Measurement invariance of the 12-item self-administered World Health Organization Disability Assessment Schedule (WHODAS) 2.0 across early and late adolescents in Canada

Purpose This study examined whether the 12-item self-administered World Health Organization Disability Assessment Schedule (WHODAS) 2.0 demonstrated measurement invariance between young adolescents aged 10-16 years with a physical illness and older adolescents aged 15-19 years from the general population. Materials and methods Young adolescent data come from the baseline wave of the Multimorbidity in Youth across the Life-course study (n = 117) and older adolescent data come from the Canadian Community Health Survey-Mental Health (n = 1851). Multiple-group confirmatory factor analysis was used to test measurement invariance. WHODAS 2.0 scores were compared across morbidity subgroups using multiple regression. Results Measurement invariance of the WHODAS 2.0 was demonstrated: (chi(2)=635.2(144), p<.001; RMSEA = 0.059 (0.054, 0.064); CFI = 0.967; TLI = 0.970; and, SRMR = 0.068). Adjusting for data source, sex, race, immigrant status, and household income, WHODAS 2.0 scores were associated with morbidity status in a dose-response manner: physical illness only (B = 1.50, p<.001), mental illness only (B = 2.92, p<.001), and physical-mental comorbidity (B = 4.44, p<.001). Conclusions Measurement invariance of the WHODAS 2.0 suggests that young adolescents interpret the items and disability construct similarly to older adolescents - a group that previously demonstrated measurement invariance with an adult sample. The 12-item self-administered WHODAS 2.0 may be used to measure disability across the life-course.