Over the past several years, numerous studies have reported improvements in restricted and repetitive behaviors (RRBs) as individuals with autism spectrum disorders (ASD) enter adulthood. These studies have yielded important findings, but are limited by aspects of their design, including reliance on retrospective parent report and use of cross-sectional data to make inferences about how behaviors change over time.
Objectives:
The primary aim of the present study is to learn more about the development of RRBs in ASD from childhood to adulthood. The study uses a longitudinal sample of children diagnosed with ASD at a very young age and repeatedly assessed throughout childhood and into early adulthood. The fact that the same individuals underwent repeated assessments using the same measures, and that parents were asked to report about their children’s current behaviors, allows us to make stronger conclusions about how RRBs change over time in ASD.
Methods:
Data were collected as part of a longitudinal study of toddlers referred for possible autism. Children were seen at approximately 2, 3, 5, 9, and 18 years of age. At each wave, children completed a battery of cognitive and diagnostic measures. Parents completed several questionnaires and interviews. RRB data for this study were obtained from the Autism Diagnostic Interview-Revised. At all waves (except the age 3 assessment), each child was assigned a consensus best-estimate clinical diagnosis of ASD (autism or pervasive developmental disorder-not otherwise specified) or a non-spectrum developmental disorder. Of the 161 children diagnosed with ASD at age 2, data are currently available for 78 participants. Data for approximately 20 additional participants will be available shortly.
Results:
Most behaviors were present in a substantial proportion of the young adults. Prevalence rates ranged from 22% for unusual preoccupations to 54% for unusual sensory interests and hand/finger mannerisms. Consistent with previous studies, there was also abatement of all RRBs over time; substantial proportions of those who had reportedly exhibited a behavior at one or more of the previous waves no longer exhibited that behavior at age 18. Rates of abatement ranged from 31% for circumscribed interests to 89% for resistance to trivial changes in the environment. For nearly all behaviors, those who showed abatement at age 18 had higher non-verbal IQ scores at age 2 than children who did not show abatement, but the only statistically significant result was for unusual sensory interests, t(70) = -2.4, p < .05.
Conclusions:
These initial findings provide further evidence for improvement in RRBs as individuals with ASD enter adulthood. Abatement may be associated with higher early NVIQ scores; this relationship requires further examination. Further analyses will examine RRBs subtypes (e.g., ‘repetitive sensorimotor’ versus ‘insistence on sameness’). We will determine whether trajectories of RRB development vary depending on the RRB subtype, and whether individual variables (e.g., IQ) predict patterns of change in RRB subtypes over time. Findings from the present study will have implications for the identification of subtypes of ASD based on RRB trajectories, and for our understanding of the prognosis of RRBs for different subgroups.
See more of: Clinical Phenotype
See more of: Symptoms, Diagnosis & Phenotype