Examining the Possible Impact of Specific Symptoms of Autism Spectrum Disorder on the Social and Behavioral Adjustment of Typically Developing Siblings

Background: Sibling relationships are known to have a significant impact on the process of social and emotional development (Dunn, 1988).  A number of studies have focused on potential challenges faced by typically developing (TD) siblings of children who have developmental disability, including autism spectrum disorder (ASD) (Bagenholm & Gillberg, 1991; Knott, Lewis & Williams, 1995; Opperman & Alant, 2003; Hastings, 2007; Barr, McLeod & Daniel, 2008).  This study aims to examine how the varying symptom presentation in children with ASD may impact the adjustment of their TD siblings.  

Objectives: Based on exploratory analysis examining the relationship between symptoms seen in children with ASD and the adjustment of their TD siblings, the current study aims to further clarify this relationship.  We hypothesized that probands who have an increased presence of RRBIs are more likely to have siblings with social and behavioral difficulties.

Methods: Participants were a group of 298 families with at least one child with ASD and one TD sibling, drawn from the Simons Simplex Collection (SSC). Probands had a diagnosis of ASD confirmed using DSM-IV-TR criteria, the ADOS, and the ADI-R. In addition, as part of this study, an extensive battery of cognitive, developmental, and behavioral measures was administered.  Overall severity of the proband’s symptoms was calculated using the Calibrated Severity Score (CSS) (Gotham, Pickles, & Lord, 2009).  Neurotypical development in the TD sibling was also confirmed.  Parents completed the Social Responsiveness Scale (SRS), as well as measures to characterize the emotional and behavioral development of their TD child, including the Vineland Adaptive Behavior Scales- II (VABS-II), and the Child Behavior Checklist (CBCL).

Results:  As hypothesized, an increased presence of RRBIs on the ADI in the proband was associated with elevated scores on the social subdomain of the CBCL as well as the externalizing subdomain of the VABS-II for the TD sibling.  Specifically, higher scores on Preoccupations and Circumscribed Interests (subdomain A), was significantly associated with sibling maladaptive externalizing behaviors at p<.05.  Higher scores on Compulsions and Rituals (subdomain B), was significantly correlated with sibling social problems at a p< .01 level.  Further, more difficulty on the Social domain of the ADI-R by the proband was found to be significantly associated with social problems in the TD sibling (p<.05).  In testing for birth order effects, when proband was older, TD siblings tended to have elevated maladaptive externalizing behaviors (p<.05).  Additionally, when testing for gender effects, same gender sibling pairs also predicted increased VABS externalizing behaviors in the TD sibling (p<.01).  All models were controlled for IQ.  CSS as well as all ADOS domains yielded no significant correlations.  

Conclusions: There were a number of associations seen between proband and TD sibling behaviors, indicating that TD siblings of children with particular symptoms of ASD may be at increased risk for social and behavioral difficulties.  Since this was a cross sectional study, causality cannot be determined with these data.  Further studies will be required to better understand the complexity of these sibling relationships.