Adjustment in Typically Developing Siblings of Children with ASD: The Impact of Sex, Age, and Birth Order
Objectives: To investigate the impact of modulating factors such as sex, age, and birth order on TD-Sib adjustment. We hypothesized that TD-Sibs younger than their sibling with ASD will exhibit more adjustment challenges compared to older TD-Sibs and age-based norms.
Methods: Thirty-four families with at least one TD-Sib (N=34, 6-12 years, mean age=8.9 years) and one child with ASD were recruited through a larger study investigating the effectiveness of a sibling support group. Prior to support group participation, one parent completed the Child Symptom Inventory-4 (CSI-4) and Behavior Assessment System for Children, Second Edition (BASC-2) to measure the TD-Sib’s emotional and behavioral adjustment. To investigate the difference in clinical/subclinical occurrences in adjustment difficulties between TD-Sibs and normative samples, binomial t-tests were conducted for each CSI-4 and BASC-2 subscale. Within the TD-Sib sample, independent sample t-tests were used to compare subscale scores between males and females, TD-Sibs younger or older than the affected sibling, and TD-Sibs younger than eight (<8) or eight and older (8+; cutoff selected to correspond to BASC-2 normative age groupings).
Results: On the CSI-4, male and female TD-Sibs showed no significant differences in adjustment and scored in the normative range on all subscales. However, the proportion of female TD-Sibs with subclinical Depression subscale scores was lower than population norms (p<0.05). TD-Sibs younger than their affected sibling had greater challenges than older TD-Sibs on BASC-2 Daily Living Skills subscale (t(29)=-2.06, p<0.05). Compared to TD-Sibs 8+, TD-Sibs <8 exhibited worse adjustment on BASC-2 Functional Communication (t(32)=2.55, p<0.05) and marginally more impairment on BASC-2 Attention (t(32)=2.01, p=0.053) and Conduct (t(32)=1.10, p=0.054) subscales. Likewise, the proportions of TD-Sibs <8 with subclinical adjustment difficulties on the BASC-2 Depression subscale was higher than population norms (p<0.05). The proportions of TD-Sibs 8+ with adjustment challenges on all CSI-4 and BASC-2 subscales were comparable to or less than population norms (BASC-2 Somatization, Withdrawal, Leadership, Functional Communication, p-values<0.05).
Conclusions: TD-Sibs did not exhibit difficulties in their parent-reported adjustment and scored in the normative range on both adjustment measures. However, our findings suggest an effect of birth order and developmental age, such that TD-Sibs younger than their affected sibling or younger than eight showed more adjustment challenges. Understanding the psychological well-being of TD-Sibs may help inform family and sibling support groups as well as sibling-mediated interventions for children with ASD.