The 12-item WHO Disability Assessment Schedule II as an outcome measure for treatment of common mental disorders

Background. Common mental disorders (CMD) are among the most significant contributors to disability worldwide. Patient-reported disability outcomes should be included as a key metric in the comparative assessment of value across global mental health interventions. This study aims to evaluate the validity of a widely used, cross-cultural tool - the 12-item World Health Organization Disability Assessment Schedule II (WHODAS) - as a functional outcome measure for CMD treatment. Methods. The study population includes 1024 participants with CMD enrolled in the MANAS trial in India. CMD was assessed using the Revised Clinical Interview Schedule (CIS-R). Disability was assessed using the 12-item WHODAS II plus a measure of disability days. This analysis presents the correlations between these disability items and CMD symptom severity at 2 months after enrollment (convergent validity) and the items' associations with CMD recovery 4 months later (external responsiveness). Results. All items showed a positive correlation of disability with CMD symptom severity (p < 0.001). The WHODAS items of 'standing,' 'household responsibilities,' and 'emotional disturbance' explained the most variance in CMD symptom severity. Improvements in 'disability days,' 'emotional disturbance,' 'standing,' 'household responsibilities,' 'day-to-day work,' and 'concentrating' were significantly associated with CMD recovery over follow-up. Conclusions. Further research is recommended on a CMD-specific WHODAS subscale comprised of the six WHODAS items found to be most strongly associated with CMD severity and recovery. This shorter, CMD-specific disability subscale would critically serve as a common metric to compare intervention impact on patient-centered outcomes and, in turn, to allocate global mental health resources efficiently.