Autism Symptomatology Associated with Developmental and Adaptive Behavior in Infants with Fragile X Syndrome and Autism Infant Siblings

Background:   Fragile X syndrome (FXS) is the number one single-gene cause of autism spectrum disorder (ASD) with approximately 35% of males with FXS meeting criteria for autism. Previous research has examined relationships between ASD symptomatology and both adaptive behavior and cognitive functioning in idiopathic ASD.  Findings suggest significant, but small, negative correlations between both adaptive communication and socialization skills, and verbal and performance IQ with ASD symptomatology (as measured by the ADOS) in adolescents (Klin et al., 2007) and between adaptive communication and daily living skills and ASD symptomatology in toddlers (Ray-Subramanian et al., 2011). Correlations between developmental measures and ADOS scores were not reported in the toddler sample. To our knowledge, no published study has examined the relationship of adaptive behavior and developmental skills to autism symptomology in infants at risk for ASD.

Objectives:   Preliminary data from an ongoing study expands this literature by examining the relationships between autism symptomatology and both cognitive and adaptive functioning in infants at risk for ASD (FXS and autism infant siblings) utilizing the Autism Observation Scale for Infants (AOSI, Bryson et al., 2008), a standardized measure of autism features in infants. 

Methods:   Participants included 20 male infants at 12 months of age who are part of a longitudinal study examining early development in infants at risk for ASD.  Infant siblings of a child with autism (ASIB, n=11) and infants with FXS (n=9) participated. Measures of autism symptoms (AOSI), developmental skills (Mullen Scales of Early Learning), and adaptive functioning (Vineland Adaptive Behavior Scales II – Survey Interview Form) were obtained. Pearson product moment correlations were run to examine the relationship between AOSI total scores and domain standard scores on the Vineland and age equivalent scores on the Mullen. Age equivalents were used on the Mullen to combat floor effects evident in the standard scores that were not observed in the Vineland. 

Results:   Correlations reveal a moderate negative relationship between the AOSI and the Expressive Language (r =-.60; r = -.52) and Fine Motor (r =-.62; r = -.59) domains of the Mullen for the ASIBs and FXS infants respectively.  These results suggest that increased autism symptoms were associated with decreased expressive language and lower fine motor skills in both groups at high risk for autism. There was no relationship between the AOSI and other domains of the Mullen and Vineland for either group.

Conclusions:   These findings are congruent with findings in older-aged samples, that higher autism symptomatology is related to lower verbal and motor functioning (Landa et al., 2013). Understanding early developmental profiles in children at heightened risk for ASD is critical to facilitate early diagnosis and guide targeted treatment to help ameliorate symptoms in key developmental periods. This study is the first to examine relationships between ASD symptomotology and both adaptive behavior and developmental skills in infants at risk for ASD. We anticipate data from at least 8 additional participants (4 in each group) by conference presentation time.