Another Foundation-Funded Study Published: Randomized Controlled Trial on the Effects of the IFS-Focused Program for Alleviating and Resolving Trauma and Stress (PARTS)

Details: Created: Tuesday, 03 February 2026 20:20

Another Foundation-Funded Study Published:
Randomized Controlled Trial on the Effects
of the IFS-Focused Program for Alleviating and Resolving Trauma and Stress (PARTS)

The Foundation for Self Leadership is pleased to announce that the Center for Mindfulness and Compassion at Cambridge Health Alliance, affiliated with Harvard Medical School, has published the results of a Randomized Controlled Trial (RCT) to test the effects of Internal Family Systems Therapy's clinical protocol in treating complex PTSD.

The outcomes of the rigorous study, named Program for Alleviating and Resolving Trauma and Stress (PARTS), which followed an earlier feasibility assessment of group and online therapy (both funded by the Foundation), now appear in the American Psychological Association's journal Psychological Trauma: Therapy, Research, Practice, and Policy.

"The Foundation, a nonprofit dedicated to IFS-related research and advocacy pursuing a vision to foster deeper healing and wellbeing in our world, operates at an arms-length from the studies it supports," stated Toufic Hakim, PhD, Executive Director. "We are pleased to see yet another rigorous study in the public scientific domain," he continued. "It is critical for us to emphasize that, while our goal is to expand the base of empirical evidence, we follow where the science leads and never get ahead of it."

The Foundation does all it can to catalyze research and has been investing in a research fellowship to grow the network of competent researchers interested in examining the efficacy of clinical IFS.

Study Methodology and Comparative Results

PARTS is a 16-week group-based PTSD treatment program derived from the IFS theoretical framework. The now-published pilot RCT study randomized a total of 60 patients with PTSD either to the PARTS intervention or an active control arm called Nature-Based Stress Reduction for Trauma Survivors (NBSR-T), with 30 patients in each treatment arm. The published results show that patients in the PARTS arm attended 12.8 out of the total of 16 group sessions, which was significantly more than the average of 10 sessions attended by the NBSR-T treatment arm. Patients in the PARTS treatment arm also reported higher levels of group satisfaction than the control arm. Both treatment arms showed statistically significant large reductions in PTSD symptoms (measured by the gold standard clinician-administered CAPS-5 PTSD assessment) without significant differences between the two treatment arms. Notably, the large effect size reductions in PTSD symptoms in both arms were similar in size to other active, evidence-based treatments for PTSD, such a cognitive processing therapy (Bohus et al 2020, Sloan et al 2022, Resick et al, 2017), cognitive behavioral therapy, prolonged exposure, eye-movement desensitization and reprocessing (Bradley et al, 2005).

This study marks the first RCT of a group-based PTSD treatment program derived from IFS. There has been an urgent need in public health for group-based PTSD treatment programs, in order to provide accessibility, cost-effectiveness, as well as the beneficial effects of group treatment that comes from being with others who have similar mental health conditions. The finding that the PARTS group had better group attendance and member satisfaction suggests that PARTS is a promising group-based treatment program for PTSD, and supports the need for further research.

The Collaborative Research Team

The article about this latest study is co-authored by a team led by Principal Investigator Zev Schuman-Olivier, MD, Director of CMC, and includes contributions from lead author Diane Joss, PhD, as well as Alexandra Comeau, MA, River Chevannes, MSW, Gareth Parry, PhD, Hanna Soumerai Rea, MA, Javier Barria, MS, Clare Bumpus, BS, Ashley Rector, MD, Adhithi Rajan, PsyD, Joseph Rosansky, PhD, Fiona Kate Rice, LMHC, Mary Catherine Ward, MA, Laure Tobiasz Veltz, MS, Dilara Ally, PhD, Martha Sweezy, PhD, and David Lovas, PhD.

Understanding Internal Family Systems

Internal Family Systems (IFS) is a popular, integrative, contemplative, mental health intervention that integrates elements from various psychotherapeutic approaches. IFS has been shown to enhance decentering (a form of mindful meta-awareness), self-compassion, and emotion regulation skills (Comeau, et al 2024). While clinical research on the IFS approach is nascent and more research is needed, the modality has become widely adopted with more than 14,000 clinicians trained worldwide according to the IFS Institute. Traditional IFS therapy takes place in an individual therapy setting. To develop a standardized IFS approach for research that would be accessible in community mental health settings, the PARTS program was designed using an online group format for treating PTSD.

About the Center for Mindfulness and Compassion

The Center for Mindfulness and Compassion at Cambridge Health Alliance is dedicated to integrating evidence-based mindfulness and compassion interventions into healthcare, education, and the community. To learn more, visit the Center’s website..

