Restricted and repetitive behaviors and interests (RRBIs) are core features ofautism spectrum disorder. They include stereotyped movements, rigid routines,fixated interests, and differences in sensory responses.
Recent research suggests that RRBIs may manifest differently between autistic males and females. For instance, males might show more obvious repetitive behaviors or interests in mechanical objects, while females may have more socially-oriented or camouflaged RRBIs.
Studying these sex differences is crucial for several reasons: it can improve diagnostic accuracy, especially forfemales who are often underdiagnosed; it can lead to more tailored interventions and support strategies; and it deepens our understanding of autism’s diverse presentations.
This knowledge is vital for creating more inclusivediagnostic criteriaand ensuring that all autistic individuals receive appropriate recognition and support.
Key Points
Rationale
The rationale for this study was to address gaps in the existing literature on sex differences in restricted and repetitive behaviors and interests (RRBIs) in autism.
Previous research and reviews have typically focused on broad constructs ofautism symptomatology, including RRBIs as an overall domain (van Wijngaarden-Cremers et al., 2014).
However, there was a lack of systematic examination of sex differences at the level of narrow RRBI constructs based on the DSM-5 diagnostic criteria.
The authors note that consistently exploring sex differences only at the broad construct level may miss potential subtle differences in specific RRBI subdomains.
This is particularly important given emerging evidence of a potential “Female Autism Phenotype” that may manifest differently from traditional (male-centric) conceptualizations of autism (Hull et al., 2020).
Understanding nuanced sex differences in RRBIs could help explain the underdiagnosis of autism in females.
Additionally, while previous reviews had found that autistic females generally display fewer RRBIs than males at the broad construct level (Lai et al., 2015; van Wijngaarden-Cremers et al., 2014), studies examining narrow RRBI constructs produced more mixed results.
For example, some research found no sex differences in specific RRBI behaviors like stereotyped language or resistance to change (Mclennan et al., 1993), while others reported higher rates of sensory issues in autistic females (Lai et al., 2011).
Overall, a fine-grained analysis of sex differences across narrow RRBI constructs was needed to clarify inconsistencies in the literature and potentially inform more sensitive diagnostic approaches.
Method
The study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.
The review protocol was prospectively registered on PROSPERO (registration number: CRD42021254221).
Search strategy and terms
The authors searched six electronic databases on May 25, 2021: APA PsychInfo, Medline, ERIC, Science Direct, PsycArticles, and CINAHL Plus with Full Text.
Search terms were based on DSM-5 autism symptom subdomains of restricted, repetitive patterns of behavior, interests, or activities.
Population terms included “autism spectrum disorder” and “autism spectrum condition”. Comparator terms were “sex” and “gender”.
Outcome terms included “repetitive behavi?r*”, “restricted interest”, “insistence on sameness”, “sensory”, and “circumscribed interest*”.
The full search strategy is provided in the supplementary materials. Reference lists of included studies were also hand-searched.
The search was re-run on October 21, 2022 to identify any additional relevant articles.
Inclusion and exclusion criteria:
Inclusion criteria:
Exclusion criteria:
The authors provide a detailed rationale for the inclusion/exclusion criteria in Table 1 of the paper.
Statistical measures
Four random-effects meta-analyses were performed using Comprehensive Meta-Analysis software, one for each narrow RRBI construct.
Standardized mean differences (SMD) were calculated between autistic males and females. Where studies used multiple measures, the measure most closely reflecting the narrow construct was selected.
Publication bias was assessed through visual inspection of funnel plots and Egger’s test. Heterogeneity was evaluated using chi-squared tests and the I2 statistic.
The authors planned moderator analyses for age groups and IQ levels, but were unable to conduct these due to limitations in the included studies.
A post-hoc sensitivity analysis of high-quality studies and a meta-regression with publication year as a covariate were conducted.
Results
The systematic review included 46 studies in the narrative synthesis, with 25 of these included in the meta-analyses.
Key findings for each RRBI subdomain were:
Stereotyped or repetitive motor movements, use of objects, or speech:
Highly restricted, fixated interests that are abnormal in intensity or focus:
Insistence on sameness, inflexible adherence to routines, or ritualized patterns of verbal/nonverbal behavior:
Hyper- or hypo-reactivity to sensory input or unusual interests in sensory aspects of the environment:
Heterogeneity and publication bias:
The authors were unable to conduct planned moderator analyses for age and IQ due to limitations in the included studies.
