Autism
Spectrum Disorder
A neurodevelopmental condition characterized by persistent differences in social communication, restricted interests, repetitive behaviors, and atypical sensory processing. Presents across a spectrum of support needs.
DSM-5-TR Diagnostic Criteria
Criterion A: Social Communication & Interaction Deficits
Persistent deficits across multiple contexts. All three required:
- • Social-Emotional Reciprocity (Abnormal social approach, reduced sharing of interests/emotions, failure to initiate/respond to social interactions)
- • Nonverbal Communication (Poorly integrated verbal/nonverbal communication, abnormal eye contact and body language, deficits in understanding/using gestures)
- • Relationships (Difficulty adjusting behavior to social contexts, challenges in sharing imaginative play, difficulty making friends, absence of interest in peers)
Criterion B: Restricted, Repetitive Behaviors
2+ required:
- • Stereotyped/Repetitive Motor Movements or Speech (Hand flapping, rocking, echolalia, idiosyncratic phrases)
- • Insistence on Sameness (Inflexible routines, ritualized patterns, extreme distress at changes)
- • Highly Restricted, Fixated Interests (Abnormal in intensity or focus)
- • Atypical Sensory Responses (Hyper/hypo-reactivity, unusual sensory interests, adverse response to textures/sounds)
Criterion C & D: Development & Function
Onset and impact requirements:
- • Criterion C: Symptoms must be present in early childhood
- • Criterion D: Symptoms cause clinically significant impairment in social, occupational, or other areas
Specifiers
Additional diagnostic information:
- • With or without intellectual impairment
- • With or without language impairment
- • Associated with known genetic/medical condition
- • Level of support required (Level 1, 2, or 3)
Assessment Protocols
Validated tools for screening and severity tracking
ADOS-2
Autism Diagnostic Observation Schedule, Second Edition
Criterion-standard semi-structured assessment using standardized activities to observe social-communication and restricted/repetitive behaviors.
Comparison scores (1-10); scores ≥8 suggest autism, 4-7 autism spectrum; module selected by age/language level
ADI-R
Autism Diagnostic Interview-Revised
Detailed parent/caregiver interview covering developmental history and current behaviors; complements ADOS-2.
Algorithm scores for social interaction, communication, and restricted/repetitive behaviors
M-CHAT-R/F
Modified Checklist for Autism in Toddlers, Revised with Follow-Up
Parent questionnaire for screening toddlers (16-30 months); includes follow-up interview to reduce false positives.
Low, medium, high risk based on critical items; high risk warrants immediate diagnostic evaluation
SRS-2
Social Responsiveness Scale, Second Edition
Quantitative measure of autistic traits across social awareness, cognition, communication, motivation, and restricted/repetitive behaviors.
T-scores: ≥76 severe, 66-75 moderate, 60-65 mild deficits in social interaction
Causes & Etiology
Neurobiological
- Atypical brain connectivity (reduced long-range, increased local)
- Brain volume changes in early childhood
- Abnormalities in temporal cortex, amygdala, cerebellum
- Altered excitatory/inhibitory (E/I) balance
Genetic
- Heritability: 70-90%
- Polygenic architecture: 100+ genes
- De novo mutations (SHANK3, NLGN, NRXN)
- Copy number variants (16p11.2 deletion, 15q duplication)
Environmental
- Advanced parental age
- Prenatal exposure to valproate
- Maternal immune activation
- Extreme prematurity and low birth weight
Neuropsychological
- Theory of Mind deficits
- Weak central coherence
- Executive function impairments
- Atypical sensory processing
Scientific Sources
ADOS-2 Validation
Lord C, Rutter M, et al. Autism Diagnostic Observation Schedule, Second Edition (ADOS-2) Manual. Western Psychological Services. 2012.
DSM-5-TR Criteria
American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR). 2022.
Early Intensive Behavioral Intervention
Dawson G, Rogers S, et al. Randomized, controlled trial of an intervention for toddlers with autism: the Early Start Denver Model. Pediatrics. 2010;125(1):e17-23.
Genetic Architecture of Autism
Grove J, Ripke S, et al. Identification of common genetic risk variants for autism spectrum disorder. Nat Genet. 2019;51(3):431-444.
Neurobiology of Autism
Geschwind DH, Levitt P. Autism spectrum disorders: developmental disconnection syndromes. Curr Opin Neurobiol. 2007;17(1):103-111.
M-CHAT-R/F Screening Tool
Robins DL, Casagrande K, et al. Validation of the Modified Checklist for Autism in Toddlers, Revised with Follow-up (M-CHAT-R/F). Pediatrics. 2014;133(1):37-45.
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