Olweus, D. (2005). A useful evaluation design, and effects of the Olweus Bullying Prevention Program. Psychology, Crime & Law, 11(4), 389–402. https://doi.org/10.1080/10683160500255471

Type of Study: Pretest–posttest study with a nonequivalent control group (Quasi-experimental)
Number of Participants: Approximately 21,000

Population:

• Age — Not specified
• Race/Ethnicity — Not specified
• Gender — Not specified
• Status — Participants were students.

Location/Institution: Norway

Summary: (To include basic study design, measures, results, and notable limitations)
The purpose of the study was to examine the effectiveness of the Olweus Bullying Prevention Program (OBPP). Participants were grouped into cohorts that received treatment over the course of three years. Measures utilized include the Bully/Victim Questionnaire. Results indicate that there were quite substantial reductions in bully/victim problems. The ‘‘time-series’’ nature of the data showed convincingly that a ‘‘history interpretation’’ of the findings is very unlikely. Limitations include reliance on self-reported measures; missing data; may not be generalizable to other schools wishing to implement the program, given the inherent complexity required for program implementation; and historical factors in the study setting.

Length of controlled postintervention follow-up: 8 months.

Bauer, N. S., Lozano, P., & Rivara, F. P. (2007). The effectiveness of the Olweus Bullying Prevention Program in public middle schools: A controlled trial. Journal of Adolescent Health, 40(3), 266–274. https://doi.org/10.1016/j.jadohealth.2006.10.005

Type of Study: Pretest–posttest study with a nonequivalent control group (Quasi-experimental)
Number of Participants: 6,518

Population:

• Age — Approximately 10–14 years (grades 6–8)
• Race/Ethnicity — 32% White, 25% Asian, 20% Black or African American, 10% Other, 7% Hispanic or Latino, and 2% Native American
• Gender — 51% Female
• Status — Participants were students in grades 6–8.

Location/Institution: 10 public middle schools in Seattle

Summary: (To include basic study design, measures, results, and notable limitations)
The purpose of the study was to examine the effectiveness of the Olweus Bullying Prevention Program. Participants were grouped into treatment consisting of the Olweus Bullying Prevention Program. Measures utilized include the Revised Olweus Bully/Victim Questionnaire. Results indicate that the Olweus Bullying Prevention Program showed no overall effect on student victimization. However, when stratified by ethnicity/race, reports of relational and physical victimization decreased by 28% and 37% respectively, among white students relative to those in comparison schools. No similar effect was found for students of other races/ethnicities; there were no differences by gender or by grade. Students in intervention schools were more likely to perceive other students as actively intervening in bullying incidents, and 6th graders were more likely to feel sorry and want to help victims. Limitations include reliance on self-reported measures; missing data; may not be generalizable to other schools wishing to implement the program, given the inherent complexity required for program implementation; and historical factors in the study setting.

Length of controlled postintervention follow-up: 2 years.

Farrell, A. D., Sullivan, T. N., Sutherland, K. S., Corona, R., & Masho, S. (2018). Evaluation of the Olweus Bully Prevention Program in an urban school system in the USA. Prevention Science, 19(6), 833–847. https://doi.org/10.1007/s11121-018-0923-4

Type of Study: Other quasi-experimental
Number of Participants: 1,791

Population:

• Age — Fall Wave 6th Graders: Mean=11.3 years; Fall Wave 7th Graders: Mean=12.3 years; Fall Wave 8th Graders: Mean=13.4 years
• Race/Ethnicity — 81% Black or African American, 15% Hispanic or Latino, 5% White, and 1% Other. Note: Participants were able to identify themselves in multiple racial categories.
• Gender — 53% Female
• Status — Participants were urban middle school students.

Location/Institution: Public Middle schools in the United States

Summary: (To include basic study design, measures, results, and notable limitations)
The purpose of the study was to evaluate the effectiveness of the Olweus Bully Prevention Program (OBPP) in urban middle schools that served a predominantly African American student population. Participants were randomized into waves of treatment in a multiple baseline study design over the course of 5 years. Additional students were recruited each year to replace those promoted to 9th grade or who left the school for other reasons. Measures utilized include OBPP study developed surveys measuring student and teacher ratings/reports on bullying, aggression, victimization, and school safety. Results indicate that there were significant reductions in teachers’ ratings of students’ frequency of engaging in verbal, relational, and physical aggression, and on verbal and relational, but not physical victimization following implementation of the OBPP during the different years of implementation. These effects were consistent across schools and gender, but varied across grades for relational and verbal aggression and for victimization. In contrast to teachers’ ratings, there were no intervention effects on students’ reports of their behavior. Effects on verbal and relational aggression first appeared in the second year of implementation, but effects on physical aggression were not evident until the third year. These findings were consistent across schools and gender, and were sustained across subsequent years of intervention. Variations in when effects emerged across outcomes suggest that changes in physical aggression require more sustained effort. This may be particularly true in urban schools where adolescents may feel compelled to respond aggressively to forms of provocation they feel cross the line. Positive outcomes for teacher, but not student reports, suggest that the intervention’s effects may have been limited to the school context. Limitations include delayed implementation of the intervention in the schools, differences in the school rates of problems, bias in teacher and student ratings, and challenges in implementing OBPP in under resourced school settings.

