Alexithymia in neurodevelopmental populations: a scoping review of Down syndrome, autism spectrum disorder, and dual diagnosis.

Background: Alexithymia, characterized by difficulties in identifying and describing emotions, affects ~10% of the general population. Prevalence is substantially higher in individuals with neurodevelopmental disorders. Objective: To systematically map existing research on alexithymia across Down syndrome, autism spectrum disorder, and dual diagnosis populations, synthesize current knowledge, and identify critical research gaps informing future investigation priorities. Methods: Following Arksey and O'Malley's framework and PRISMA-ScR guidelines, searches were conducted across MEDLINE, PsycINFO, EMBASE, CINAHL, and Cochrane databases from inception to December 2024. Studies examining alexithymia, emotional processing, or emotional awareness in DS, ASD, or DS-ASD populations underwent selection and narrative synthesis employing thematic analysis. Results: Database searches yielded 2,847 records, of which 55 studies met inclusion criteria spanning 1994-2024. Literature demonstrates research imbalances, with extensive evidence on ASD contrasted with minimal investigation on DS and the absence of research on dual diagnoses. Six major themes emerged: prevalence disparities with ASD populations showing 49.9% weighted mean prevalence vs. unestablished DS rates; assessment limitations with current tools lacking intellectual disability validation; intervention approaches demonstrating moderate effectiveness ( Conclusion: Current evidence reveals research imbalances with extensive ASD literature contrasting with the absence of DS research, limiting understanding and evidence-based practice. The lack of dual diagnosis investigation represents a gap affecting 16-18% of individuals with DS. Priorities include developing assessment methodologies for intellectual disability populations, establishing DS alexithymia prevalence, and investigating population-specific intervention approaches to optimize therapeutic outcomes and quality of life across the neurodevelopmental spectrum. Systematic review registration: https://doi.org/10.17605/OSF.IO/K8UEC, identifier: OSF.IO/K8UEC.