Communication Development in Infant Siblings of Children with ASD: Evidence of Resiliency

Background:  

Social and communication delays are considered risk indicators for ASD in late infancy to early toddlerhood.  Such delays have been identified in younger siblings of children with ASD (Landa & Garrett-Mayer, 2006).  Yet recent findings indicate that early language delays are transient in some younger siblings of children with ASD (Landa, Gross, Stuart & Bauman, 2012).

Objectives:  

Examine stability of social and language delays from late infancy through the period of expected first word acquisition. 

Methods:  

Participants are from an ongoing longitudinal study of younger siblings of children with autism (HR infants) and children at low risk for ASD (LR; no family history of autism). Data are presented from testing completed at ages 10 (22 LR; 50 HR) and 14 months (14 LR; 30 HR) (sample size will be larger by IMFAR). Frequency of initiation of joint attention (IJA) and behavior regulatory (IBR) bids as well as inventory of communicative gestures and communicative consonants were measured using the Communication and Symbolic Behavior Scales Developmental Profile (CSBS DP; Wetherby & Prizant, 2002).  Repeated measures ANOVA was used for group comparisons; post hoc analyses were conducted. 

Results:  

Significant between-group differences were found at age 10 months.  Post hocs revealed that the HR group performed significantly lower than the LR group on all four dependent variables (ps from .02 to <.001).  Longitudinal analyses revealed significant effects for Time (p = .04) and Time x Group (p=.004) for IJA, and a significant effect for Time (p<.001) for IBR.  At age 14 months, the LR and HR groups produced IJA bids with similar frequency, but the LR group produced significantly fewer IBR. From 10 to 14 months of age, the LR group’s frequency of IJA remained stable, but the HR group showed a rapid and robust increase in frequency of IJA.  The slope of the gain in frequency of initiation of IBR in the HR and LR groups was similar and parallel, but the HR group did not ‘catch up’ to the LR group in rate of producing such communicative bids.

Conclusions:  

Findings reveal global delay in the prelinguistic phase of expressive communication development in HR siblings at age 10 months, with lingering delay in isolated aspects of communication at 14 months.  The late-infancy communication delay in HR siblings is characterized by decreased overall level of producing communicative bids, whether social (IJA) or non-social (IBR) in nature, as well as by a restricted repertoire of communicative forms.  This means that the communicative bids of HR siblings are poorly differentiated and that these children are not initiating communicative engagement with others at expected rates during late infancy.  These findings have implications for resiliency in some aspects of development within HR siblings, who ‘catch up’ to LR age peers by 14 months, although they continue to show delay in frequency of behavior regulatory bids.