Siblings of Individuals with and without Autism Spectrum Disorder and Other Intellectual Disabilities

Background: Research on siblings of individuals with intellectual and developmental disabilities (IDD) is a relatively small field, with roots in early qualitative studies. While many early studies did not distinguish outcomes based on the nature of the brother or sister’s disability, more recent studies have focused on siblings of individuals with autism spectrum disorder (ASD). 

Objectives: The present study compares behavior and functioning among individuals with autism spectrum disorder, typically-developing individuals (TD), and individuals with other intellectual and developmental disabilities (IDD), as well as emotional outcomes for siblings of these individuals.

Methods: Data was collected as part of a study comparing adolescent siblings of individuals with and without intellectual and developmental disabilities. The present study included a total of 49 families of adolescents with an IDD, 26 of whom had a child with an ASD diagnosis, and 48 families of typically-developing children. Families were eligible to complete the online survey if there were only two children, both of whom were between the ages of 12 and 18 and living at home. A parent completed measures of behavior, functioning, and impact on the family for the child with ASD/IDD (the “target child”), as well as a measure of parental optimism. The "sibling" (child without autism or IDD) completed self-report measures of empathy and emotionality toward the target child. Groups were then compared using chi-squares and ANOVAs.   

Results: Target children in the ASD group had significantly more behavior problems (F=15.77, p<.001), negative impact on the family as a whole (F=15.65, p<.001), and negative impact on the sibling (F=28.23, p<.001) than target children in both the TD and IDD groups. Parents of children in the TD group reported less financial burden (F=30.88, p<.001) than parents of children in the ASD and IDD groups, as well as higher levels of target child functional abilities (F = 49.35, p<.001) while parents of children in the ASD group reported lower levels of optimism than parents of children in the TD and IDD groups (F=5.89, p<.01). Siblings did not show any differences in empathy based on their brother/sister’s disability, but siblings of children in the ASD and ID groups reported feeling more anxiety toward the target child than did siblings in the TD group (F=10.36, p<.001)    

Conclusions: These analyses reveal fascinating patterns of target child behavior and sibling outcomes. Though target children in the ASD group had significantly more behavior problems than target children in the IDD group, siblings of children with ASD did not report any different outcomes than siblings in the IDD group. While previous research has found that target child behavior problems predict sibling outcomes, in the present study, behavior problems did not differentiate sibling emotionality. Additionally, while parents of children with ASD reported more negative impact on the sibling than parents of children in the IDD group, sibling self-report revealed no differences in outcomes between the two groups, highlighting the importance of multiple informants when studying siblings.