PURPOSE: To assess and compare the levels of functioning in patients with major depressive disorder treated with either duloxetine with a daily dose of ≤60 mg or a selective serotonin reuptake inhibitor (SSRI) as monotherapy for up to 6 months in a naturalistic setting in East Asia. In addition, this study examined the impact of painful physical symptoms (PPS) on the effects of these treatments. PATIENTS AND METHODS: Data for this post hoc analysis were taken from a 6-month prospective observational study involving 1,549 patients with major depressive disorder without sexual dysfunction. The present analysis focused on a subgroup of patients from East Asia (n=587). Functioning was measured using the Sheehan Disability Scale (SDS). Depression severity was assessed using the 16-item Quick Inventory of Depressive Symptomatology-Self Report. PPS were rated using the modified Somatic Symptom Inventory. A mixed model with repeated measures was fitted to compare the levels of functioning between duloxetine-treated (n=227) and SSRI-treated (n=225) patients, adjusting for baseline patient characteristics. RESULTS: The mean SDS total score was similar between the two treatment cohorts (15.46 [standard deviation =6.11] in the duloxetine cohort and 16.36 [standard deviation =6.53] in the SSRI cohort, P=0.077) at baseline. Both descriptive and regression analyses confirmed improvement in functioning in both groups during follow-up, but duloxetine-treated patients achieved better functioning. At 24 weeks, the estimated mean SDS total score was 4.48 (standard error =0.80) in the duloxetine cohort, which was statistically significantly lower (ie, better functioning) than that of 6.76 (standard error =0.77) in the SSRI cohort (P<0.001). This treatment difference was more apparent in the subgroup of patients with PPS at baseline. Similar patterns were also observed for SDS subscores (work, social life, and family life). CONCLUSION: Depressed patients treated with duloxetine achieved better functioning compared to those treated with SSRIs. This treatment difference was mostly driven by patients with PPS at baseline.