Effectiveness of a school-based universal prevention program on self-efficacy and mental health problems in Japanese children: differences between universal- and indicated-level effects

Mental health problems among children and adolescents have been increasing worldwide, highlighting the need for preventive interventions in schools. This study examined the effectiveness of a school-based universal prevention program on self-efficacy and mental health problems in Japanese children using a quasi-experimental design with intervention and control groups. A total of 1,281 third- and fourth-grade students participated, with 264 assigned to the intervention group and 1,017 to the control group. The intervention group received the Universal Unified Prevention Program for Diverse Disorders (Up2-D2), a 12-session program based on cognitive-behavioral and positive psychological interventions. A significant universal-level effect was found for positive attitude (a self-efficacy subscale), which improved over time in the intervention group but not in the control group. At the indicated level, a Time × Group interaction was observed for depressive symptoms among children with elevated baseline depression; however, the group effect at Time 4 did not reach statistical significance after covariate adjustment. Effect sizes at Time 4 were small for positive attitude at the universal level (g = 0.19) and small-to-moderate for depressive symptoms at the indicated level (g = 0.36). These findings suggest that Up2-D2 may promote positive attitude at the universal level, while potential indicated-level benefits for depressive symptoms may warrant further confirmation. Evaluating outcomes in both general and at-risk subgroups may help clarify for whom and on which outcomes universal school-based prevention programs are most beneficial.