School Mental Health Interventions for Adolescents: A Meta-Analysis of Effectiveness and Relevant Moderators

(1) Background: School-based mental health interventions represent a promising approach to address the substantial treatment gap affecting adolescents, with only 20% of youth with diagnosable mental health conditions receiving adequate care. (2) Methods: This meta-analysis synthesized evidence from 18 randomized controlled trials to examine the effectiveness of school-based mental health interventions and potential moderators of outcomes. (3) Results: Using Hedges's g as the effect size index and a random-effects model, the analysis revealed a statistically significant overall effect size of 0.068 (95% CI [0.019, 0.117], p = 0.006), indicating small but reliable improvements in adolescent academic, social, emotional, behavioral, and mental health outcomes. Heterogeneity across studies was minimal (I² = 15%), suggesting consistent effects across diverse intervention types and contexts. Meta-regression analyses examining nine potential moderators including intervention focus, grade level, provider type, delivery format, duration, study design, geographic location, and theoretical foundation did not reveal statistically significant moderation effects, likely due to limited statistical power. However, descriptive patterns suggested that targeted interventions, small-group formats, and interventions delivered by mental health professionals may produce larger effects than universal programs, classroom-based approaches, and teacher-delivered interventions. (4) Conclusions: These findings support continued investment in school-based mental health programming while highlighting the need for specialized focus to optimize outcomes for all adolescents.