Evaluation of the effectiveness of SOM-RIU, a multifaceted, school-based, suicide prevention intervention targeted to Spanish adolescents: study protocol for a cluster-randomised controlled trial

Adolescent suicide is a major public health concern and the third leading cause of death among young people worldwide. Schools are widely recognized as effective settings for universal mental health promotion and suicide prevention. This study aims to evaluate the effectiveness of SOM-RIU, a multifaceted school-based intervention involving pupils and gatekeepers (teachers and parents) in preventing suicidal behaviour and promoting adolescent mental health. We will conduct a six-month, two-arm, cluster-randomised controlled trial. We will recruit 2,280 pupils from 114 classrooms in 38 secondary schools across the Balearic Islands (Spain). Eligible pupils will be aged 12–16 and enrolled in the 2nd and 3rd years of compulsory secondary education. Schools will be randomly assigned (1:1) to either the intervention or control group. Schools in the intervention group will implement the SOM-RIU programme, which includes four weekly psychoeducational sessions for pupils, delivered by trained educational psychologists. These sessions focus on mental health literacy, emotional regulation, suicide risk detection and management, and help-seeking strategies. In parallel, gatekeepers (teachers and parents) will receive a digital educational co-intervention consisting in four multimedia modules to strengthen their role in suicide prevention. Schools in the control group will receive a minimal intervention consisting of educational posters on mental health and suicide prevention displayed within school premises. The primary outcome will be suicidal ideation (Paykel Suicide Scale). Secondary outcomes will include suicide attempts, depression symptoms, well-being, self-harm, substance use, internet addiction, bullying, and cognitive disconnection. Teachers and parents will report on suicide-related knowledge, self-efficacy, and student referrals. Data will be collected at baseline and six-month follow-up. Analyses will be conducted using generalized linear mixed models to account for clustering, and multiple imputation will be used for missing data. A qualitative process evaluation will explore implementation, acceptability, and perceived impact of the intervention, while also examining contextual factors and potential mechanisms of action that may have influenced the outcomes. This trial will generate evidence on the effectiveness of multifaceted, school-based suicide prevention interventions for adolescents. If effective, the SOM-RIU programme could serve as a practical model for enhancing mental health support within educational settings in Spain. NCT06996054 (clinicaltrials.gov). Registration date: 2025-05-30.