Early Childhood Language In Autism Spectrum Disorders and Fragile X Syndrome

Background: Autism spectrum disorders (ASD) share similarities with other neurodevelopmental disorders including fragile X syndrome. ASD is currently diagnosed based on behavioral manifestations whereas fragile X (fraX) is a specific genetic disorder caused by mutations of the FMR1 gene on the X chromosome, which leads to reduced production of the fragile X mental retardation protein FMRP (Vekerk et al., 1991). At least one third of individuals with fraX also receive a diagnosis of ASD and another third have significant autistic behavior (Hatton et al., 2006; Rogers et al., 2001). Behavior, cognitive development and social cognition in ASD and fraX have often been studied and compared between the two disorders. However, language profiles in ASD and fraX have not been compared extensively. Such a comparison is warranted given that receptive language is thought to be more impaired in adolescents and young adults with fraX and a co-occurring ASD diagnosis than those with fraX but without ASD (Lewis et al., 2006).  

Objectives: We compared language development in ASD and fraX during early childhood and assessed whether cognitive, social, and/or behavioral aspects of the ASD and fraX profiles contribute to atypical language development in these populations.

Methods: Participants. Fifteen boys with ASD, 37 with fraX, 11 with developmental delay (DD), and 14 typical development (TD) aged between 1 to 5 years old were assessed at two time points, with a period of approximately 24 months between time 1 and time 2 assessments for each participant. Materials. The Preschool Language Scale (PLS-4 at time 1 and 2) was administered to assess receptive and expressive language and the aberrant behavior checklist (ABC at time 2 only) was completed by parents to assess their son’s social and behavioral profile. IQ (cognitive profile) was obtained with the Mullen Scales of Early Learning. Participants in the ASD and fraX group completed the standardized measures of autism symptomatology (Autism Diagnostic Observation Schedule and Interview: ADOS-G and ADI-R). 

Results: From time 1 to time 2, PLS-4 standard scores for receptive language increased for the ASD group (p = .03) while expressive language remained stable. Receptive and expressive language scaled scores remained stable for both fragile X and TD groups and increased for the DD group (p_{comprehension}<.01, p_expression = .02). For all groups combined, PLS-4 standard scores at time 1 and 2 were significantly negatively correlated to stereotypy and hyperactivity subscales of the ABC at time 2 (p<.01) and were significantly positively correlated with fine motor and visual reception subscales of the Mullen at time 2 (p<.01). For the ASD and fraX groups, ADOS scores for social interaction at time 1 were significantly negatively correlated with PLS-4 expressive language at time 1 but not at time 2 (p<.01).

Conclusions: Language development in early childhood is associated with cognitive function, social interaction, and behavior in ASD and fraX. Children with autism present a discrepancy between receptive and expressive language while language profiles are more homogenous in children with fragile X. Findings support continued research into early language assessment and intervention for children with ASD and fragile X.