Community-Based Trauma Mental Health Lay Counsellor Supervision Frequency and Post-Traumatic Stress Disorder Symptom Relapse Among Congolese Survivors: A Target-Trial Emulation of Supervision Interval Thresholds

Supervision intervals for lay counsellors delivering trauma-focused mental health care in conflict-affected settings are typically set by organisational convention rather than by evidence linking supervision frequency to client outcomes. No observational data were analysed; the study evaluated the design's power to detect effects of 3, 5 and 8 percentage points across 8, 16, 24 and 32 clusters, with 2000 replications per design cell, under a between-cluster standard deviation of 6.0, a residual standard deviation of 4.5 and an intraclass correlation of 0.640. Power curves, minimum detectable effect estimates and coefficient plots were generated to map the design's sensitivity. The analysis indicates that 56 clusters are required to detect a 5 percentage point difference at 80% power, and that the intraclass correlation of 0.640 substantially constrains the information available from each additional cluster. Target-trial emulation offers a defensible framework for evaluating supervision policies when randomisation is infeasible, and it specifies the design parameters under which such an evaluation would yield interpretable estimates of supervision interval effects on relapse.