Psychiatry/Behavioral · PANCE / PANRE

Autism Spectrum Disorder (ASD)

Persistent deficits in social communication plus restricted/repetitive behaviors present in early development.

Also known as: autism, ASD, autism spectrum disorder

Overview

A neurodevelopmental disorder characterized by persistent deficits in social communication and social interaction across multiple contexts AND restricted, repetitive patterns of behavior, interests, or activities, with symptoms present in early developmental period and causing clinically significant impairment.

Epidemiology

Prevalence ~1 in 36 US children (CDC 2023). Male-to-female ratio ~4:1, though females may be underdiagnosed. Highly heritable (~80%).

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Risk factors

Male sex; sibling with ASD (recurrence risk ~10-20%)
Advanced parental age
Prematurity, low birth weight, perinatal complications
Genetic syndromes: fragile X, tuberous sclerosis, Rett (girls), 22q11.2 deletion
Valproate exposure in utero

Pathophysiology

Polygenic and copy-number variant contributions; abnormal cortical development and connectivity, particularly in regions subserving social cognition and language. Synaptic and neurodevelopmental gene pathways implicated.

Clinical presentation

Symptoms

Social communication: reduced social-emotional reciprocity, atypical nonverbal communication, difficulty developing and maintaining relationships appropriate to developmental level
Restricted/repetitive: stereotyped/repetitive motor movements or speech, insistence on sameness/routines, highly restricted fixated interests, hyper- or hyporeactivity to sensory input
Variable language ability — from non-speaking to fluent; pragmatic deficits common even in fluent speakers
Common co-occurrences: ID, ADHD, anxiety, epilepsy, GI symptoms, sleep disorders

Signs / physical exam

Reduced eye contact, limited joint attention, atypical play (lining up toys, lack of pretend play)
Echolalia, scripted speech
Hand-flapping, rocking, toe-walking
Sensory sensitivities (sound, texture, light)

Differential diagnosis

Intellectual disability without ASD — Cognitive impairment without disproportionate social communication deficits
Language disorder / social communication disorder — Language or pragmatic deficits without restricted/repetitive behaviors
ADHD — Inattention and impulsivity without core social-communication impairment; commonly co-occurs
Reactive attachment disorder — History of severe neglect; social withdrawal improves with stable caregiving
Selective mutism — Speaks at home but not in select settings; otherwise typical social development
Hearing impairment — Screen audiology in any child with language delay
Anxiety / OCD — Distinguish ego-dystonic compulsions from autistic restricted interests, which are typically ego-syntonic

Diagnostic workup

Diagnostic criteria

DSM-5-TR: (A) Persistent deficits in social communication and interaction across contexts — all three subcriteria (reciprocity, nonverbal communication, relationships); (B) Restricted/repetitive patterns — >=2 of four (stereotypies, insistence on sameness, restricted interests, sensory differences); (C) Symptoms in early developmental period; (D) Clinically significant impairment; (E) Not better explained by ID alone. Specify severity (levels 1-3 by support needs), with/without ID, language impairment, medical/genetic conditions, or catatonia. Screening: M-CHAT-R/F at 18 and 24 months.

Labs

Screen lead level, audiology evaluation
Genetic evaluation: chromosomal microarray and fragile X testing recommended for all; consider whole exome based on dysmorphology
Metabolic workup if regression or dysmorphic features
EEG if seizures suspected

Imaging

MRI not routine; obtain if focal findings, regression, microcephaly, or macrocephaly with neurologic signs

Diagnostic algorithm

ASD Severity	Social communication	Restricted/repetitive	Support need
Level 1	Difficulty initiating; atypical responses	Inflexibility hampers function	Requiring support
Level 2	Marked deficits even with supports	Distress with change; obvious to observer	Substantial support
Level 3	Severe deficits in functional communication	Extreme inflexibility, marked impairment	Very substantial support

DSM-5-TR Autism Spectrum Disorder severity levels.

Treatment

First-line

Early intensive behavioral intervention — applied behavior analysis (ABA), naturalistic developmental behavioral interventions (NDBI), Early Start Denver Model
Speech-language therapy; occupational therapy for sensory and motor issues
Educational supports — IEP, structured teaching
Family support and psychoeducation; respite care
Treat co-occurring conditions: ADHD, anxiety, sleep, epilepsy

Second-line / adjunct

Atypical antipsychotic — risperidone or aripiprazole (FDA-approved) for irritability/aggression/self-injury
SSRI for comorbid anxiety/OCD (avoid in repetitive behaviors alone — limited evidence)
Melatonin for sleep onset
Stimulants/non-stimulants for comorbid ADHD (response often less robust than in non-ASD ADHD)

Complications

Co-occurring intellectual disability (~30%), epilepsy (~20-30%), anxiety/OCD, ADHD, depression
Self-injurious behavior in severe cases
Sleep and feeding difficulties
Wandering/elopement
Higher rates of suicidality, especially in adults with ASD without ID
Caregiver burden

PANCE pearls

All children should be screened for ASD at 18 and 24 months using M-CHAT-R/F per AAP; refer for diagnostic evaluation if positive — do not wait.
Early intervention before age 3 produces the largest gains; do not delay services for formal diagnosis.
Catatonia is increasingly recognized in adolescents/adults with ASD — consider in regression with mutism, posturing.
Adults with ASD often present first with anxiety or depression; ask about lifelong social communication patterns.

References

AAP 2020 — Hyman SL et al. Identification, Evaluation, and Management of Children With Autism Spectrum Disorder. Pediatrics 2020
AACAP 2014 — AACAP Practice Parameter for the Assessment and Treatment of Children, Adolescents, and Adults with ASD (2014)
DSM-5-TR — American Psychiatric Association. DSM-5-TR (2022)

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