The Crisis of Adolescent Depression and the Promise of Prevention
Depression remains one of the most significant public health challenges of the 21st century, frequently emerging during the critical developmental window of early adolescence. Given that early-onset depression is a strong predictor of recurrent episodes, academic underachievement, and long-term psychosocial impairment, the medical and educational communities have increasingly turned toward universal prevention strategies. Among these, school-based mindfulness training (SBMT) has gained substantial traction globally. The logic is compelling: by teaching mindfulness—a state of nonjudgmental awareness—to all students regardless of baseline risk, schools might build psychological resilience across the entire population.
However, as the implementation of mindfulness programs has scaled, the empirical evidence supporting their effectiveness in unselected student populations has remained mixed. The My Resilience in Adolescence (MYRIAD) trial was designed to provide a definitive answer to the question of whether universal SBMT is truly superior to standard social-emotional learning. This article interprets the core findings of the MYRIAD trial, including a recent secondary analysis that utilized sophisticated machine learning to determine if specific subgroups of adolescents might still benefit from these interventions.
Study Design: The Scale of the MYRIAD Trial
The MYRIAD project was a landmark parallel-group, cluster-randomized controlled trial conducted across the United Kingdom. Between October 2016 and July 2018, the study recruited 85 secondary schools, involving over 8,000 students aged 11 to 14 years and nearly 700 teachers. This large-scale, population-representative approach was designed to minimize bias and maximize the generalizability of the findings.
Schools were randomized in a 1:1 ratio to either Teaching as Usual (TAU)—which consisted of standard social and emotional learning curricula—or the SBMT intervention. The SBMT curriculum consisted of 10 structured lessons incorporating psychoeducation and mindfulness practices. The primary endpoints were focused on participant-level risk for depression, social-emotional-behavioral functioning, and overall well-being at a one-year follow-up.
Primary Outcomes: A Neutral Verdict for Universal Mindfulness
In the primary analysis published in Evidence-Based Mental Health, the results were striking for their lack of differentiation between the two groups. Analysis of 84 schools and 8,376 participants revealed no evidence that SBMT was superior to TAU at the one-year mark. The standardized mean differences (SMD) for depression risk (0.005), social-emotional-behavioral functioning (0.02), and well-being (0.02) were all statistically non-significant and near zero.
These findings suggest that when delivered as a universal program in typical secondary school settings, SBMT does not provide the prophylactic benefit against depression that many proponents had hoped for. While the intervention was found to be safe—with no reported adverse events—the lack of superiority over standard care raised critical questions about the ‘one-size-fits-all’ approach to mental health prevention.
Machine Learning and the Quest for Personalization
A secondary analysis, led by Webb and colleagues and published in JAMA Psychiatry, sought to move beyond average treatment effects. Using data-driven algorithms, the researchers aimed to identify which individual adolescents might be most likely to benefit from SBMT based on their baseline characteristics. This approach acknowledges that while the average effect may be neutral, there could be a subset of ‘responders’ hidden within the data.
Causal Forest vs. Elastic Net: Identifying the Benefit Subgroup
The research team utilized school-level nested cross-validation to train machine learning models, specifically Causal Forest (CF) and Elastic Net Regression (ENR). These models were designed to calculate a Personalized Advantage Index (PAI), quantifying the expected benefit for an individual student if they received SBMT versus TAU.
The CF model demonstrated acceptable calibration and identified that certain features were predictive of a better response. Specifically, students with low-to-moderate baseline symptoms of depression and anxiety appeared to derive more benefit from SBMT than those with very high or very low symptoms. Additionally, several school-level factors showed nonlinear patterns in predicting outcomes, suggesting that the environment in which mindfulness is taught plays a significant role in its reception.
The Gap Between Statistical Significance and Clinical Utility
Despite the sophisticated modeling, the clinical impact of these findings was modest. While both the CF and ENR models identified a subset of adolescents predicted to benefit more from SBMT, the actual group differences in outcomes were described by the authors as ‘negligible’ or ‘clinically trivial.’ The effect sizes for the predicted benefit groups were small (d = 0.07 for CF; d = 0.08 for ENR).
This result highlights a significant challenge in precision psychiatry: identifying a statistically significant predictor of treatment response does not always translate into a clinically meaningful intervention strategy. The findings suggest that even when we attempt to personalize universal SBMT, the added value over standard care remains minimal for the vast majority of students.
