Intellectual disabilities moderate sex/gender differences in autism spectrum disorder: a systematic review and meta-analysis.
Intellectual disability reverses the usual sex pattern in autism—girls with ID present the more severe profile.
01Research in Context
What this study did
Emerson et al. (2023) pooled every paper they could find on sex differences in autism. They only kept studies that also said whether kids had intellectual disability (ID). Then they ran a meta-analysis to see if ID changed the boy-girl gap.
The review looked at three symptom areas: social skills, restricted and repetitive behaviors (RRBIs), and language. Each study was split into two groups: kids with ID and kids without ID.
What they found
ID flips the sex pattern. Girls without ID have milder RRBIs and better language than boys without ID. Girls with ID show more social, RRBI, and motor problems than boys with ID.
In plain words: once ID enters the picture, girls look more severe, not less.
How this fits with other research
Wormald et al. (2019) found no sex differences on the SRS-2 in high-functioning kids. Emerson et al. (2023) explains why: those kids mostly had no ID, the very group where sex gaps shrink.
Souza et al. (2023) also saw girls with ID pile up more RRBIs and epilepsy. The new meta-analysis backs that observation with harder numbers.
Blair et al. (2020) told clinicians to watch for sex bias; Emerson et al. (2023) gives the concrete rule—always note ID status before you compare boys and girls.
Why it matters
If you test a girl with ASD plus ID, do not expect the "typical" female profile of milder symptoms. She may need stronger intervention in social, play, and self-care domains than a boy of the same IQ. Update your intake forms: add an ID checkbox and adjust your expectations when it is ticked.
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02At a glance
03Original abstract
BACKGROUND: Girls/women with autism spectrum disorder (ASD) are suggested to exhibit different symptom profiles than boys/men with ASD. Accumulating evidence suggests that intellectual disability (ID) may affect sex/gender differences in ASD. However, a systematic review and meta-analysis on this topic is missing. METHODS: Two databases (MEDLINE and PsycINFO) were used to search for studies reporting sex/gender differences (girls/women versus boys/men) in social communication and interaction, restrictive and repetitive behaviour and interests (RRBIs), sensory processing, and linguistic and motor abilities in ASD. The final sample consisted of 79 studies. The meta-analysis was performed with Review Manager using a random-effects model. Participants with ASD without and with ID were analysed as separate subgroups, and the effects in these two subgroups were also compared with each other. RESULTS: Girls/women with ASD without ID displayed fewer RRBIs, more sensory symptoms and less problems in linguistic abilities than their boys/men counterparts. In contrast, girls/women with ASD with ID displayed more social difficulties and RRBIs, poorer linguistic abilities and more motor problems than boys/men with ASD with ID. Comparisons of groups of participants with ASD without ID versus participants with ASD with ID confirmed differences in sex/gender effects on social difficulties, sensory processing, linguistic abilities and motor abilities. CONCLUSIONS: Our results clearly suggest that the female phenotype of ASD is moderated by ID. Among individuals with ASD with ID, girls/women seem to be more severely affected than boys/men, whereas among individuals with ASD without ID, girls/women with ASD may have less symptoms than boys/men. Such phenotypic differences could be a potential cause of underrecognition of girls/women with ASD, and it is also possible that observed phenotypic differences may reflect underdiagnosing of girls/women with ASD.
Journal of intellectual disability research : JIDR, 2023 · doi:10.1111/jir.12989