The broader autism phenotype in infancy: when does it emerge?

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.