Early Detection and Development of Autism Spectrum Disorder in Toddlerhood

Early Signs and Development of ASD

Reduced levels of social attention and social communication, along with increased repetitive behavior with objects, are established early markers of ASD between 12 and 24 months of age, according to the American Academy of Pediatrics 1
Additional potential markers include abnormal body movements and temperament dysregulation during this developmental period, as reported by the American Academy of Pediatrics 1
By age 12 months, significant differences can be observed between children who will later be diagnosed with ASD and typically developing children, with slower growth in language skills becoming apparent, as noted by the American Academy of Pediatrics 2
Some children with ASD show behavioral differences from the earliest months of life, while others present with speech delay in the second year, and some are described as becoming withdrawn and losing skills after a period of relatively typical development into the second year, according to the American Academy of Pediatrics 1

The second year of life is a particularly critical developmental period for children with ASD, as it is a dynamic period of brain growth during which increases in brain volume and atypical connectivity associated with ASD first emerge, as reported by the American Academy of Pediatrics 3
Declining trajectories of social communication behavior and loss of skills are observed in most infants with later ASD diagnosis, according to the American Academy of Pediatrics 2
By 18 months, significant differences in development are noted between children with ASD and typically developing children, as noted by the American Academy of Pediatrics 2

The Modified Checklist for Autism in Toddlers (M-CHAT) shows lower positive predictive value in younger children (16-23 months) compared to older toddlers (24-30 months), as reported by the American Academy of Pediatrics 4
Despite lower specificity for autism at 18 months, the positive predictive value for any diagnosable developmental disorder is high, according to the American Academy of Pediatrics 4

Early detection and screening aim to ensure that children with ASD can access evidence-based interventions to provide the best opportunity for optimal development and outcomes, as recommended by the American Academy of Pediatrics 5
Interventions during the second year may counter the developmental cascade that contributes to progressive symptom development, as reported by the American Academy of Pediatrics 3

Failure to respond to name at 12 months is highly suggestive of developmental abnormality, according to the American Academy of Pediatrics 6
Fewer nonverbal behaviors to initiate shared experiences, significant differences in initiation of joint attention, and less frequent eye contact are also early signs of ASD, as reported by the American Academy of Pediatrics 6

The American Academy of Pediatrics (AAP) recommends universal ASD-specific screening at 18 and 24 months of age during routine well-child visits 7, 8
Siblings of children with ASD require intensified surveillance with screening at minimum at 18 and 24 months due to their elevated risk (14-18%) 9
Some signs of ASD can be detected as early as 12 months, though screening before 18 months may have higher false-positive rates 10

For children 16-30 months: Modified Checklist for Autism in Toddlers (M-CHAT) is recommended as both a level 1 and level 2 screening tool with strong evidence supporting its use 10
For high-risk children aged 14-36 months: Screening Tool for Autism in Two-Year-Olds (STAT) shows high sensitivity (92%) and specificity (85%) 9

Implement universal ASD screening at 18 and 24 months using validated tools like M-CHAT 8
Conduct ongoing developmental surveillance at all well-child visits 7
Immediately refer children who screen positive for ASD for comprehensive diagnostic evaluation and appropriate early intervention services 9
For siblings of children with ASD, maintain heightened vigilance with continuous developmental surveillance 9