Post Cluster-Randomized Controlled Trial: Longer-Term Efficacy of a Bystander Program to Reduce Violence Perpetration and Victimization in a Prospective Cohort

Purpose: In this cohort analyses, we sought to estimate the longer-term efficacy of a high-school based bystander intervention to reduce gender-based violence (GBV) into young adulthood. Methods: Seniors were recruited from 23 of 26 high schools that participated in the original RCT (2010–2014) designed to test the effectiveness of a bystander intervention to reduce GBV. Of 3,389 high school seniors who completed an electronic survey in their last term, 1,986 complete at least one annual follow up survey through 2018 (58.6% retention). Receipt of bystander training was defined based on (1) the high school the participant attended (‘as randomized’ in the original RCT) and (2) participants’ report of additional bystander training received after high school (‘as reported’). The primary GBV outcomes were sexual violence perpetration and victimization rates (%) for the past 12 months. Results: Only at the final follow up were significant reductions in sexual violence perpetration (SVP) noted for the ‘as randomized’ analyses. Self-reported SVP rates were 38% lower (adjusted rate ratio = 0.62; 95% Confidence Interval (CI): 0.48–0.81) among 1,107 participants who had attended schools randomized to the bystander intervention (SVP = 2.1%: 95% CI; 1.6–2.9) relative to 877 participants who had attended control schools (SVP = 3.4%; 95% CI: 3.0-3.9). Receipt of additional bystander training after high school was not associated with lower rates of any GBV form when compared with participants receiving no bystander training in or after high school. Conclusions: Bystander training was not consistently associated with longer-term reductions in GBV perpetration nor victimization in this prospective cohort study based on a large school-based RCT.