Influence of siblings on adaptive behavior trajectories in autism spectrum disorder

Siblings play an important role in shaping the developmental trajectories of individuals with autism spectrum disorder. Having siblings has been associated with better social communication, non-verbal communication, and theory of mind abilities in autism spectrum disorder. However, little is known about the impact of siblings on adaptive skill growth over time, even though adaptive behavior competencies are among the strongest predictors of positive outcomes in autism spectrum disorder. This study examined the influence of sibling constellation factors, including the presence of siblings, position in birth order, gender of closest-age sibling, and gender match of sibling dyad on the adaptive behavior trajectories of individuals with autism spectrum disorder and non-spectrum disorders from ages 9 to 26 years. Participants with one or more siblings experienced faster growth rates in adaptive behavior from childhood to adulthood than participants without siblings across both Black and White participants, although effects were magnified in Black participants. Furthermore, among participants with siblings, those with male closest-age siblings and those with gender-matched siblings, irrespective of birth order, demonstrated the steepest adaptive skill growth within their respective groups over the 17-year period. Results suggest that siblings may serve an important role in improving the adaptive functioning trajectories and overall outcomes of individuals with autism spectrum disorder. Lay abstract Siblings have the potential to shape the developmental trajectories of individuals with autism spectrum disorder. Having siblings has been associated with better social communication skills, less severe non-verbal communication deficits, and improved theory of mind abilities in autism spectrum disorder. This study examined the influence of the presence of a sibling, participant’s position in the birth order, gender of the closest-age sibling, and gender match of the sibling dyad on the rate of growth in adaptive skills from ages 9 to 26 years among individuals with autism spectrum disorder and individuals with a history of non-spectrum developmental disorders. While all participants showed consistent gains in adaptive skill development as a function of age, there was variability in rates of growth based on sibling constellation group membership. Participants with at least one sibling, regardless of other sibling constellation factors, experienced greater rates of growth in adaptive behavior trajectories from childhood to adulthood than participants with no siblings across both Black and White participants, although differences were magnified in Black participants. Furthermore, among participants with siblings, those with male closest-age siblings and those with gender-matched siblings, irrespective of birth order position, demonstrated the steepest growth patterns in adaptive functioning within their respective groups over the 17-year period. Results suggest that siblings may serve an important role in improving the adaptive functioning trajectories and overall outcomes of individuals with autism spectrum disorder.

Theory of mind in children with and without autism spectrum disorder: Associations with the sibling constellation

The two prior studies that have examined associations between the sibling constellation and theory of mind in autism spectrum disorder yielded discrepant findings. Thus, efforts to better understand the sibling–theory of mind link in autism spectrum disorder are necessary. This study examined a sample of prekindergarten- and kindergarten-aged (i.e. 4–6 years) typically developing children ( n = 39) and verbal children with autism spectrum disorder ( n = 61). Sibling presence, number of siblings, and having younger and older siblings were positively associated with theory of mind in typically developing children, but not in the full sample of children with autism spectrum disorder. However, in the subgroup of children with autism spectrum disorder without sibling recurrence, the presence of at least one older sibling was positively associated with theory of mind. Findings expand previous limited research on the sibling–theory of mind link in children with autism spectrum disorder by demonstrating a potential difference in the influence of the sibling constellation between children from simplex and multiplex families.

Siblings and the Development of Prosocial Behaviour

The frequency of sharing, helping, comforting and cooperative behaviour shown by young siblings towards one another, their response to the other child's distress, and the relation between this prosocial behaviour and conflict behaviour was studied in 43 2-child families observed at home when the second child was 18 and 24 months old. By 18 months children were capable of sharing/helping/comforting, but apparently rarely motivated to respond in this way; in contrast cooperative behaviour was frequently shown. Conciliation, teasing and cooperative behaviour was more frequently shown by 2-year-olds whose siblings had previously been cooperative, and similarly conciliation and distraction was most frequently shown by older siblings whose younger siblings had shown cooperative behaviour 6 months previously. Sibling constellation variables did not account for individual differences in prosocial behaviour.