Mechanistic targets of Internal Family Systems in the treatment of posttraumatic stress disorder

High rates of childhood trauma and PTSD commonly characterize individuals seeking care at community outpatient clinics. Growing evidence suggests compassion-based therapies counteract the emotion dysregulation and self-judgment that maintain PTSD severity. Internal Family Systems (IFS) therapy is grounded in compassion, mindfulness, and contemplative inner dialogue. Though primarily an individual therapy for over 40 years, a group adaptation called PARTS (Program for Alleviating and Reducing Trauma and Stress) has recently demonstrated feasibility, acceptability, and preliminary efficacy when implemented as an online 16-week clinical service in an urban community clinic. This study aimed to identify novel mechanistic targets of IFS among 30 patients with PTSD enrolled in the PARTS program. The sample was 70% female, with 47% meeting criteria for Complex PTSD. Comorbid conditions were common, including depressive disorders, substance use, suicidal ideation, and bipolar disorder. Participants completed eight self-report assessments at baseline and post-program. Exploratory factor analysis and Bayesian hierarchical regression were used to estimate intervention effects and change associations. Two factors explained 60% of variance in clinical measures: (1) Compassionate Awareness (CA), comprising decentering and self-compassion; and (2) Self-critical Rumination Dysregulation Cascade (SRDC) consisting of self-critical rumination and emotion dysregulation. The intervention was associated with increased CA, reduced SRDC, and reduced PTSD symptoms. CA change was negatively associated with PTSD change independent of SRDC, which showed a positive association. Higher baseline PTSD scores were associated with attenuated CA gains. These findings highlight compassion as a key treatment target in community trauma care, particularly where self-critical rumination and dysregulation are key symptom features.