Validation of the 12-item World Health Organization Disability Assessment Schedule (WHODAS 2.0) in adults with attention-deficit hyperactivity disorder

Background Attention deficit hyperactivity disorder (ADHD) is often associated with psychosocial functioning difficulties and valid measures of disability are needed for this population. The 12-item World Health Organization Disability Assessment Schedule 2.0 (WHODAS 2.0) is widely used to measure disability but has not been validated in the adult ADHD population. Aims This study aims to assess the psychometric properties of the WHODAS 2.0 in adults with ADHD, and to examine differences in disability levels between ADHD subtypes and gender. Method A cross-sectional study was conducted with 577 adults with ADHD (mean age: 38.24, s.d = 12.23; 52.3% male). ADHD severity was assessed using the ADHD Rating Scale (ADHD-RS) and Clinical Global Impression-Severity (CGI-S) Scale, while functionality was measured with the WHODAS 2.0 and the Functioning Assessment Short Test (FAST). Analyses included: (a) Cronbach's α for internal consistency, (b) Pearson's correlation for convergent validity, (c) Confirmatory Factor Analysis (CFA) for factor structure and (d) t-tests to compare disability levels across ADHD subtypes and gender. Results The WHODAS 2.0 demonstrated good internal consistency (Cronbach's α = 0.89). Scores were significantly correlated with psychosocial functioning (FAST, r = 0.476, p < 0.001) and clinical measures. CFA supported the original six-factor structure (root mean square error of approximation 0.039, Comparative Fit Index 0.998, Tucker-Lewis Index 0.996). When comparing ADHD subtypes, participants with the combined subtype had higher WHODAS 2.0 total scores than those with the inattentive subtype (p = 0.006). Additionally, gender differences were identified, with females displaying higher disability levels (p = 0.005). Conclusions The WHODAS 2.0 demonstrates psychometric properties that suggest it is a valid and reliable tool for assessing disability in adults with ADHD.