Autism spectrum disorder

Overview

•Lifelong neurodevelopmental condition - qualitative impairments in social communication/interaction + restricted, repetitive behaviours

•Prevalence ~1% in UK; male:female ratio ~3-4:1 - females frequently underdiagnosed due to camouflaging/masking

•~50% of people with ASD also have a learning disability; ADHD co-occurs in 50-70%

🎯

The MMR vaccine does NOT cause autism. This originated from a fraudulent, retracted 1998 paper. A common exam distractor.

Presentation

•Social communication deficits

•Reduced eye contact - often earliest sign noted by parents

•Delayed social smile, failure to point/share joint attention

•Language delay or regression; echolalic/scripted speech

•Difficulty reading non-verbal cues; impaired pretend play

•Restricted, repetitive behaviours

•Stereotyped repetitive movements ('stimming') - hand-flapping, rocking, spinning

•Insistence on sameness; distress when routines change

•Highly restricted, fixated interests

•Sensory hyper- or hypo-reactivity (light, sound, texture, pain)

💡

Camouflaging (mimicking neurotypical social behaviour) is far more common in females and higher-functioning individuals - leads to diagnostic delays of years/decades and is associated with higher rates of burnout, anxiety, and depression.

Investigations

•No biological test or biomarker - diagnosis is made clinically via specialist MDT assessment

🥇 First-line

•referral to specialist MDT + detailed developmental history from parents/carers + cognitive/intellectual assessment + hearing and vision assessment

🏆 Gold standard

•ADOS-2 (Autism Diagnostic Observation Schedule, 2nd edition) - standardised observational assessment; ADI-R (Autism Diagnostic Interview - Revised) - structured caregiver interview

🥈 Second-line

•genetic testing (chromosomal microarray, Fragile X) if genetic syndrome suspected; EEG only if epilepsy clinically suspected

Differential diagnosis

Key differentials vs ASD

Condition	Distinguishing feature
ADHD	Inattention/impulsivity; lacks restricted interests/insistence on sameness - frequently co-occurs with ASD
Social (pragmatic) communication disorder	Social communication impairment WITHOUT restricted/repetitive behaviours - key distinction
OCD	Rituals are ego-dystonic and distressing; ASD restricted interests are pleasurable/self-soothing
Anxiety disorder	Repetitive behaviours/social withdrawal secondary; retains social connectedness; prior period of normal function
Schizophrenia	Social withdrawal secondary to hallucinations/delusions - not a primary neurodevelopmental trait

Management

•ASD cannot be cured - management aims to maximise quality of life and support development; early intensive intervention improves long-term outcomes

🥇 First-line

•structured behavioural/educational intervention (as early as possible); speech and language therapy (including AAC for non-verbal individuals); psychoeducation and parent/carer support; social skills training

🥈 Second-line

•pharmacological treatment of co-occurring conditions only - methylphenidate / lisdexamfetamine (ADHD); SSRIs (anxiety); melatonin (sleep); adapted CBT for anxiety/depression

⚠️

There is NO pharmacological treatment licensed for the core features of ASD in the UK. Medication targets co-occurring conditions only. Always screen for co-occurring ADHD (present in 50-70%) - it is frequently missed.

Complications

Co-occurring conditions

ADHD - 50-70%

Learning disability - ~50%

Epilepsy - up to 30% (higher with intellectual disability)

Anxiety disorders - very common; often presenting complaint in adults

Depression and OCD

Self-harm/suicidal ideation - significantly elevated, especially females diagnosed late

Sleep disorders - common across all ages

Social isolation, unemployment, educational underachievement

⚠️

Diagnostic overshadowing - attributing all symptoms to the autism diagnosis risks missing treatable co-occurring conditions such as ADHD, anxiety, and depression.