Measurement of Subcategories of Repetitive Behaviors in Autistic Adolescents and Adults

Abstract

Background:

Restricted and repetitive behaviors (RRBs) are core features of autism. Factor-analytic studies composed primarily of children have provided evidence for two domains of RRBs: Repetitive Sensory Motor (RSM) and Insistence on Sameness (IS) behaviors. The present study explores the validity of the Autism Diagnostic Interview-Revised (ADI-R) and the Repetitive Behavior Scale-Revised (RBS-R) for assessing these RRB subtypes in autistic adolescents and adults.

Methods:

The sample included 293 participants (M_age = 19.89 years, SD_age = 4.88 years) whose RRBs were assessed via ADI-R, RBS-R Caregiver Report or RBS-R Self-Report. Confirmatory factor analysis (CFA) was conducted to assess the validity of the two-factor structure for each instrument. Cronbach's alpha was computed to assess subscale reliability. Correlations were examined between instrument subscales and nonverbal intelligence quotient (NVIQ) and age.

Results:

Exploratory correlations were modest and provided weak evidence in favor of the utility of a CFA for the ADI-R. The RBS-R Caregiver and Self-Report CFA and internal consistencies supported the two-factor RSM and IS model tested. Consistent with previous literature, NVIQ was negatively correlated with the RBS-R Caregiver RSM subscale, but not meaningfully associated with IS. Neither RBS-R Self-Report subscale was meaningfully correlated with NVIQ. Across instruments, RSM subscales were correlated, but associations between IS were minimal.

Conclusions:

The present study provides initial support for the use of the RBS-R Caregiver and Self-Report to measure dimensions of RSM and IS behaviors in autistic adolescents and adults. The present data did not support the use of the ADI-R to assess these RRB subtypes in older individuals. Conclusions must be interpreted cautiously in light of the present study's sample limitations. Additional research is needed to understand differences in caregiver-reported and self-reported RRBs. Further research on RRBs in autistic adolescents and adults, particularly in samples with more gender and racial/ethnic diversity, is critical to inform community understanding and knowledge of autism in adulthood.

Lay summary

Why was this study done?

Restricted and repetitive behaviors (RRBs) are features necessary for the diagnosis of autism spectrum disorder and are assessed at all ages. It cannot be assumed, however, that instruments designed for assessing children are appropriate for use with older individuals. Therefore, we explored whether the Autism Diagnostic Interview-Revised (ADI-R) and the Repetitive Behavior Scale-Revised (RBS-R) questionnaire, instruments used to evaluate RRBs in children, can be used to assess adolescents and adults. This information is important to inform clinicians and researchers about the best ways to assess RRBs in older individuals.

What was the purpose of this study?

The purpose of this study was to determine if the ADI-R and RBS-R are appropriate to assess RRBs in autistic adults. Since RRBs are broad, we focused on how well these instruments measure two categories of RRBs: Repetitive Sensory Motor (RSM) and Insistence on Sameness (IS) behaviors. RSM includes behaviors such as hand flapping and lining up objects. IS includes behaviors such as negative responses to change and adherence to specific routines. Research supports the ADI-R and RBS-R for assessing these categories in children; however, little is known about their use in older samples. This study aimed to address this research gap.

What did the researchers do?

We used existing data from autistic adolescent and adults assessed using ADI-R, RBS-R Caregiver, or RBS-R Self-Report. We assessed the relationships between items on each instrument, whether items were meaningfully related to support categories of RSM and IS, and whether instrument subscales were related to age and nonverbal intelligence.

What were the results of the study?

Results provided support for use of the RBS-R Caregiver and Self-Report, but not the ADI-R, for assessing RSM and IS behaviors in adults. Scores on the RBS-R forms were not strongly related, suggesting that caregiver report and self-report may reflect different behaviors. This could be explained by caregivers not being aware of some behaviors their adult son or daughter exhibit. This would be consistent with previous research suggesting that autistic adults may hide or mask certain behaviors; however, this was not tested in this study.

What do these findings add to what was already known?

Findings demonstrate that the RBS-R Caregiver, commonly used to assess RRBs in children, can also be used to measure RSM and IS behaviors in autistic adolescents and adults. Results also provide initial evidence for the use of the RBS-R Self-Report to assess these behaviors in adults.

What are potential weaknesses in the study?

The sample was small and did not include equal representation of females and nonbinary identities, non-White or non-Hispanic ethnicities, individuals with intellectual disability, or older adults. Also, participants did not have data from all three instruments.

How will these findings help autistic adults now or in the future?

Findings inform clinicians and researchers about methods available to assess RRBs in adults. While further research is needed, especially in samples with more gender and racial/ethnic diversity, these results will contribute to more appropriate assessment of adults in clinical practice and research.