What Works for Whom in Anti-Bullying Interventions? An Individual Participant Data Meta-Analysis

• In Event: Health promotion interventions involving children and adolescents: what works, for whom, and under which circumstances ?

Abstract

The prevalence of bullying worldwide is high: one out of three children is bullied–once or repeatedly–every month (UNESCO, 2018). Over the past decades, many anti-bullying interventions were developed to remediate this problem. However, we lack insight into ‘what works for whom’: which components drive intervention effects, and for whom do such components work (or not)? We conducted a first-ever, large-scale individual participant data (IPD) meta-analysis, using data from 39,793 children and adolescents aged five to 20 years (Mage = 12.58 , SD = 2.34) who had participated in quasi-experimental or randomized controlled trials of anti-bullying interventions (i.e., 10 studies, testing 9 interventions). Results from multi-level logistic regression analyses showed that anti-bullying interventions lead to significant reductions in self-reported victimization (Standardized effect size d = -0.14) and bullying perpetration (Standardized effect size d = -0.07). Anti-bullying interventions more strongly reduced bullying perpetration in younger participants (i.e., under age 12). None of the specific components were related to stronger anti-bullying intervention effects for the whole group. Our results further provided strong evidence that intervention components work better for some than others: many components (e.g., student placement, psycho-education, peer involvement, and school conferences) had differential effects dependent on youths’ gender and initial level of victimization and bullying perpetration. These results provide a basis for tailoring anti-bullying interventions to specific (sub)populations in primary, middle, and secondary schools.

Keywords: individual participant data (IPD) meta-analysis; anti-bullying interventions; effectiveness; bullying; victimization

Group Authors

BIRC: the anti-Bullying Interventions Research Consortium

Authors

• Maud Hensums, University of Amsterdam
  Presenting Author

• Brechtje De Mooij, University of Amsterdam
  Non-Presenting Author

• Steven Kuijper, Amsterdam UMC
  Non-Presenting Author

• Minne Fekkes, Netherlands Organisation for Applied Scientific Research
  Non-Presenting Author

• Geertjan Overbeek, University of Amsterdam
  Non-Presenting Author