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

The Solution-Focused Intervention for Mental Health (SIM) is a universal, school-based programme designed to promote mental well-being among adolescents. Previous feasibility and development studies have supported the acceptability and feasibility of SIM in upper-secondary school settings. The present study is a two-arm, parallel-group cluster-randomised controlled superiority trial evaluating the effectiveness and cost-effectiveness of SIM among upper-secondary school students. The trial is conducted across six upper-secondary schools in Sweden. Classes are randomised in a 1:1 ratio, stratified by educational programme, to either the SIM intervention or a control condition. Students in the intervention arm receive the SIM programme in addition to usual school provision, while students in the control arm receive a lecture on mental well-being in addition to usual school provision. SIM is a structured, group-based programme applying solution-focused coaching principles and is delivered by trained school staff within ordinary school settings. The primary outcome is mental well-being, assessed using the Mental Health Continuum-Short Form. Secondary outcomes include mental health problems and perceived stress, and solution-building capability is examined as a potential mediator of intervention effects. Outcomes are assessed at baseline, immediately post-intervention, and at approximately six- and nine-month follow-up. The trial also includes process and implementation measures to assess intervention delivery and support interpretation of trial outcomes. By evaluating SIM under routine school conditions, the study aims to provide evidence on the effectiveness and cost-effectiveness of a scalable school-based approach to promoting adolescent mental well-being.