Date of Completion

7-11-2012

Embargo Period

7-10-2012

Open Access

Open Access

Abstract

Restricted and repetitive behaviors (RRBs) are core features in autism spectrum disorders (ASD). Previous literature has subdivided RRBs into low and high levels. Low-level behavior is characterized by a repetition of movement, such as stereotyped movements, whereas high-level behavior includes insistence on sameness and rigid adherence to a routine. There is conflicting evidence frequency and severity of RRBs in early development in children with ASD. In the current study, we examined developmental differences in the frequency and severity of RRBs in children with ASD (n = 109) compared to children with developmental delays (DD) (n= 34). Participants were evaluated at age 2 and 4, and individual items from the Autism Diagnostic Interview were categorized as low or high level and assessed for changes in frequency and severity over time. Consistent with the literature, results show an overall significant increase in the number of RRBs over time in children with ASD, but not those with DD. Specifically, the data showed an increase in high-level behaviors, with no significant change in the frequency of low-level behaviors. RRBs were then examined in relation to other developmental markers. In children with ASD, the severity of low-level RRBs was negatively correlated with level of intelligence and adaptive functioning, even when controlling for IQ. In addition, children with greater ASD symptom severity were more likely to display more severe RRBs. This suggested that both high- and low-level behaviors are present in 2-year-old children with ASD, who then experienced a significant increase in the frequency of high-level behaviors by age 4, suggesting that when making early diagnoses it is important to continue examining RRBs in relation to other social-communicative markers. Unlike at age 4 where group differences were obtained for both types of RRBs, differences in the frequency of only high-level behaviors were obtained at age 2, suggesting that simple repetitive behaviors do not differentiate 2-year-olds with ASD from those with DD. Furthermore, in children with ASD, the development of low-level repetitive behaviors are associated with lower levels of cognitive functioning, which may interfere with everyday tasks of social and communicative development and be positively related to ASD symptom severity.

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