Background:
Victimization among children is associated with adverse effects on their physical and psychological health. Many health complaints follow as a result of bullying and anxiety and depression also precede bullying. The Dutch school-wide antibullying program ‘Prima’ was developed based on techniques and scientific insights that are known to be effective. In this randomized trial we investigate the effects of school-wide antibullying program on bullying behavior and self-esteem and depression.

Methods:
A total of 4,229 students of grade 3 to 6 of 31 primary schools
participated in this study. The schools were randomly assigned to three conditions. Condition A was offered a teachertraining, an online screening tool for bullying behavior, and a set of practice- and evidence-based guidelines to deal with difficult bullying situations. Condition B included all of condition A plus a series of eight lessons for the students. Condition C was the control group. A questionnaire was filled out by the students before and after the intervention.

Results:
Results from the pretest showed that 16% of the students was bullied regularly. There was a significant difference between bullied and non-bullied children in their reported mental health. Bullied students indicated much more depressive symptoms compared to non-bullied students (3,67 vs 1,67, p= .000). Bullied children also indicated lower self-esteem (16,74 vs 19,84, p = .000). The effects of the intervention program are currently analyzed and will be presented at the conference in the fall of 2018.

Conclusions:
Bullying is strongly related to mental health issues among children. To address mental health issues among youth, schools should focus on evidence-based anti-bullying programs as a vital part of a wider school policy.
Key messages:
-Bullying has a strong impact on the wellbeing and mental health of children.
-School programs focused on preventing bullying can therefore reduce health complaints among children.