Autism Symptom Severity As Moderator of IQ and Language Development Among Children with Delayed Phrase Speech and Autism Spectrum Disorder

Background:  Understanding barriers to language development continues to be a research focus in children with ASD. Prospective longitudinal studies have found non-verbal cognitive ability at age 2, early joint attention, autism symptom severity, and vocal/motor imitation skills to be significant predictors of language outcomes in children with ASD up to age 9. Further research is needed to better understand the relationship between these and other variables on the emergence of functional communication in children with severe language delays.

Objectives:  To examine: a) the rate at which children acquire phrase speech at or after age 4; b) differences between those children who do and do not gain language despite initial delay; and c) if  the relationship between IQ and delayed language development is moderated by autism symptom severity.

Methods:  Data came from the Autism Treatment Network (ATN) registry, a multi-site collaboration among 17 autism centers in the US and Canada. All children have a diagnosis of ASD, confirmed by the Autism Diagnostic Schedule (ADOS) and DSM-IV-TR criteria. From this repository, a total of 183 children met the following criteria for this study: a) 8 years or older (M = 10.7 y, SD = 2.3 y) and b) absence of phrase speech by age 4 years. Bivariate analyses were performed to examine demographic, cognitive, adaptive, behavioral, psychiatric, and autism symptom differences between children who developed phrase speech at or after 4 years of age and those who did not. Multivariate logistic regression analyses were used to examine if autism symptom severity moderated the relationship between IQ and the likelihood of late onset language development.

Results:  A total of 112 (61%) children developed phrase speech between 4 and 8 years, while 71 (39%) had not developed phrased speech by age 8 years or older. For those who went on to develop language, age at phrase speech onset ranged from 4 to 10 years (M = 4.7 y; SD=1.02 y). Bivariate analyses revealed that lower autism symptoms (ADOS) as well as higher nonverbal IQ and adaptive scores were associated with later language attainment (all p < .001). Mean-centered autism symptom severity and IQ scores, as well the interaction between the two, were significant in the multivariate logistic model (all p < .05).

Conclusions:  Novel to the literature, this study found the relationship between nonverbal intelligence and the development of phrase speech, despite language delay prior to 4 years of age, is moderated by autism symptoms.  This further supports the importance of evaluating and considering nonverbal skills in developing interventions and setting goals for language development; however, given the moderating relationship of autism-related behaviors, additional intervention goals targeting such interfering behaviors may provide additional benefit to language-driven intervention.

This research was conducted as part of the Autism Speaks ATN. Further support came from a cooperative agreement (UA3 MC 11054) from the U.S. Department of Health and Human Services, Health Resources and Services Administration, Maternal and Child Health Research Program, to the Massachusetts General Hospital. The views expressed in this publication do not necessarily reflect the views of Autism Speaks, Inc.