Evaluation of the School-based SIM Program in Upper Secondary School Students

Söderqvist et al. recently reported on a new school-based program designed to promote mental well-being in adolescents: the Solution-Focused Intervention for Mental Health (SIM, https://doi.org/10.1016/j.ssmmh.2025.100493). While previous studies on SIM were designed mainly to test, develop, refine and improve the program and its feasibility in a school setting, the current project aims to test the efficacy of SIM on adolescent mental health, primarily mental well-being.

A two-arm, cluster, randomized, controlled trial will be conducted. The intervention group will receive the SIM program, and the control group will receive a lecture on mental well-being along with the usual school provisions. Randomization is done by class because the intervention takes place in mentor groups. Based on the results of our largest feasibility study, 559 students are required for paired measurements to detect a small effect on mental well-being with 80% power and a significance level of 0.05. The evaluation is based on validated instruments, with measurements taken before and after the intervention, as well as six and nine months later. The project is being implemented in collaboration with six upper secondary schools in Sweden. Recruitment and anchoring at the participating schools, as well as class randomization strafied on educational program, took place in 2025. Enrollment of participating students will begin in January 2026.

This project will contribute new knowledge to the field by evaluating a universal program for schools to use in their health promotion work. The latter is important since high levels of mental well-being independently predict a lower incidence of subsequent mental illness and have a range of positive effects on individuals and society.