Group-Based Interventions for Posttraumatic Stress Disorder: A Systematic Review and Meta-Analysis of the Role of Trauma Type.

Background: Post-traumatic stress disorder (PTSD) is associated with poor health outcomes. While group-based therapies offer accessible treatment options, their effectiveness remains unclear. Social identity factors, such as shared group membership and stigma, may influence treatment success. Objectives: This review examined: (1) the effectiveness of group-based treatments for PTSD symptoms, (2) differences between group and individual therapies, (3) whether trauma type (e.g., interpersonal, stigmatized) and group fit (e.g., gender, shared trauma) moderate outcomes, and (4) the role of group and social identity factors in existing research. Search Methods: A systematic search (April 2023, re-run May 2025) identified quantitative studies of group therapies (≥3 participants, ≥5 sessions) addressing PTSD symptoms, compared to individual or control conditions. Forty studies met criteria (23 RCTs, 17 non-RCTs) from an initial pool of 8,256 records. Interventions included group CBT, counselling, psychodynamic, and other approaches. Selection Criteria: A variety of group-based treatments were eligible for inclusion, such as group-based CBT, CPT, and alternative group treatments. In line with previous research, protocols had to include a minimum of three individuals per group and meet for at least five sessions. Interventions assessed PTSD symptoms pre-intervention and post-intervention using a valid and reliable measure. Data Collection and Analysis: Primary outcome data was collected using valid measures of PTSD (e.g. CAPS, PCL). Effect sizes were computed for outcomes within each study. Where a study provided more than one effect size for each outcome, we accounted for this in statistical analyses. Main Results: Across 40 studies in 11 countries, most involving women or mixed-gender groups, trauma types varied, with combat-related PTSD most common ( Authors’ Conclusions: Group-based interventions reduce PTSD symptoms. Larger effects were observed for certain group characteristics, such as participant age, group size, gender, and shared experiences; however, findings are exploratory and should be interpreted with caution. Some limitations should also be considered. The majority of included studies had some concerns or were at moderate risk of bias, there was unexplained heterogeneity between studies, as well as evidence of possible publication bias. However, sensitivity analyses excluding studies at high or serious risk of bias yielded similar findings. Future research should build on existing evidence to examine how social identity processes influence the effectiveness of group-based interventions for PTSD across diverse populations and formats.