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.

BACKGROUND: Evidence that autism often manifests differently between males and females is growing, particularly in terms of social interaction and communication, but it is unclear if there are sex differences in restricted and repetitive behaviours and interests (RRBIs) when rigorously focusing on the narrow construct level (i.e., stereotyped behaviour, restricted interests, insistence on sameness, and/or sensory experiences). METHODS: We conducted a systematic review and four random effects meta-analyses investigating sex differences in narrow construct measures of RRBIs in autistic children, adolescents, and adults (Prospero registration ID: CRD42021254221). Study quality was appraised using the Newcastle-Ottawa Quality Assessment Scale. RESULTS: Forty-six studies were narratively synthesised and 25 of these were included in four random effects meta-analyses. Results found that autistic males had significantly higher levels of stereotyped behaviours (SMD = 0.21, 95% confidence interval (CI) [0.09, 0.33], p < .001) and restricted interests (SMD = 0.18, 95% CI [0.07, 0.29], p < .001) compared to autistic females. In contrast, there were no significant sex differences for sensory experiences (SMD = -0.09, 95% CI [-0.27, 0.09], p = .32) and insistence on sameness (SMD = 0.01, 95% CI [-0.03, 0.05], p = .68). The findings from the narrative synthesis were generally consistent with those from the meta-analyses and also found qualitative sex differences in the way RRBIs manifest. CONCLUSIONS: Our findings show significant differences in narrowly defined RRBIs in males and females. Practitioners need to be aware of such differences, which could be contributing to the under-recognition of autism in females and may not be captured by current diagnostic instruments.

Sex/Gender Differences in Camouflaging in Children and Adolescents with Autism.

This study investigated sex/gender differences in camouflaging with children and adolescents (N = 84) with and without an autism diagnosis/increased levels of autistic traits using two conceptualisations/operationalisations of camouflaging. A significant group-by-gender interaction using ANCOVA, with the covariate of verbal IQ, reflected similar levels of social reciprocity in autistic and neurotypical females, whereas autistic males had lower reciprocity than neurotypical males. Autistic females also had higher reciprocity than autistic males, despite similar levels of autistic traits (behavioural camouflaging). Additionally, autistic males and females had similar theory of mind skills, despite females having increased reciprocity (compensatory camouflaging). These findings provide evidence of increased camouflaging in autistic females, which may contribute to delay in the recognition of difficulties and provision of support.

Research Review: A systematic review and meta-analysis of sex/gender differences in social interaction and communication in autistic and nonautistic children and adolescents.

BACKGROUND: Evidence increasingly suggests that ASD manifests differently in females than males. Previous reviews investigating sex/gender differences in social interaction and social communication have focused at the level of broad constructs (e.g. comparing algorithm scores from pre-existing diagnostic instruments) and have typically reported no significant differences between males and females. However, a number of individual studies have found sex/gender differences in narrow construct domains. METHODS: We conducted a systematic review and random effects model meta-analyses (in January 2019 and updated January 2020) that investigated sex/gender differences in narrow construct measures of social communication and interaction in autistic and nonautistic children and adolescents, and adults. Study quality was appraised using the Appraisal Tool for Cross-Sectional Studies (AXIS, BMJ Open, 6, 2016, 1). RESULTS: Across 16 studies (including 2,730 participants), the analysis found that female (vs. male) individuals with ASD had significantly better social interaction and social communication skills (SMD = 0.39, p < .001), which was reflective of a similar sex/gender profile in nonautistic individuals (SMD = 0.35, p < .001). Nonautistic males had significantly better social interaction and communication than males with ASD (SMD = 0.77, p < .001). Nonautistic females also had significantly better social interaction and communication than females with ASD (SMD = 0.72, p  <.001). Nonautistic males had better social interaction and communication than females with ASD, though this difference was not significant (SMD = 0.30, p = .07). CONCLUSIONS: This systematic review and meta-analysis highlighted important sex/gender differences in social interaction and communication for individuals with ASD, likely not captured by pre-existing diagnostic instruments, which potentially contribute to the under recognition of autism in females, and may need to be reflected in the diagnostic process.