Hannah Gaffney|Maria M. Ttofi|David P. Farrington
Effectiveness of school?based programs to reduce bullying perpetration and victimization: An updated systematic review and meta?analysis
University of Cambridge|University of Cambridge|University of Cambridge
bullying first emerged important topic research 1980s norway olweus recent metaanalysis shows forms aggression remain prevalent among young people globally modecki et al prominent researchers field defined bullying aggressive behavior incorporates three key elements namely 1 intention harm 2 repetitive nature 3 clear power imbalance perpetrator victim centers disease control prevention farrington many negative outcomes associated bullying perpetration suicidal ideation holt et al weapon carrying valdebenito et al drug use ttofi et al violence offending later life ttofi et al bullying victimization associated negative outcomes suicidal ideation holt et al anxiety low selfesteem loneliness hawker boulton therefore school bullying important target effective intervention considered matter public health concernthe objective review establish whether existing schoolbased antibullying programs effective reducing schoolbullyng behaviors report also updates previous metaanalysis conducted farrington ttofi earlier review found antibullying programs effective reducing bullying perpetration victimization primary objective current report update earlier analysis 53 evaluations conducting new searches evaluations conducted published since 2009systematic searches conducted using boolean combinations following keywords bully victim bullyvictim school intervention prevention program evaluation effect antibullying searches conducted several online databases including web science pscyhinfo embase embase dare eric google scholar scopus databases unpublished reports masters doctoral theses eg proquest also searchedresults systematic searches screened thoroughly following inclusion criteria included review study must 1 described evaluation schoolbased antibullying program implemented schoolage participants 2 utilized operational definition schoolbullying coincides existing definitions 3 measured schoolbullying perpetration andor victimization using quantitative measures self peer teacherreport questionnaires 4 used experimental quasiexperimental design one group receiving intervention another receiving interventionof 19877 search results 474 retained screening majority excluded multiple waves screening 100 evaluations included metaanalysis total 103 independent effect sizes estimated effect size corrected impact including clusters evaluation designs included evaluations conducted using randomized n 45 ie randomized controlled trialsrcts nonrandomized n 44 ie quasiexperimental designs beforeafter measures baec methodologies studies included measures bullying outcomes implementation intervention remaining 14 effect sizes estimated evaluations used age cohort designs two models metaanalysis used report results report mean effects computed presented using multivariance adjustment model mva random effects model mva model assigns weights primary studies direct proportion study level sampling error fixed effects model adjusts metaanalytic standard error confidence intervals study heterogeneity model incorporates betweenstudy heterogeneity formula assigning weights primary studies differences strengthslimitations approaches discussed context present dataour metaanalysis identified bullying programs significantly reduce bullying perpetration odds ratio 1309 95 confidence interval ci 124138 z 988 p 001 bullying victimization 1244 95 ci 119131 z 892 p 001 random effects model metaanalysis mean effects similar across models metaanalysis bullying perpetration ie mva 1324 95 ci 127138 z 134 p 001 bullying victimization ie mva 1248 95 ci 121129 z 1206 p 001 computational models primary studies effective reducing bullying perpetration victimization overall effect sizes varied across studies significant heterogeneity studies bullying perpetration q 323392 df 85 p 001 i2 73716 bullying victimization q 387255 df 87 p 001 i2 77534 outcomes analyses suggest publication bias unlikely betweenstudy heterogeneity expected given large number studies included thus number different programs methods measures samples usedwe conclude overall schoolbased antibullying programs effective reducing bullying perpetration bullying victimization although effect sizes modest impact evaluation methodology effect size appears weak adequately explain significant heterogeneity primary studies moreover issue underoverestimation true treatment effect different experimental designs use selfreported measures reviewed potential explanations discussed along recommendations future primary evaluations avenues future research discussed including need explain differences across programs correlating individual effect sizes varying program components varying methodological elements available across 100 evaluations initial findings variability effect sizes across different methodological moderators provide understanding issue heterogeneity future analyses based moderator variables needed