Young Adults’ Sibling Relationships: The Role of Parental Differential Treatment and the Broader Autism Phenotype

Background:

Research highlights that parental differential treatment (PDT) has negative implications for sibling relationships (e.g., Jensen et al., 2013). This pattern extends into young adulthood, when positive relationships between siblings may be particularly important for those with autism spectrum disorders (ASD). Examining Broader Autism Phenotype (BAP) characteristics in the context of PDT is important because nonclinical traits of autism may moderate sibling processes.

Objectives:

The aim of this study was to examine how PDT is associated with young adults’ sibling relationships. Because characteristics of developmental disabilities may change the nature of PDT within families (e.g., Tudor et al., 2017), we examined whether links between PDT and sibling relationships were moderated by BAP characteristics.

Methods:

Data came from a larger study about sibling influence in young adulthood, which included 866 young adults from the United States, recruited through Amazon Mechanical Turk. Young adult participants were in their mid 20s (M age = 25.43, SD = 2.54) and had about two siblings (M = 2.48, SD = 1.53; 58% female; 73% white). Participants reported on their relationship with their closest aged sibling and up to five additional siblings. In total, the 866 participants reported on PDT (6 items; Plomin & Daniels, 1985), sibling closeness (5 items; Bylth et al., 1982), and sibling conflict (3 items; Bylth et al., 1982), with 1,050 different siblings. Participants reported on their own BAP characteristics and those of each of their siblings via the Autism Spectrum Quotient (AQ; Baron-Cohen et al., 2001).

Results:

Multi-level modeling was used to account for the nature of multiple sibling relationships nested within individuals. Separate hierarchical models were tested for each dependent variable: sibling closeness and sibling conflict. Each dependent variable referred to a relationship with a unique sibling. In the first step, we included family demographic controls, ratings of PDT of the mother and father, the participant’s BAP characteristics, and each sibling’s BAP characteristics. In the second step, four two-way interactions were included: maternal PDT X participant BAP, maternal PDT X sibling BAP, paternal PDT X participant BAP, paternal PDT X sibling BAP.

Young adults reported less sibling closeness when they were higher in BAP characteristics, their sibling was higher in BAP characteristics, their mother showed higher levels of PDT, or their father showed higher levels of PDT. Interactions of maternal and paternal PDT with the sibling’s BAP also emerged. Testing of the simple slopes revealed that when the sibling was high in BAP characteristics, there was a negative association between maternal PDT and sibling closeness (see Figure 1). There was no association when the sibling was low in BAP characteristics. For paternal PDT (see Figure 2), when the sibling was low is BAP characteristics there was a negative association between PDT and sibling closeness. There was no association when the sibling was high in BAP characteristics.

Conclusions:

These findings suggest that PDT from mothers and fathers may have implications for sibling relationships in young adulthood and that BAP characteristics may moderate the ways PDT is linked to those relationships.