Fidelity of Mindfulness Training and Delivery for Adolescent Mental and Metabolic Health.

OBJECTIVES: Adolescent-onset type 2 diabetes (T2D) is increasing, and depression symptoms amplify T2D risk, highlighting the need for interventions addressing mental and metabolic health. This multisite pilot RCT assessed whether facilitators could be trained consistently to deliver group MBI, cognitive behavioral therapy (CBT), and a matched health education condition (HE) to adolescents at risk for T2D with elevated depression symptoms. It was hypothesized that facilitators would achieve ≥ 80% on knowledge, competence, and adherence following standardized training. METHOD: Facilitators at four U.S. sites received training in MBI, CBT, and/or HE through didactics and supervised virtual mock sessions. Training fidelity was assessed through pre/post-training knowledge tests and expert ratings of adherence/competence in mock sessions. Intervention delivery fidelity was assessed with expert ratings of virtual pilot group sessions with adolescents. Contamination across conditions was evaluated. RESULTS: Seventeen facilitators were trained in MBI (n = 11), CBT (n = 10), and/or HE (n = 9). Descriptive feasibility metrics are presented; between-arm comparisons are not made. Knowledge scores improved across conditions (MBI: 76% → 96%, p = 0.01; CBT: 68% → 92%, p = 0.01; HE: 84% → 96%, p = 0.02). Median competence/adherence met or exceeded the 80% threshold for mock (MBI = 80%/85%, CBT = 86%/90%, HE = 82.5%/80%) and pilot (MBI = 90%/100%, CBT = 90%/90%, HE = 97.5%/96%) sessions. Contamination was limited to overlapping MBI-CBT content. CONCLUSIONS: Results support the feasibility of high-fidelity training and implementation of MBI, CBT, and HE across diverse settings, informing future research into integrated adolescent health prevention strategies. PREREGISTRATION: ClinicalTrials.gov #NCT04992299. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at https://doi.org/10.1007/s12671-026-02975-8.