Academic Skills in Students with Autism Spectrum Disorder and Intellectual Disability: A Systematic Review and Meta-Analysis

Background: A substantial proportion of children with autism spectrum disorder (ASD) also have an intellectual disability (ID). However, the academic achievement levels of students with ASD and ID (ASD-ID) are poorly documented and known. Method: We systematically reviewed studies on school skills (reading, spelling, and math) in children and adolescents with ASD-ID. The search was conducted in seven bibliographic databases: Embase, Pubmed/MEDLINE, PsycINFO, Cochrane Library, Ebscohost, Proquest, and Scopus until 28 May 2022. Results: We identified 33,750 reports, four of which met the inclusion criteria for the review. The studies, characterized by Level III evidence (non-randomized controlled trials), included 535 students, 266 in the ASD-ID group and 269 in the ASD-no ID group. A random-effects model meta-analysis revealed that students with ASD-ID had significantly lower reading, spelling, and math scores than students with ASD-no ID. The effect sizes associated with reading score differences were large, although with significant heterogeneity; similarly, the effect sizes associated with spelling and math score differences were also large, although to a lesser extent than for reading. Conclusions: The co-presence of ASD and ID is associated with significant deficits in reading, spelling, and math. However, the present meta-analytic results rest on a limited number of studies. This contrasts with the substantial proportion of children with ASD who have ID and highlights the need for further research to fill a significant gap regarding the profile of academic abilities of students with ASD-ID.