The broader autism phenotype in infancy: when does it emerge?
Sally Ozonoff1, Gregory S Young1, Ashleigh Belding1
1University of California-Davis.
Insights
Atypical development, consistent with the broader autism phenotype, is detectable in high-risk infants by age one. Early identification in infant siblings of children with autism spectrum disorder (ASD) is crucial for timely intervention.
Area of Science:
- Developmental psychology
- Pediatric neurology
- Autism spectrum disorder research
Background:
- Infant siblings of children with autism spectrum disorder (ASD) are at higher risk for developing ASD.
- The broader autism phenotype (BAP) refers to subthreshold autistic traits observed in relatives of individuals with ASD.
- Early identification of developmental differences is critical for intervention in high-risk populations.
Purpose of the Study:
- To determine the frequency of atypical development consistent with BAP in high-risk infant siblings of children with ASD.
- To identify the earliest age at which atypical development becomes evident.
- To ascertain which developmental domains are most affected in these infants.
Main Methods:
- A prospective longitudinal study comparing 294 high-risk infants with 116 low-risk infants.
- Participants were assessed at 6, 12, 18, 24, and 36 months of age.
- Outcomes at 36 months were classified as ASD, Typical Development (TD), or Non-TD based on Autism Diagnostic Observation Schedule (ADOS) and Mullen Scale scores.
Main Results:
- 28% of high-risk infants were classified as Non-TD at 36 months.
- Significant differences in the Non-TD group emerged by 12 months of age, not distinguishable at 6 months.
- Atypical development was observed across cognitive, motor, language, and social domains, with social-communication being most affected.
Conclusions:
- Features of atypical development, consistent with BAP, are detectable by 12 months of age in high-risk infants.
- These developmental differences impact multiple domains, particularly social-communication.
- Close developmental surveillance and timely intervention are essential for infant siblings of children with ASD.
Objective:
This study had 3 goals, which were to examine the following: the frequency of atypical development, consistent with the broader autism phenotype, in high-risk infant siblings of children with autism spectrum disorder (ASD); the age at which atypical development is first evident; and which developmental domains are affected.
Method:
A prospective longitudinal design was used to compare 294 high-risk infants and 116 low-risk infants. Participants were tested at 6, 12, 18, 24, and 36 months of age. At the final visit, outcome was classified as ASD, Typical Development (TD), or Non-TD (defined as elevated Autism Diagnostic Observation Schedule [ADOS] score, low Mullen Scale scores, or both).
Results:
Of the high-risk group, 28% were classified as Non-TD at 36 months of age. Growth curve models demonstrated that the Non-TD group could not be distinguished from the other groups at 6 months of age, but differed significantly from the Low-Risk TD group by 12 months on multiple measures. The Non-TD group demonstrated atypical development in cognitive, motor, language, and social domains, with differences particularly prominent in the social-communication domain.
Conclusions:
These results demonstrate that features of atypical development, consistent with the broader autism phenotype, are detectable by the first birthday and affect development in multiple domains. This highlights the necessity for close developmental surveillance of infant siblings of children with ASD, along with implementation of appropriate interventions as needed.
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