Autism Severity and Disability: A Cross-sectional Study Using the ISAA and WHODAS 2.0

Background: Adults with autism spectrum disorder (ASD) show wide variation in daily functioning. Disability assessment in practice often relies on measures of symptom severity, although the extent to which symptom severity reflects functional disability in adulthood remains unclear. We examined the association between autism symptom severity and functional disability in adults with ASD using the Indian Scale for Assessment of Autism (ISAA) and the World Health Organization Disability Assessment Schedule 2.0 (WHODAS 2.0). Methods: This cross-sectional study included 78 adults with ASD recruited from clinical and community-based service settings. Autism symptom severity and functional disability were assessed using ISAA and WHODAS 2.0, respectively. Associations were examined using Spearman’s correlation and multivariable linear regression, adjusting for age and co-occurring intellectual and developmental disability. Results: ISAA total scores strongly correlated with WHODAS 2.0 scores (ρ = 0.83, p < .001). WHODAS scores increased across ISAA severity categories (19.22 ± 8.74 vs. 36.53 ± 10.74 vs. 52.29 ± 8.03; p < .001). In multiple regression analysis, autism severity (B = 0.46, p < .001) and co-occurring intellectual disability (B = 6.55, p = .017) remained significant independent predictors of functional disability, explaining 69.6% of the variance (adjusted R 2 = 0.696). Conclusion: Autism severity was strongly associated with functional disability in adulthood; however, it did not fully account for real-world functioning. These findings underscore the multidimensional nature of disability and support the need for incorporating broader, function-focused assessment tools in adult disability evaluation.