Explaining heterogeneity in disability associated with current major depressive disorder: Effects of illness characteristics and comorbid mental disorders

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Background Although major depressive disorder (MDD) is associated with disability, some persons do function well despite their illness. Aim of the present study was to examine the effect of illness characteristics and comorbid mental disorders on various aspects of disability among persons with a current MDD episode. Methods Data were derived from 607 participants with a current MDD based on the Composite International Diagnostic Interview (CIDI). Severity was assessed via the Inventory of Depressive Symptoms self-report (IDS-SR). For disability three outcome measures were used: World Health Organization Disability Assessment Schedule II (WHODAS) disability and its 7 dimensions, days out of role, and work absence. Using multiple regression analysis the effects of MDD characteristics and comorbid mental disorders were estimated. Results The IDS-SR score was the best predictor of all disability outcomes. Of the comorbid mental disorders, agoraphobia was significantly associated with overall disability. Collectively, all illness characteristics accounted for 43% of variance in WHODAS disability, 13% in days out of role and 10% in work absence, suggesting substantial unexplained variance. Limitations Only self-report measures of disability were used. There were no assessments of other diagnoses than depressive, anxiety and alcohol use disorders. Conclusions Although heterogeneity in disability of persons with current MDD is partially explained by illness characteristics of MDD (especially symptom severity) and comorbid mental disorders, most of the variance is not accounted for.