4 Conclusions

We identified 16 eligible systematic reviews that included 326 primary studies overall; of these, 35 primary studies evaluated 43 experimental interventions delivered directly to 17,950 students during normal school hours. Findings suggest that school-based anxiety prevention interventions may have a positive impact on anxiety among students. Our confidence in meta-analytic findings is reduced by the number of studies with plausible explanations other than differences in interventions received (i.e., risks of bias). For anxiety diagnoses, our confidence is also reduced by imprecision (i.e., a confidence interval that includes average effects of both reduced and increased risk of an anxiety diagnosis). Moreover, there is substantial unexplained heterogeneity in study effect estimates and wide prediction intervals, even in the meta-regression with significant moderator test for whether studies included public schools—and we did not detect a statistically significant moderation effect when examining the five discrete levels of school type. Consequently, while the evidence suggests schools implementing these interventions in contexts similar to those in the review are more likely than not to see improvements in anxiety diagnoses and symptoms, users of this evidence should be aware that current research evidence suggests both positive and negative effects are possible, and we do not have strong evidence to indicate what predicts positive versus negative effects. Strengths of this review include the use of explicit research questions and eligibility criteria, prospective registration of the review protocol, eligibility assessment and data collection in duplicate, use of established techniques to assess risk of bias, and use of meta-analytic techniques that include all (dependent) effect sizes reported in eligible primary studies (even when the exact form of the dependence is unknown). Potential ways to improve the strengths of this review are to supplement our literature search for systematic review (e.g., grey and non-English literature sources) and conduct our own supplemental search for primary studies.