The School Ecosystem: Impact on Teachers and Climate
While the student-level outcomes for depression were disappointing, the MYRIAD trial did uncover some positive signals regarding the broader school ecosystem. Analysis of teacher outcomes showed that SBMT, compared to TAU, led to short-term improvements in teacher mental health and school climate. Teachers in the SBMT group reported reduced exhaustion and a greater sense of personal accomplishment shortly after delivering the program.
Furthermore, improvements were noted in ‘respectful climate’ and school leadership perceptions. However, these benefits for teachers were largely transient; the effects on burnout were not maintained at the one-year follow-up. This suggests that while mindfulness training may provide a temporary boost to staff well-being and school culture, sustained impact requires more than a single 10-week intervention.
Economic Considerations and Cost-Effectiveness
An interesting facet of the MYRIAD trial was its economic evaluation. Despite the lack of clinical superiority in symptom reduction, SBMT demonstrated a high probability (83%) of cost-effectiveness at a willingness-to-pay threshold of £20,000 per quality-adjusted life year (QALY). This paradox often occurs in public health research when an intervention is relatively inexpensive to deliver at scale. Even very small, non-significant gains across a large population can sometimes reach the threshold for cost-effectiveness, though this does not necessarily justify the intervention if it displaces more effective programs.
Expert Commentary: Why Universal SBMT Underperformed
The failure of universal SBMT to show superiority over TAU in the MYRIAD trial has sparked intense discussion among child psychologists and public health experts. Several factors may explain these results:
1. Dosage and Engagement: Adolescents may require more than 10 lessons to internalize mindfulness skills. Furthermore, student engagement in universal programs can be low compared to individuals who seek out mindfulness training voluntarily.
2. The Strength of the Comparator: The TAU group received social and emotional learning, which is already a relatively high standard of care in UK schools. Mindfulness may not offer enough incremental benefit over these existing programs.
3. Developmental Timing: Early adolescence is a period of significant neurological and social flux. It is possible that the cognitive demands of mindfulness—such as meta-awareness—are difficult for all 11-to-13-year-olds to master simultaneously in a classroom setting.
4. Universal vs. Targeted Approaches: The results reinforce the ‘prevention paradox.’ While universal programs reach everyone, they may lack the intensity needed to help those at highest risk, while those at low risk have little room for improvement.
Conclusion: Moving Beyond Universalism in School Mental Health
The MYRIAD trial represents a milestone in adolescent mental health research, providing a rigorous, data-driven critique of universal school-based mindfulness. The findings clearly state that SBMT is not a ‘silver bullet’ for the adolescent depression crisis. While it is safe and may offer short-term benefits for teacher well-being, its impact on student mental health outcomes is comparable to standard social-emotional teaching.
Furthermore, the secondary machine learning analysis suggests that even with advanced personalization, we cannot yet reliably identify a subgroup of students for whom universal SBMT offers a major clinical advantage. Future research should perhaps pivot away from universal classroom delivery and toward more intensive, targeted interventions for high-risk youth, or explore how to integrate mindfulness more deeply and sustainably into the school culture rather than as a brief, standalone curriculum.
Funding and Trial Registration
The MYRIAD trial was funded by the Wellcome Trust (WT104908/Z/14/Z, WT107496/Z/15/Z). The trial is registered at isrctn.org (Identifier: ISRCTN86619085).
References
1. Webb CA, Ren B, Hinze V, et al. Predicting Adolescent Response to School-Based Mindfulness: A Secondary Analysis of the MYRIAD Trial. JAMA Psychiatry. 2026; doi: 10.1001/jamapsychiatry.2025.4638.
2. Kuyken W, Ball S, Crane C, et al. Effectiveness and cost-effectiveness of universal school-based mindfulness training compared with normal school provision in reducing risk of mental health problems and promoting well-being in adolescence: the MYRIAD cluster randomised controlled trial. Evid Based Ment Health. 2022;25(3):99–109.
3. Kuyken W, Ball S, Crane C, et al. Effectiveness of universal school-based mindfulness training compared with normal school provision on teacher mental health and school climate: results of the MYRIAD cluster randomised controlled trial. Evid Based Ment Health. 2022;25(3):125–34.
