BackgroundThe efficacy of the unified protocol of the transdiagnostic treatment for emotional disorders (UP) has been poorly studied in patients with depressive disorders. This study aimed to examine the efficacy of UP for improving depressive symptoms in patients with depressive and/or anxiety-related disorders.MethodsThis assessor-blinded, randomized, 20-week, parallel-group, superiority study compared the efficacy of the UP with treatment-as-usual (UP-TAU)v.wait-list with treatment-as-usual (WL-TAU). Patients diagnosed with depressive and/or anxiety disorders and with depressive symptoms participated. The primary outcome was depressive symptoms assessed by GRID-Hamilton depression rating scale (GRID-HAMD) at 21 weeks. The secondary outcomes included assessor-rated anxiety symptoms, severity and improvement of clinical global impression, responder and remission status, and loss of principal diagnosis.ResultsIn total, 104 patients participated and were subjected to intention-to-treat analysis [mean age = 37.4,s.d.= 11.5, 63 female (61%), 54 (51.9%) with a principal diagnosis of depressive disorders]. The mean GRID-HAMD scores in the UP-TAU and WL-TAU groups were 16.15 (s.d.= 4.90) and 17.06 (s.d.= 6.46) at baseline and 12.14 (s.d.= 5.47) and 17.34 (s.d.= 5.78) at 21 weeks, with a significant adjusted mean change difference of −3.99 (95% CI −6.10 to −1.87). Patients in the UP-TAU group showed significant superiority in anxiety and clinical global impressions. The improvement in the UP-TAU group was maintained in all outcomes at 43 weeks. No serious adverse events were observed in the UP-TAU group.ConclusionsThe UP is an effective approach for patients with depressive and/or anxiety disorders.