Effectiveness of the Integrated Psychotherapy Method in Major Depressive Disorder: A Retrospective Multiple-Case Single-Case Experimental Design Study

This study examined the effectiveness of the Integrated Psychotherapy Method (IPM) in the treatment of Major Depressive Disorder (MDD) using a retrospective multiple-case Single-Case Experimental Design (SCED). Five adults with moderate-to-severe depression completed standardized outcome measures reconstructed across three phases: baseline (A), initial intervention (B1), and consolidation (B2). Depressive symptoms (BDI-II), psychological distress (OQ-45.2), and quality of life (WHOQOL-BREF) were analyzed using Reliable Change Index (RCI), Tau-U effect sizes, percentage change, and confidence intervals. Qualitative idiographic analysis explored subjective and symbolic dimensions of change. Across cases, clinically meaningful reductions in depressive symptoms and psychological distress were observed, alongside improvements in psychological and social quality-of-life domains. RCI and Tau-U analyses indicated reliable and moderate-to-large treatment effects in most participants. Qualitative findings revealed a consistent pattern of change involving restoration of cognitive regulation, reconnection with emotional and relational life, emergence of symbolic meaning, and existential reintegration. Improvements at symptom and functional levels were accompanied by progressive reorganization of identity and autonomy. Findings provide preliminary evidence supporting IPM as a structured, process-oriented integrative approach for MDD, facilitating recursive psychological reorganization beyond symptom reduction. Although limited by its retrospective design and small sample, this study contributes idiographic evidence to a broader research program. Prospective investigations, including two planned randomized controlled trials on depression, are warranted to further evaluate the model’s efficacy and mechanisms of change.