Efficacy of a prevention program for eating disorders in schools: a cluster-randomized controlled trial

BACKGROUND: Previous prevention programs in the school context have not addressed both genders, have been time-consuming, or have had deficits in the evaluation method. The aim of the present study was to evaluate the impact of a universal prevention program for female and male adolescents on eating disorder pathology and related risk factors. METHODS: Between February 2012 and July 2014, 2515 students in 23 schools from 8th or 11th grade were assessed for eligibility in this longitudinal cluster-randomized controlled trial with a six months follow-up. Of those students, 2342 were cluster-randomized to the intervention condition which received a six school hours universal prevention program or to the no treatment control condition. RESULTS: The complete case population comprised 724 students in the intervention (54.3% female, M = 14.3 years, SD = 1.61) and 728 in the control condition (57.0% female, M = 14.7 years, SD = 1.63). Random-effects analysis of covariance on the primary outcome showed no significant differences between the intervention and control groups in their eating disorder pathology change scores six months after the intervention. Regarding secondary outcomes, participants in the intervention group showed a greater increase in knowledge about eating disorders both after the intervention (p < .001, ES = 1.06) and six months later (p = .01, ES = 0.40). Greater reductions in anxiety severity were observed in the intervention group post-intervention (p = .02, ES = 0.22) which was not maintained at the six months follow-up. Results differed between participants from grade 8 and 11. CONCLUSION: The present universal prevention program can be particularly recommended for adolescents from grade 11. TRIAL REGISTRATION: ISRCTN 97989348 ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12888-017-1454-4) contains supplementary material, which is available to authorized users.