Effectiveness and Cost-Effectiveness of a Digital Mindfulness-Based Intervention for Psychological Distress Delivered by Trainee Instructors: A Randomized Controlled Trial

INTRODUCTION: The high prevalence of psychological distress and shortage of mental health professionals create a service gap for highly symptomatic populations exceeding routine care capacity. We evaluated a hybrid digital mindfulness intervention (MIED) delivered via a train-the-trainer (TTT) model for reducing psychological distress and providing economic value. METHODS: In this randomized controlled trial in China, adults with significant psychological distress (Kessler-10 score ≥22) were assigned (1:1) to 8-week MIED plus services as usual (SAU), or SAU alone. The primary outcome was the 8-week trajectory of psychological distress. Secondary outcomes included mental health indicators and short-term cost-utility. Intention-to-treat analyses used generalized estimating equations (GEEs). RESULTS: Between November 1 and 8, 2024, 1,281 participants were assigned (MIED: n = 641; SAU: n = 640). GEE revealed a significant Group × Time interaction for distress (χ2 (4) = 143.611, p < 0.001), with the intervention group demonstrating greater reductions than SAU (Cohen's d = -0.526 at Week 8). Secondary indicators also improved (p < 0.001). From a societal perspective, MIED incurred lower mean costs (993 CNY [∼USD 140] vs. 1,326 CNY [∼USD 186]; p < 0.001) with 95% probability of cost-effectiveness at 9,246 CNY [∼USD 1,299] per quality-adjusted life-year. Adherence was high (mean, 6.04 of 8 sessions). No severe adverse events were identified, and self-reported meditation-related adverse experiences declined over time within the intervention group. CONCLUSIONS: Compared with SAU, TTT-delivered MIED is a safe, effective, and potentially cost-saving adjunct strategy for scaling MIED delivery in resource-constrained systems. Future research should evaluate long-term sustainability beyond 8 weeks.