Community-Based Trauma Mental Health Group Interpersonal Therapy Session Dosage and Post-Traumatic Stress Disorder Symptom Remission Among Congolese Refugee Women in Ugandan Settlements: A Target-Trial Emulation of Attendance Thresholds

Group interpersonal therapy (IPT-G) is a leading community-based treatment for post-traumatic stress disorder (PTSD) among conflict-affected populations in low-resource settings, yet programmes rarely specify how many sessions a woman must attend before clinically meaningful remission becomes probable. The design treats attendance as a time-varying exposure, defines sustained remission as a binary outcome measured at fixed follow-up, and specifies a BACI interaction as the estimand of interest. Using a declared variance structure (between-cluster SD = 6.0, residual SD = 4.5, intraclass correlation = 0.64) and 2000 replications per design cell, the analysis characterises power across cluster counts of 8, 16, 24, 32 and effect sizes of 3, 5, 8 percentage points. Power reached conventional levels only at the largest cluster count and effect size, and the minimum detectable effect at 80% power fell as clusters increased. The design provides a transparent template for dosage research in humanitarian mental health, and the operating characteristics indicate that settlement-level IPT-G evaluations require at least 54 clusters to detect a 5-percentage-point difference at 80% power.