Continuity in social communication development among school-aged siblings of autistic children

Prospective studies of later born siblings of autistic individuals often focus on predicting autism diagnosis. Studies concentrating on siblings who do not develop autism have found subclinical atypicalities in some children as early as the first year of life. However, when followed to school-age, the continuity of these findings has been mixed. We tracked nonautistic siblings (n = 151 higher familial likelihood of autism, n = 115 lower likelihood) longitudinally from infancy to 6-16 years of age when participants completed a battery of social communication measures (parent report and direct observation/administration). Using latent profile analysis, we derived groupings based on patterns of performance across measures. Three groups were identified: Class 1 (45.5%), Class 2 (45.2%), and Class 3 (9.3%)-characterized by higher, intermediate, and lower school-age social communication abilities, respectively. We then examined the performance of these classes on independent measures of pragmatic language, reciprocal social interaction, and cognition. Class 3 demonstrated social communication differences that were most evident with novel interactive partners (e.g., examiners) and scored lower on IQ and academic achievement measures, indicating that social communication differences captured by the latent profile analysis were part of a broader pattern of developmental differences. Using data collected in the first 3 years of life, we found that the school-age classes began showing differences by 12-18 months of age-evidence of continuity between early behavior and later development. Findings suggest that when early childhood challenges are observed in siblings of autistic children, even those not meeting criteria for autism, they should be monitored over time and additional support offered as needed. (PsycInfo Database Record (c) 2026 APA, all rights reserved).