Measurement of Restricted, Repetitive Patterns of Behavior and Interests Using the CSBS In Children with ASD In the Second Year of Life

Background:  Restricted and repetitive patterns of behaviors, interests, and activities is a core diagnostic feature in the draft DSM-5. Previous research on a smaller sample found that children with autism spectrum disorder (ASD) demonstrate repetitive and stereotyped behaviors during the second year of life (Morgan, Wetherby & Barber, 2008; Watt et al., 2008); however there is no evidence that restricted interests can also be identified in this age group.

Objectives:  The purpose of this study of the FIRST WORDS Project was to measure repetitive and stereotyped behaviors and fixated interests in children with ASD, developmental delay (DD), and typical development (TD) from 18 to 24 months of age. 

Methods:  Communication and Symbolic Behavior Scales (CSBS; Wetherby & Prizant, 2002) Behavior Samples were video recorded for 100 children later diagnosed with ASD, 80 children with DD, and 100 children with TD. The samples were rated using the Repetitive Movement and Restricted Interests Scales (RMRI), a new companion to the CSBS. Scores were computed for the rate and inventory of repetitive or stereotyped behaviors, including repetitive movement or posturing of the body (RMB) and repetitive or stereotyped movement with objects (RMO); as well as restricted or fixated interests, including clutching objects across activities (CLCH), sticky attention to objects (STCK), and excessive interest in objects or actions (EXCS). Measures of developmental level using the Mullen Scales of Early Learning (MSEL; Mullen, 1995) and autism symptoms using the Autism Diagnostic Observation Schedule (ADOS; Lord et al., 1999) were obtained at an average age of 37.0 months (SD=7.71).

Results:  Preliminary analyses of 85 samples indicate that the ASD group displayed significantly higher overall rates of both repetitive behaviors and restricted interests than the TD and DD groups. Specifically, the ASD group displayed significantly higher rates of RMB, RMO, and EXCS than the TD group and significantly higher rates of RMO and STCK than the DD group. There was large variability and no significant group differences in rates of CLCH. In children with ASD and DD, rates of repetitive and stereotyped behaviors were significantly correlated with MSEL verbal and nonverbal developmental quotients as well as ADOS algorithm scores. There was no significant correlation between MSEL scores and restricted or fixated interest rates; however these rates significantly correlated with ADOS Social Affect domain.

Conclusions:  Both restricted and repetitive patterns of behaviors and interests were evident in children with ASD late in the second year using the RMRI with the CSBS behavior sample. These findings have important implications for the utility of the DSM-5 draft diagnostic criteria to identify symptoms during a structured observation in very young children with ASD.