The Effect of Sibling Order on Communication in Individuals with and without ASD

Background:  Sibling interaction can be an important positive influence in the development of children with autism spectrum disorder (ASD; Jones & Carr, 2004; Knott et al., 2007). Social and communication difficulties are core components of ASD, with deficits in adaptive use of language being common. A recent study indicated that children with ASD who had at least one older sibling showed stronger communication skills than children with ASD who did not have siblings (Ben-Itzchak et al., 2016), suggesting that older siblings promote social interaction and foster the acquisition of communication in children with ASD. It is not known whether the influence of sibling order on communication and adaptive use of language is specific to ASD or common to other neurodevelopmental disorders.

Objectives:  The present study evaluated whether sibling order has an impact on the adaptive use of language in individuals with ASD when compared to individuals with diagnoses other than autism.

Methods:  The present study utilized a clinical sample of 25 individuals (Mean age: 8.62, Range: 3-25); data collection and retrospective analyses of additional historical cases are ongoing. Seventeen individuals had an ASD diagnosis (Mean age: 7.76, Range: 3-19; diagnosis confirmed with ADOS). Eight of the seventeen individuals in the ASD cohort were oldest children. The eight individuals who did not meet criteria for ASD (Mean age: 10.43, Range: 4-25) had other clinical diagnoses (e.g., anxiety, language disorder), as evaluated by a multi-disciplinary team. Four of the eight individuals with other diagnoses were oldest children. The Vineland II Adaptive Behavior Scales – Survey Interview (VABS-II) was administered to parents, and the communication domain was used to evaluate each subject’s adaptive use of language.

Results:  T-tests revealed no significant differences in the adaptive use of communication (VABS-II) between individuals with ASD and other psychological conditions (p=.945). In the ASD group, there was a marginal effect (p=.057) with regard to sibling order, such that those who were the oldest children in their families had higher communication standard scores, thus demonstrating greater adaptive use of language. No effects of sibling order on adaptive use of language were observed in the group with other diagnoses (p=.278).

Conclusions:  The current study failed to replicate the finding that the availability of older siblings is associated with improved social communication in ASD. In contrast, preliminary results suggested that individuals with ASD may benefit from interactions with younger siblings. This may reflect conventional order effects in that oldest siblings with ASD may benefit from a developmental period with undivided parental attention. Results add to evidence indicating the benefits of siblings for the development of individuals with ASD (Shivers and Plavnick, 2015).