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Autism Spectrum Disorder

Neurodevelopmental disorder with persistent social communication deficits and restricted/repetitive behaviors beginning in early development and causing functional impairment

Review date
reviewed 2026-05-04
Reading time
8 min read
Author
Dr Kola Tytler MBBS CertHE MBA MSt MRCGP
Psychiatry & Behavioral Sciencecommonlong-term-condition
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Condition details
Psychiatry & Behavioral Science
common
8 min read
reviewed 2026-05-04
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About This Page

This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.

Key points

  • ASD requires both social communication/interaction deficits and restricted/repetitive behaviors from early development
  • Diagnosis is clinical; ADOS-2 may support assessment
  • Screen toddlers with M-CHAT-R/F; parental concern warrants evaluation
  • Early intervention, speech/language, OT, educational supports, and behaviorally informed interventions are core
  • Risperidone/aripiprazole treat severe irritability/aggression, not core social communication deficits

Overview

ASD is defined by social-emotional reciprocity deficits, nonverbal communication deficits, relationship difficulties, and restricted/repetitive behaviors or sensory differences. Symptoms begin early but may become more apparent as social demands rise.

Epidemiology

ASD prevalence has risen due to recognition, screening, and diagnostic changes. Co-occurring ADHD, intellectual disability, language disorder, epilepsy, sleep problems, anxiety, GI symptoms, feeding selectivity, and sensory differences are common.

Clinical Features

Symptoms
Limited social reciprocity or response to name
Reduced eye contact, gestures, facial expression, integrated communication
Difficulty relationships or imaginative peer play
Stereotypies, echolalia, sameness, circumscribed interests, sensory hyper/hyporeactivity
Regression, seizures, self-injury, severe aggression, catatonia, failure to thrive
Signs
Reduced joint attention, atypical eye contact, repetitive movements, echolalia
Sensory distress with sounds/textures/lights/transitions
Macrocephaly, dysmorphism, neurocutaneous signs, focal findings suggest genetic/neuro condition
Self-injury, aggression, elopement risk

Investigations

First-line
Developmental/DSM-5-TR assessmentEarly social communication and restricted/repetitive behaviors across settings
ScreeningM-CHAT-R/F flags risk but does not diagnose
Hearing/vision assessmentHearing impairment can mimic language delay/social nonresponse
Second-line
Comprehensive developmental evaluationSpeech/language, cognitive/adaptive, OT/sensory, educational needs
Genetic testingChromosomal microarray and fragile X commonly considered; targeted tests if indicated
Neurological workupEEG only if seizure/regression episodes; MRI if focal signs/abnormal head growth
Specialist
Developmental pediatrics/child psychiatry/neurologyComplex diagnosis, severe behavior, ID, regression, seizures, medication needs
Early intervention/school servicesStart services without waiting for final label when delay evident

Management

AAP Autism Spectrum Disorder Clinical Report 2020 and DSM-5-TR criteria
1
Intervention
  • Early intervention, speech/language therapy, OT, educational supports
  • Parent-mediated/naturalistic developmental behavioral interventions
  • Address functional communication because behavior may reflect unmet needs
2
School/family support
  • Individualized education plan with communication, social, sensory, behavioral supports
  • Caregiver training, respite, transition planning
  • Promote strengths/autonomy while addressing impairing symptoms
3
Comorbidity/safety
  • Treat sleep, constipation, feeding issues, epilepsy, ADHD, anxiety, irritability
  • Risperidone/aripiprazole for severe irritability/aggression/self-injury; monitor metabolic/EPS effects
  • Plan for elopement, water safety, bullying, abuse vulnerability

Complications

  • Language/learning impairment:
  • Epilepsy:
  • Sleep and feeding problems:
  • Anxiety/ADHD:
  • Self-injury/aggression/elopement:
  • Bullying/social isolation:
USMLE Step 2 CK Exam Tips
  • 1ASD requires social communication deficits plus restricted/repetitive behaviors
  • 2Toddler language/social regression = urgent evaluation
  • 3M-CHAT flags risk; comprehensive assessment diagnoses
  • 4Risperidone/aripiprazole treat irritability, not core ASD
  • 5Hearing test is key in language delay
  • 6Start early intervention before genetic testing returns

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Verified Sources & References

AAP Autism Spectrum Disorder Clinical Report 2020
CDC Autism Diagnostic Criteria
APA DSM-5-TR Educational Resources
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