Language growth in very young siblings at risk for autism spectrum disorder

Background: Children with autism spectrum disorder (ASD) show substantial variability in their language development. Language problems are highly prevalent in these children. In addition, the quality of early language abilities contributes to the overall development of these children and is highly predictive of their adult outcome. Yet, little is known about language development in children at risk of ASD during the first years of life. Aims: To compare early receptive language (RL) and expressive language (EL) development in children at risk of ASD and determine predictors of language development. Methods & Procedures: Developmental trajectories of RL and EL were investigated from 10 to 36 months of age in younger siblings of typically developing children (LR-sibs, N = 30) and in younger siblings of children with ASD (HR-sibs, N = 31) using the Mullen Scales of Early Learning. Furthermore, both child and demographic characteristics were examined as possible predictors of language development. Outcomes & Results: Both groups showed similar growth curves for RL and EL and the majority of the children showed average (within ±1.5 SD of the mean) or above-average language abilities. Nevertheless, the mean growth of EL was lower and the variation in growth of both RL and EL was higher in HR-sibs than in LR-sibs. Furthermore, early child characteristics were predictive of language development in both groups. Yet, some child characteristics seemed to be of more importance in HR-sibs than in LR-sibs. Consequently, lower non-verbal abilities at 10 months in both groups and a higher degree of ASD characteristics at 14 months in HR-sibs may be indicative of difficulties in language development. Conclusions & Implications: HR-sibs show more variation in their language development than LR-sibs during the first 3 years of life. The majority of HR-sibs, however, did not present with below-average language abilities. Yet, early characteristics of ASD may be a red flag for difficulties in the language development of HR-sibs.