Psychometric properties of the World Health Organization Disability Assessment Schedule used in the European Study of the Epidemiology of Mental Disorders

Abstract

This study assessed the factor structure, internal consistency, and discriminatory validity of the World Health Organization Disability Assessment Schedule (WHODAS) version used in the European Study of the Epidemiology of Mental Disorders (ESEMeD). In total 8796 adults were assessed using the ESEMeD WHODAS (22 severity and 8 frequency items). An Exploratory Factor Analysis (EFA) with promax rotation was done with a random 50%. The other half was used for confirmatory factor analysis (CFA) comparing models (a) suggested by EFA; (b) hypothesized a priori; and (c) reduced with four items. A CFA model with covariates was conducted in the whole sample to assess invariance across Mediterranean (Spain, France and Italy) and non-Mediterranean (Belgium, Germany and the Netherlands) countries. Cronbach's alphas and discriminatory validity were also examined. EFA identified seven factors (explained variance: 80%). The reduced model (six factors, four frequency items excluded) presented the best fit [Confirmatory Fit Index (CFI) = 0.992, Tucker-Lewis Index (TLI) = 0.996, Root Mean Square Error of Approximation (RMSEA) = 0.024]. The second-order factor structure also fitted well (CFI = 0.987, TLI = 0.991, RMSEA = 0.036). Measurement non-invariance was found for Embarrassment. Cronbach's alphas ranged from 0.84 for Participation to 0.93 for Mobility. Preliminary data suggest acceptable discriminatory validity. Thus, the ESEMeD WHODAS may well be a valuable shortened version of the WHODAS-II, but future users should reconsider the filter questions.