Community Mental Health Service User-Led Discharge Planning and Readmission Risk in South African Districts: A Stepped-Wedge Cluster Evaluation

User-led discharge planning is widely promoted as a means of reducing readmission after psychiatric inpatient care, yet the district-level evaluations that would justify its expansion in South Africa rest on designs whose operating characteristics have not been characterised. Power was estimated across 2000 design cells for cluster counts of 8, 16, 24 and 32 and effect sizes of 3, 5 and 8 percentage points.54 clusters are required to detect a 5 percentage point reduction in readmission at 80 per cent power under this variance structure, a requirement that exceeds the cluster counts typically available to South African district mental health services. Minimum detectable effects at 80 per cent power fall steeply as cluster counts rise, and the density of estimated power across replications is wide at small cluster counts. The contribution is a design-characterisation result: it specifies the cluster counts at which a stepped-wedge evaluation of user-led discharge planning can and cannot credibly detect plausible effects, and it identifies the variance components that dominate the power calculation. The implication is that district evaluations should be planned around the minimum detectable effect rather than the nominal effect size, and that pooled or regional designs are required where district cluster counts fall below the threshold identified here.