Early Signs of Autism Spectrum Disorder (ASD)
The most reliable early markers of ASD between 12 and 24 months of age include reduced levels of social attention and communication, increased repetitive behaviors with objects, abnormal body movements, and temperament dysregulation. 1
Core Early Signs (12-24 months)
Social Communication and Interaction
- Reduced social attention, including decreased eye contact and diminished response to name being called 1
- Limited or absent joint attention behaviors (inability to share focus with others about objects or events) 1
- Decreased use of gestures for communication 1
- Limited or absent pointing to show interest 1
- Lack of sharing enjoyment or achievements with others 1
- Reduced or absent social smiling and engaging in back-and-forth social interactions 1
Repetitive Behaviors and Restricted Interests
- Atypical use of objects such as spinning, lining up, or rotating items 1
- Repetitive actions or posturing of body, arms, hands, or fingers (including hand flapping and finger flicking) 1
- Unusual sensory interests or sensitivities 1
Temperament and Regulation
- Temperament profiles characterized by lower sensitivity to social reward cues 1
- Negative affect and difficulty controlling attention and behavior 1
- Emotional dysregulation and reduced attentional flexibility 1
Developmental Trajectories
- Slowing in acquisition of new skills during the second year of life 1
- Plateauing or regression of previously acquired language or social skills 1
- Atypical trajectories in early language and nonverbal development 1
Important Considerations
Age-Related Differences
- Before 12 months: Reliable behavioral markers have not yet been consistently identified 1
- Most children with ASD show clear signs by 18-24 months, though parents often report concerns earlier 1
- Despite early signs, the average age of diagnosis in the US remains 4-5 years 1
Variability in Presentation
- Considerable individual differences exist in how ASD manifests 1
- Some children show behavioral differences from the earliest months of life, while others present with speech delay in the second year or experience regression after a period of typical development 1
- This variability in behavioral profiles and developmental course must be considered when evaluating early signs 1
Clinical Implications
Screening and Referral
- The American Academy of Pediatrics recommends screening at 18-24 months to promote earlier diagnosis 1
- When concerns about early signs are raised by parents or observed by healthcare professionals, referral for autism-specific screening and comprehensive evaluation is recommended 1
- Universal screening at 18 months may identify children when symptoms are milder and more amenable to intervention, while repeated screening at 24 months can detect children missed by earlier screening 2
Early Intervention
- Early identification allows for timely intervention, which can significantly improve developmental outcomes 3, 4
- Specialized interventions can target social communication, language development, and behavioral challenges 3, 5
- Early diagnosis enables families to access appropriate support services and educational resources 3, 4
Common Pitfalls to Avoid
- Waiting for language delay as the primary indicator, when social communication differences often appear earlier 1
- Overlooking subtle social communication differences in children with otherwise typical development 1
- Attributing early signs to other factors such as shyness or hearing problems without appropriate evaluation 1, 3
- Delaying referral for comprehensive evaluation after initial screening concerns 1, 2
- Failing to recognize the variability in symptom onset and developmental trajectories 1