Fraguas D, Díaz-Caneja CM, Ayora M, et al. - Across 77 samples from 69 randomized clinical trials (111,659 participants [56,511 in the intervention group and 55,148 in the control group]), researchers sought to evaluate the efficacy of school anti-bullying interventions, their population impact, and the correlation between moderator variables and outcomes. During follow-up, the efficacy of anti-bullying programs did not diminish over time. The population impact of school anti-bullying interventions seemed to be substantial despite the small effect sizes and some regional variations in effectiveness. Better planned trials that determine the optimum timing and length of intervention are warranted.