RCT Testing Bystander Effectiveness to Reduce Violence

Abstract

Introduction: Bystander-based programs have shown promise to reduce interpersonal violence at colleges, yet limited rigorous evaluations have addressed bystander intervention effectiveness in high schools. This study evaluated the Green Dot bystander intervention to reduce sexual violence and related forms of interpersonal violence in 26 high schools over 5 years.

Design: A cluster RCT was conducted.

Setting/participants: Kentucky high schools were randomized to intervention or control (wait list) conditions.

Intervention: Green Dot-trained educators conducted schoolwide presentations and recruited student popular opinion leaders to receive bystander training in intervention schools beginning in Year 1.

Main outcome measures: The primary outcome was sexual violence perpetration, and related forms of interpersonal violence victimization and perpetration were also measured using anonymous student surveys collected at baseline and annually from 2010 to 2014. Because the school was the unit of analysis, violence measures were aggregated by school and year and school-level counts were provided.

Results: A total of 89,707 students completed surveys. The primary, as randomized, analyses conducted in 2014-2016 included linear mixed models and generalized estimating equations to examine the condition-time interaction on violence outcomes. Slopes of school-level totals of sexual violence perpetration (condition-time, p<0.001) and victimization (condition-time, p<0.001) were different over time. During Years 3-4, when Green Dot was fully implemented, the mean number of sexual violent events prevented by the intervention was 120 in Intervention Year 3 and 88 in Year 4. For Year 3, prevalence rate ratios for sexual violence perpetration in the intervention relative to control schools were 0.83 (95% CI=0.70, 0.99) in Year 3 and 0.79 (95% CI=0.67, 0.94) in Year 4. Similar patterns were observed for sexual violence victimization, sexual harassment, stalking, and dating violence perpetration and victimization.

Conclusions: Implementation of Green Dot in Kentucky high schools significantly decreased not only sexual violence perpetration but also other forms of interpersonal violence perpetration and victimization.

Figure 1

CONSORT diagram for study enrollment, allocation, and data collection and analysis. ^aNumber present is the number of students in school on the day of the survey administration by year and condition. Each year all students in the schools were surveyed, thus student numbers differ by year. Individual students are not followed over time. The number of students enrolled defined as those administratively enrolled at each school at the beginning of the academic year across all schools by condition was used as the denominator for response rate calculation reported in text. ^bRefusals include both student and parental refusal of study participation. ^cMissing includes students agreeing to participant yet completing no demographic items nor violence or intervention training items. ^dStudent responses were identified as potentially “mischievous” if there were discrepancies between similar questions (e.g., never drinker reporting binge drinking). ^eTwo schools initially agreed to participate in the trial and dropped out before randomization. Values for the missing school were imputed from prior year. One intervention school dropped out in Year 4 and one control school dropped in Year 1; the school-level means from the last year of data collection were used as the imputed value. No., number.