Length of controlled postintervention follow-up: None.

Limber, S. P., Olweus, D., Wang, W., Masiello, M., & Breivik, K. (2018). Evaluation of the Olweus Bullying Prevention Program: A large scale study of U.S. students in grades 3–11. Journal of School Psychology, 69, 56–72. https://doi.org/10.1177/02711214020220020101

Type of Study: Pretest–posttest study with a nonequivalent control group (Quasi-experimental)
Number of Participants: Study 1 (n=70,998); Study 2 (n=31,675)

Population:

• Age — Approximately 7–18 years (grades 3–11)
• Race/Ethnicity — Study 1: 62% White, 17% Missing Data, 12% Other, 5% Black/ African American, and 5% Hispanic/Latino; Study 2: 61% White, 20% Missing Data, 11% Other, 5% Black/African American, and 3% Hispanic/Latino
• Gender — Study 1: 51% Male, 49% Female, and 0.4% Missing Data; Study 2: 50% Male, 49% Female, and 0.4% Missing Data
• Status — Participants were children and youth in grades 3–11.

Location/Institution: 49 counties in southern and central Pennsylvania

Summary: (To include basic study design, measures, results, and notable limitations)
The purpose of the study was to evaluate a large-scale implementation of the Olweus Bullying Prevention Program with children and youth in grades 3–11 in the U.S. Two major sets of analyses are presented, one following 210 schools over two years (Study 1; n=70,998 at baseline) and the other following a subsample of 95 schools over three years (Study 2; n=31,675 at baseline). Participants were grouped into treatment consisting of the Olweus Bullying Prevention Program. Measures utilized include the Olweus Bullying Questionnaire (OBQ). Results indicate that for almost all grades there were clear reductions in the two key dimensions: being bullied and bullying other students. Average absolute change amounted to approximately 3%, implying that almost 2000 students had escaped being bullied in the two-year study. School-level Cohen's d's were large or fairly large. The longitudinal analyses documented increases in students' expressions of empathy with bullied peers, marked decreases in their willingness to join in bullying, and perceptions that their primary teacher had increased their efforts to address bullying. Overall, effects were stronger the longer the program had been in place. Limitations include study did not employ an experimental design using random assignment of schools to intervention or control conditions, inability to rule out possible effects of other school-based programs that may have been implemented within intervention schools during the evaluation period, and findings can be primarily generalized to schools in Pennsylvania with a demographic predominance of White students from schools in primarily suburban and rural locales.

Length of controlled postintervention follow-up: 2 and 3 years.

Olweus, D., Limber, S. P., & Breivik, K. (2019). Addressing specific forms of bullying: A large-scale evaluation of the Olweus Bullying Prevention Program. International Journal of Bullying Prevention, 1(1), 70–84. https://doi.org/10.1207/s19309325nhsa0601_6

Type of Study: Pretest–posttest study with a nonequivalent control group (Quasi-experimental)
Number of Participants: 31,620

Population:

• Age — Approximately 7–18 years (grades 3–11)
• Race/Ethnicity — 61% White, 20% Missing data, 11% Other, 5% Black/African American, and 3% Hispanic/Latino
• Gender — 50% Male, 49% Female, and 0.4% Missing Data
• Status — Participants were students in Grades 3–11.

