Trazodone effectiveness in depression (TED): a comparative evaluation of effect sizes trazodone extended release and SSRIs in the treatment of major depressive disorder

Introduction: Major depressive disorder (MDD) constitutes a significant global mental health concern. Although selective serotonin reuptake inhibitors (SSRIs) are first-line treatment, their effectiveness may be limited by adverse effects including anhedonia, emotional blunting, sleep disturbances, and sexual dysfunction. Trazodone, a serotonin antagonist and reuptake inhibitor, offers a more favorable tolerability profile, particularly in its extended-release (XR) formulation. Previous studies within the trazodone effectiveness in depression (TED) project demonstrated more pronounced improvements with trazodone XR compared to SSRIs in reducing depressive, anxiety, and insomnia symptoms. The present analysis extends these findings by comparing trazodone XR with SSRIs and quantifying the extent and clinical importance of treatment outcomes through effect size estimates. Methods: This single-center, non-randomized, open-label, 12-week naturalistic study-conducted as part of the TED project-included adults aged 18-65 diagnosed with MDD. Symptom severity and outcomes were assessed at baseline and weeks 2, 4, 8, and 12 using validated clinician- and self-rated scales. Cohen's d quantified the magnitude and clinical relevance of differences between trazodone XR and SSRIs. Results: Effect-size analyses demonstrated consistently greater and earlier improvements with trazodone XR versus SSRIs across all measures. In both self-rated (QIDS-SR) and clinician-rated (QIDS-CR; MADRS) scales assessing depressive symptoms, trazodone XR showed larger effect sizes from week 4, with further increases through week 12. Similar patterns were observed for anhedonia (SHAPS), anxiety (HAM-A) and insomnia (AIS), where trazodone XR produced greater and progressively increasing effect sizes, while SSRIs reached a plateau. These findings indicate a more robust and sustained therapeutic impact of trazodone XR, reflected by consistently higher effect-size magnitudes across domains. Discussion: Trazodone XR demonstrated greater and progressively increasing effect sizes compared with SSRIs, indicating a more sustained antidepressant response over 12 weeks. This trajectory, marked by continued symptom reduction without a linear response pattern, suggests a cumulative therapeutic effect potentially attributable to trazodone's multimodal serotonergic mechanism and favorable pharmacokinetics. By concurrently addressing mood, anxiety, and sleep-related domains, trazodone XR appears to facilitate both symptomatic improvement and broader functional stabilization. These findings highlight the need for randomized, controlled investigations to further elucidate its comparative efficacy and real-world relevance.