A sensitivity analysis of high-quality studies produced similar results to the main analyses.
Insight
This systematic review and meta-analysis provides important insights into sex differences in restricted and repetitive behaviors and interests (RRBIs) in autism.
By examining narrow constructs of RRBIs rather than broad domains, the study reveals a more nuanced picture of how these core autism features may manifest differently in males and females.
The finding that autistic males display higher rates of stereotyped behaviors and restricted interests compared to females is particularly informative.
This aligns with and extends previous research suggesting fewer overall RRBIs in autistic females (van Wijngaarden-Cremers et al., 2014).
The qualitative differences in restricted interests between males and females provide crucial insight into potential biases in autism identification and diagnosis.
The tendency for autistic females to have more socially-oriented or developmentally normative interests (e.g. animals, relationships) compared to the object-focused interests often associated with male autism presentations (e.g. mechanics, transportation) could contribute to females being overlooked for autism assessment.
The lack of significant sex differences in sensory experiences and insistence on sameness is also informative, suggesting these features may be equally prevalent in autistic males and females.
This highlights the importance of thoroughly assessing these domains in all individuals, regardless of sex.
They underscore the need for more sensitive, sex-informed approaches to autism assessment and diagnosis.
Future research should further explore how these RRBI differences manifest across development and in individuals without formal autism diagnoses.
Additionally, investigating the underlying neurobiological and sociocultural factors contributing to these sex differences would be valuable.
Strengths
The study had several methodological strengths:
Limitations
Several limitations should be considered when interpreting the results:
These limitations highlight the need for future research with more representative samples, longitudinal designs, and consideration of potential moderating factors like age and cognitive ability.
Clinical Implications
The findings of this study have significant implications for autism research, clinical practice, and diagnostic processes:
These implications collectively point to the need for a more individualized, sex-informed approach to autism assessment, diagnosis, and support that considers the diverse ways in which core features like RRBIs may manifest across different populations.
References
Primary reference
Edwards, H., Wright, S., Sargeant, C., Cortese, S., & Wood‐Downie, H. (2024). Research review: A systematic review and meta‐analysis of sex differences in narrow constructs of restricted and repetitive behaviours and interests in autistic children, adolescents, and adults.Journal of Child Psychology and Psychiatry,65(1), 4-17.https://doi.org/10.1111/jcpp.13855
Other references
Bargiela, S., Steward, R., & Mandy, W. (2016). The experiences of late-diagnosed women with autism spectrum conditions: An investigation of the female autism phenotype. Journal of Autism and Developmental Disorders, 46(10), 3281-3294.
Hull, L., Petrides, K. V., & Mandy, W. (2020). The female autism phenotype and camouflaging: A narrative review. Review Journal of Autism and Developmental Disorders, 7(4), 306-317.
Lai, M. C., Lombardo, M. V., Pasco, G., Ruigrok, A. N., Wheelwright, S. J., Sadek, S. A., … & Baron-Cohen, S. (2011). A behavioral comparison of male and female adults with high functioning autism spectrum conditions. PloS one, 6(6), e20835.
Lai, M. C., Lombardo, M. V., Auyeung, B., Chakrabarti, B., & Baron-Cohen, S. (2015). Sex/gender differences and autism: setting the scene for future research. Journal of the American Academy of Child & Adolescent Psychiatry, 54(1), 11-24.
Mclennan, J. D., Lord, C., & Schopler, E. (1993). Sex differences in higher functioning people with autism. Journal of autism and developmental disorders, 23(2), 217-227.
van Wijngaarden-Cremers, P. J., van Eeten, E., Groen, W. B., Van Deurzen, P. A., Oosterling, I. J., & Van der Gaag, R. J. (2014). Gender and age differences in the core triad of impairments in autism spectrum disorders: a systematic review and meta-analysis. Journal of autism and developmental disorders, 44(3), 627-635.
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Saul McLeod, PhD
BSc (Hons) Psychology, MRes, PhD, University of Manchester
Saul McLeod, PhD., is a qualified psychology teacher with over 18 years of experience in further and higher education. He has been published in peer-reviewed journals, including the Journal of Clinical Psychology.
Olivia Guy-Evans, MSc
BSc (Hons) Psychology, MSc Psychology of Education
Olivia Guy-Evans is a writer and associate editor for Simply Psychology. She has previously worked in healthcare and educational sectors.
