2016 Gatlinburg Conference Poster
PS-37
Title: Minimally Verbal Children with ASD and Cognitive Impairment: Do Definitions Matter?
Authors: Vanessa Hus Bal, Terry Katz, Somer L. Bishop
Introduction: "High functioning" children with ASD (generally defined by IQ>70) show substantial variability in the nature and
range of their language deficits. Some exhibit verbal skills below expectations based on their nonverbal cognitive abilities,
suggesting that language and cognitive functioning are, to some extent, separable dimensions in children with ASD. There is very
little information about associations between cognitive functioning and language in individuals with low nonverbal skills (IQ<70).
Indeed, references to "low-functioning" children tend to confound cognitive and language impairment, despite evidence that
some younger minimally verbal (MV) children have higher nonverbal cognitive skills (Munson et al., 2008).
Many definitions of MV children have been utilized, but it remains unknown how stratification methods compare. This study
examines: 1) how using different instruments to define MV cohorts affects sample characteristics (demographics; ASD symptom,
cognitive and adaptive profiles); 2) the overlap between cognitive and verbal abilities to identify areas in which MV children may
be compared to children with IQ<70.
Methods: Children with ASD between 6 and 18 years old (N=2044) were drawn from the Simons Simplex Collection. All children
had information from the Autism Diagnostic Interview-Revised (ADI-R), Vineland, Autism Diagnostic Observation Schedule
(ADOS), cognitive assessment and parent questionnaires. Children were divided using the following MV definitions: ADOS
Module 1 (No words/Some words), ADI-R language level (<5 words, 5+ words/no flexible phrases), Vineland Expressive age
equivalent (<18 months), Social Communication Questionnaire (item 1 indicating no phrases) and parent estimate of vocabulary
(none, 1-5, 5-25 words). Within children with NVIQ <70, MV children (ADOS Module 1, some words vs. no words) and verbal
children (ADOS Module 2-4) were compared.
Results: 328 children (16% of the sample) were classified as MV. Of the 328, 24% were MV on two instruments and 38% on
three or more. Most children (93%) were administered an ADOS Module 1 and 61% were reportedly not using daily, flexible
phrases (ADI-R). Defining MV on the basis of the ADOS Module 1 yielded the largest group with the most discrepancies across
measures (e.g., 62% MV on the ADI-R). Across MV definitions, 44-60% of children had VIQ<NVIQ profiles (i.e., VIQ 1+ SD below
NVIQ), with as many as 15% of children with NVIQ>70.
Within the NVIQ<70 group (n=507), MV children were younger (F(2,504)=12.63, p<.001) and had lower VIQ (F(2,504)=222.97,
p<.001) and NVIQ (F(2,504)=122.95, p<.001) compared to verbal children. A higher proportion of MV children (45%) had
VIQ<NVIQ profiles than verbal children (20%; X2=78.82, p<.001). MV children had less severe current social-communication
impairments on the ADOS (F(2,504)=24.38, p<.001), but more past symptoms on the ADI-R (F(2,504)=34.59, p<.001).
Discussion: This study demonstrates the variability in MV status depending on how it is defined. While no single approach is
obviously "best," these results will inform methods to identify MV children within existing samples and design of studies
ascertaining new samples of MV children. Within children with NVIQ<70, verbal and MV children differed on several
characteristics. Nearly half of MV children exhibited VIQ<NVIQ profiles, suggesting a distinct subgroup of MV children whose
language impairments are not attributable to general cognitive impairment. This highlights the need for future research to
understand the unique strengths and challenges of MV children with ASD.
References/Citations:
• Kasari, C., et al. (2013). Assessing the Minimally Verbal School-Aged Child with Autism Spectrum Disorder. Autism
Research, 6(6), 479-493.
• Munson, J., et al. (2008). Evidence for Latent Classes of IQ in Young Children With Autism Spectrum Disorder. American
Journal on Mental Retardation, 113(6), 439-452.
• Tager-Flusberg, H., & Kasari, C. (2013). Minimally Verbal School-Aged Children with Autism Spectrum Disorder: The
Neglected End of the Spectrum. Autism Research, 6(6), 468-478.