Phase-based versus non-phase-based psychological interventions for complex PTSD: a systematic review and meta-analysis

Background: Since complex post-traumatic stress disorder (CPTSD) was incorporated to the International Classification of Diseases-11th revision (ICD-11), the construct has drawn increasing attention in clinical research due to its debilitating effects across multiple domains of functioning. However, whether stabilization (Phase 1) is necessary before exposure to traumatic memories (Phase 2) remains controversial.Objective: We examined whether phase-based interventions are more effective than non-phase-based interventions in reducing symptoms of CPTSD.Methods: On 17 June 2025, we searched the Cochrane Library, Embase, Medline, PTSDpubs, Scopus, and Web of Science as well as South Korean databases, including the Korean Citation Index, the Research Information Sharing Service, DataBase Periodical Information Academic (DBPia), and ScienceON. Randomized controlled trials of psychological interventions for individuals with clinically significant CPTSD symptoms or PTSD with at least two of the 'disturbances in self-organization' (DSO) symptom clusters were eligible. We used Hedges' g to pool effect sizes and performed subgroup analyses using Cochran's Q test. We assessed risk of bias using the Cochrane Risk-of-Bias Assessment 2 tool.Results: Across most outcomes, we observed no significant differences between phase- and non-phase-based interventions, between multi-phase and single-phase interventions, or between exposure and non-exposure interventions. However, multi-phase interventions had superior effects on PTSD, while phase-based, multi-phase, and exposure interventions showed greater improvements in DSO - affect regulation compared to their counterparts.Conclusions: This study was limited by the small number of available trials, single time-point, and heterogeneity in outcome measures, which constrained both the detection of subgroup differences and the precision of effect size estimates. Our findings provide empirical evidence for the current discourse, suggesting that non-phase-based and non-exposure-based interventions can be as effective as structured approaches in many contexts, while some outcomes may still benefit from phase-, multi-modular-, or exposure-based designs.