Having Siblings is Associated with Better Social Functioning in Autism Spectrum Disorder.

Sibling relationships play a unique developmental role, especially in emotional and social domains. In autism spectrum disorder (ASD), social-communication skills are often impaired in comparison to typical development. Therefore, studying siblings' effects on social skills of the child with ASD is important. This retrospective study examined how autism severity and functioning were affected by having older and younger sibling/s, the sex of the index child and of the sibling, and the number of siblings. The study population included 150 participants with ASD (mean age = 4:0 ± 1:6), divided into three equal groups (no sibling, older and younger siblings), matched for cognitive level. The evaluation included neurological and standardized behavioral, cognitive, and functional assessments. Children with ASD with older siblings showed less severe social interaction deficits and better social adaptive skills than only children. No significant differences in autism severity and adaptive functioning were noted between the group with younger siblings and the other groups. The more older siblings the affected child had, the better their social functioning. The sex of the participants with ASD and that of the sibling were not associated with social functioning. Social interaction deficits, the presence of older or younger siblings for children with ASD, and higher cognitive ability contributed significantly to the explained variance (48.9%) in social adaptive skills. These findings emphasize that older siblings positively influence the social skills of their younger sibling with ASD. The effect of typically developing younger siblings was modest and seen only in children with ASD and better cognition.