About the Foundation for Self-Leadership

The study was supported by grants from the Foundation for Self-Leadership, which is a 501(c)(3) organization that exists to foster greater emotional, relational and societal healing and wellbeing—leading to a more peaceful world. The analysis and findings in this publication represent the scientific perspectives of the authors alone and do not reflect the opinions or views of the Foundation, which has had no involvement in the study or its analyses or deliberations. More info and resources are available through the Foundation's website.

The Foundation is always grateful to its hundreds of donors, including the IFS Institute, who continue to make its programs possible.

Contact

For further details about the study, the PARTS program, or to explore training opportunities, please visit the Center's website. For more information about the Foundation's research-incubation efforts, please reach out to This email address is being protected from spambots. You need JavaScript enabled to view it..

Citations

Joss D, Comeau A, Chevannes R, Parry G, Rea HS, Barria J, Bumpus C, Rector A, Rajan A, Rosansky J, Rice FK, Ward MC, Tobiasz Veltz L, Ally D, Rosenberg LG, Sweezy M, Lovas D, Schuman-Olivier Z. A randomized controlled trial of an online group-based internal family systems treatment for posttraumatic stress disorder: The Program for Alleviating and Resolving Trauma and Stress (PARTS) study. Psychol Trauma. 2026 Jan 29. doi: 10.1037/tra0002089. Epub ahead of print. PMID: 41609644.

Comeau A, Smith LJ, Smith L, Soumerai Rea H, Ward MC, Creedon TB, Sweezy M, Rosenberg LG, Schuman-Olivier Z. Online group-based internal family systems treatment for posttraumatic stress disorder: Feasibility and acceptability of the program for alleviating and resolving trauma and stress. Psychol Trauma. 2024 Dec;16(Suppl 3):S636-S640. doi: 10.1037/tra0001688. Epub 2024 Jun 27. PMID: 38934934.

Ally D, Tobiasz-Veltz L, Tu K, Comeau A, Bumpus C, Blot T, Rice FK, Orr B, Soumerai Rea H, Sweezy M, Schuman-Olivier Z. A pilot study of an online group-based Internal Family Systems intervention for comorbid posttraumatic stress disorder and substance use. Front Psychiatry. 2025 Mar 27;16:1544435. doi: 10.3389/fpsyt.2025.1544435. PMID: 40212833; PMCID: PMC11983591.

Bohus M, Kleindienst N, Hahn C, Müller-Engelmann M, Ludäscher P, Steil R, Fydrich T, Kuehner C, Resick PA, Stiglmayr C, Schmahl C, Priebe K. Dialectical Behavior Therapy for Posttraumatic Stress Disorder (DBT-PTSD) Compared With Cognitive Processing Therapy (CPT) in Complex Presentations of PTSD in Women Survivors of Childhood Abuse: A Randomized Clinical Trial. JAMA Psychiatry. 2020 Dec 1;77(12):1235-1245. doi: 10.1001/jamapsychiatry.2020.2148. PMID: 32697288; PMCID: PMC7376475.

Sloan DM, Marx BP, Acierno R, Messina M, Muzzy W, Gallagher MW, Litwack S, Sloan C. Written Exposure Therapy vs Prolonged Exposure Therapy in the Treatment of Posttraumatic Stress Disorder: A Randomized Clinical Trial. JAMA Psychiatry. 2023 Nov 1;80(11):1093-1100. doi: 10.1001/jamapsychiatry.2023.2810. PMID: 37610727; PMCID: PMC10448372.

Sloan DM, Thompson-Hollands J, Hayes AM, Lee DJ, Alpert E, Marx BP. Sudden Gains in Two Trauma-Focused Treatments for Posttraumatic Stress Disorder. Behav Ther. 2022 Mar;53(2):255-266. doi: 10.1016/j.beth.2021.08.003. Epub 2021 Aug 30. PMID: 35227402; PMCID: PMC8896295.

Resick PA, Wachen JS, Dondanville KA, Pruiksma KE, Yarvis JS, Peterson AL, Mintz J; and the STRONG STAR Consortium; Borah EV, Brundige A, Hembree EA, Litz BT, Roache JD, Young-McCaughan S. Effect of Group vs Individual Cognitive Processing Therapy in Active-Duty Military Seeking Treatment for Posttraumatic Stress Disorder: A Randomized Clinical Trial. JAMA Psychiatry. 2017 Jan 1;74(1):28-36. doi: 10.1001/jamapsychiatry.2016.2729. Erratum in: JAMA Psychiatry. 2017 Jun 1;74(6):655. doi: 10.1001/jamapsychiatry.2017.0935. PMID: 27893032.

Bradley, R., Greene, J., Russ, E., Dutra, L., Westen, D., 2005. A Multidimensional Meta-Analysis of Psychotherapy for PTSD. American Journal of Psychiatry 162, 214–227. https://doi.org/10.1176/appi.ajp.162.2.214