Location/Institution: 49 counties in Southern and Central Pennsylvania

Summary: (To include basic study design, measures, results, and notable limitations)
The study used a subset of the same sample as Limber et al. (2018).The purpose of the study was to evaluate the effectiveness of the Olweus Bullying Prevention Program (OBPP) in reducing specific forms of bullying—verbal bullying, physical bullying, and indirect/relational bullying, as well as cyberbullying and bullying using words or gestures with a sexual meaning. Participants were grouped into treatment consisting of the Olweus Bullying Prevention Program. Measures utilized include the Olweus Bullying Questionnaire (OBQ). Results indicate that OBPP was successful in reducing all forms of being bullied and bullying others. Analyses by grade groupings (grades 3–5, 6–8, and 9–11) revealed that, with only a few exceptions, there were significant program effects for all forms of bullying for all grade groupings. For most analyses, program effects were stronger the longer the program was in place. Most analyses indicated similar and substantial effects for both boys and girls, but a number of program by gender interactions were observed. Program effects for Black and White students were similar for most forms of being bullied and bullying others. Although Hispanic students showed results that paralleled the development for Black and White students for particular grade groups and variables, they were overall somewhat weaker. Limitations include nonrandomization of participants, reliance on self-reported measures, and lack of generalizability due to ethnicity of participants.

Length of controlled postintervention follow-up: 1–3 years.

Olweus, D., Solberg, M. E., & Breivik, K. (2020). Long-term school-level effects of the Olweus Bullying Prevention Program (OBPP). Scandinavian Journal of Psychology, 61(1), 108–116. https://doi.org/10.1111/sjop.12486

Type of Study: Pretest–posttest study with a nonequivalent control group (Quasi-experimental)
Number of Participants: 172 elementary schools

Population:

• Age — Approximately 5–13 years (grades 1–7)
• Race/Ethnicity — Not specified
• Gender — Not specified
• Status — Participants were elementary schools for grades 1–7 with continued and repeated use of the Olweus Bullying Questionnaire (OBQ)..

Location/Institution: Norway

Summary: (To include basic study design, measures, results, and notable limitations)
The purpose of the study was to assess the efficacy of the Olweus Bullying Prevention Program (OBPP). Participants were grouped into treatment consisting of the Olweus Bullying Prevention Program. Measures utilized include the Olweus Bullying Questionnaire (OBQ) and the National Pupil Survey. Results indicate that A-schools (elementary schools) with continued use had changed their “school culture” for the better with regard to awareness, preparedness, and competence in handling and preventing bullying. Limitations include nonrandomization of intervention group, reliance on self-reported measures, and lack of follow-up.

Length of controlled postintervention follow-up: None.

Sullivan, T. N., Farrell, A. D., Sutherland, K. S., Behrhorst, K. L., Garthe, R. C., & Greene, A. (2021). Evaluation of the Olweus Bullying Prevention Program in US urban middle schools using a multiple baseline experimental design. Prevention Science, 22(8), 1134–1146. https://doi.org/10.1007/s11121-021-01244-5

Type of Study: Other quasi-experimental
Number of Participants: 2,755

Population:

• Age — 6th Graders: Mean=11.5 years; 7th Graders: Mean=12.7 years; 8th Graders: Mean=13.7 years
• Race/Ethnicity — 78% Black/African American, 17% Hispanic/Latino, 6% White, 1% Asian, Native Hawaiian or Pacific Islander, Asian, Native Alaskan, or American Indian. Note: Participants were able to identify themselves in multiple racial categories
• Gender — 52% Female
• Status — Participants were urban middle school students.

Location/Institution: Public middle schools in the United States

Summary: (To include basic study design, measures, results, and notable limitations)
The purpose of the study was to evaluate the effectiveness of the Olweus Bully Prevention Program (OBPP) in urban middle schools that served a predominantly African American student population. Participants were randomized into waves of treatment in a multiple baseline study design over the course of 5 years. Additional students were recruited each year to replace those promoted to 9th grade or who left the school for other reasons. Measures utilized include OBPP study developed surveys measuring student and teacher ratings/reports on bullying, aggression, victimization, and school safety. Results indicate that for teacher ratings of student behavior, we found significant main effects across all subtypes of aggression and victimization, with some variability in the timing of effects. The pattern of findings showed delayed intervention effects for boys and a weaker impact of the OBPP on 6th graders. Main effects for student-reported cyber aggression and victimization, relational aggression, and a composite of physical, verbal, and relational victimization were found. Decreases in victimization emerged in the 1st or 2nd year of intervention, and reductions in aggression emerged during the 3rd year. Across all findings, once intervention effects emerged they remained significant in subsequent intervention years. The OBPP resulted in significant decreases in student- and teacher-reported aggression and victimization. However, this intervention had limited impact on general areas of school climate including teacher support, positive peer interactions, and school safety. Limitations include small effect sizes, lack of procedural fidelity data for on-the-spot-interventions, and concerns for merger of students from two different attendance zones.

Length of controlled postintervention follow-up: None.