RESUMEN
Background: There is a need for more sustainable interventions and for assessing the effectiveness of school-based universal anti-bullying programmes in vulnerable populations. We assessed the efficacy of a multicomponent, web-enabled, school-based intervention that aims to improve school climate and reduce bullying (LINKlusive) relative to conventional practices (control condition). Methods: We conducted a cluster randomised controlled trial in primary and secondary schools in Madrid, Spain. The primary outcome measure was peer-reported bullying victimisation after the 12-week intervention (study endpoint). We analysed data using longitudinal mixed-effects models. The trial was registered with the ISRCTN registry (15719015). Findings: We included 20 schools (10 in each group); 6542 students participated at baseline; 6403 were assessed at study endpoint. After the intervention, there was a statistically significant reduction in bullying victimisation in both the intervention (OR 0.61, 95% CI [0.41, 0.90]) and control groups (OR 0.69, 95% CI [0.51, 0.92]), with no evidence of differences in the whole sample (OR 0.89, 95% CI [0.58, 1.36]; aOR 0.89, 95% CI [0.58, 1.37]). Subgroup analyses showed a statistically significant effect of LINKlusive on bullying victimisation in primary education (aOR 0.68, 95% CI [0.47, 0.98]). In students with peer-reported bullying victimisation at baseline, LINKlusive showed a statistically significant effect on depression (-1.43, 95% CI [-2.46, -0.40], adjusted standardised mean difference (SMD) -0.41) and quality of life (2.18, 95% CI [0.80, 3.56], adjusted SMD 0.45). Interpretation: LINKlusive could be effective in reducing bullying victimisation in primary school students. Sustainable whole-school interventions to promote mental health and reduce risk factors are warranted to improve outcomes in young people, especially in the early years of education. Funding: Instituto de Salud Carlos III, Spanish Ministry of Science and Innovation.
