• Sensory processing differences: Hyper- or hypo-sensitivity to sensory stimuli

Social Communication and Interaction

• Difficulty with reciprocal conversation and non-verbal communication (eye contact, gestures, facial expressions)
• Challenges in developing, maintaining, and understanding relationships
• Difficulty with social-emotional reciprocity (sharing emotions, turn-taking)
• Literal interpretation of language, difficulty with sarcasm, idioms, humour

Restricted, Repetitive Behaviours and Interests

• Stereotyped motor movements (hand flapping, rocking)
• Insistence on sameness, inflexible adherence to routines
• Highly focused, intense interests
• Sensory hyper- or hypo-reactivity (e.g., distress at certain sounds, fascination with lights)

Presentation Across the Lifespan

• Children: May present with language delay, play differences, social difficulties, behavioural challenges
• Adults: May present seeking diagnosis after recognising traits, often after child's diagnosis; social difficulties, anxiety, employment challenges
• Women: Often 'camouflage' — consciously mask difficulties; diagnosis frequently delayed

Red Flags for Assessment Referral

• Regression of language or social skills (especially age 18-24 months)
• Absence of pointing/joint attention by 14 months
• No single words by 16 months or 2-word phrases by 24 months
• Social difficulties across settings (not explained by anxiety alone)

Bedside

• ADOS-2: Gold standard observation-based assessment of social communication and behaviour
• ADI-R: Semi-structured parent interview covering developmental history
• Developmental history: Milestones, early social behaviours, school reports
• AQ-10/AQ-50: Screening tools (Autism Quotient)

Bloods

• Not routinely required for diagnosis
• Genetic testing (chromosomal microarray): If dysmorphic features or intellectual disability
• Fragile X testing: If intellectual disability present
• Lead levels, metabolic screen: If developmental regression

Special Tests

• Cognitive assessment (WAIS/WISC): Assess intellectual functioning
• Hearing test: Exclude hearing loss in children with language delay
• Sensory profile assessment: Occupational therapy
• EEG: If epilepsy suspected (~20-30% comorbidity)

Non-pharmacological (NICE CG128/CG142)

• Psychoeducation: Understanding ASD for individual and family
• Environmental modifications: Sensory-friendly environments, visual schedules, structured routines
• Social skills programmes: For children and young people
• Speech and language therapy: Pragmatic communication support
• Occupational therapy: Sensory processing, daily living skills
• Behavioural support: PBS (Positive Behaviour Support) for challenging behaviour — NOT ABA in isolation
• CBT (adapted): For comorbid anxiety and depression
• Education: EHCP (Education, Health and Care Plan) for support in school

Pharmacological

• No medication for core ASD features
• Treat comorbidities:
  • Anxiety: SSRIs (start low, go slow — increased sensitivity)
  • ADHD: Methylphenidate or atomoxetine (may be less well-tolerated)
  • Sleep disturbance: Melatonin 2-5mg ON (commonly used, evidence-based)
  • Aggression/irritability: Risperidone 0.25-2mg (short-term, specialist only — significant metabolic side effects)
• Avoid polypharmacy

Referral Criteria

• Suspected ASD — specialist neurodevelopmental assessment service
• Children: Community paediatrics or CAMHS
• Adults: Adult ASD assessment service
• Complex needs: MDT including SALT, OT, psychology, psychiatry

• Lifelong condition: ASD is not a disease to be 'cured' — focus on support, adaptation, and quality of life
• Variable outcome: Some live independently, work, and have relationships; others require lifelong support
• Good prognostic factors: Average/above-average IQ, early intervention, language development, supportive environment
• Comorbidities significantly affect quality of life: Anxiety, depression, epilepsy, sleep disorders
• Life expectancy: Reduced by ~16-30 years compared to general population (largely driven by those with intellectual disability, epilepsy, and accidents)
• Employment: Only ~22% of autistic adults in the UK are in any kind of employment

DSM-5 Severity Levels

Autism vs ADHD Comparison