Participant and Intervention Characteristics that Moderate Treatment Outcomes among Adolescents with Anxiety and Anxiety-Related Symptoms among Adolescents Aged 12–18 Years

Anxiety and anxiety-related symptoms are major mental health concerns during adolescence that impair psychosocial and academic functioning. This systematic review and meta-analysis synthesised therapeutic interventions for anxiety in adolescents aged 12–18 years and investigated moderators. We conducted the review following PRISMA 2020 guidelines, and searches across major databases identified eligible studies published from January 2004 to December 2024. Effects were expressed as Hedges’ g and pooled using random-effects models, with risk of bias and certainty assessed via RoB 2 and GRADE. Fourteen independent studies from 10 countries were included (12 psychological, 1 pharmacological and 1 combined). The overall pooled effect was statistically significant (Hedges’ g = 0.417, 95% CI [0.203, 0.632], p < .001), with substantial heterogeneity (I² = 74.41%) and a prediction interval of −0.352 to 1.186. Valid between-category comparisons across intervention types were precluded because the pharmacological and combined categories each contained only one study. Delivery format showed a significant omnibus association among psychosocial categories, Q between (2) = 8.94, p = .011, without establishing pairwise superiority. Trim-and-fill analysis adjusted the pooled effect to g = 0.295. The overall certainty of the evidence was rated as moderate. The findings indicate a positive average intervention effect with considerable variability. Because the prediction interval crossed zero, effects in future comparable settings may vary, highlighting the need to interpret outcomes as an average association rather than uniform effectiveness and underscoring the need for further research on pharmacological and combined approaches.