Transdiagnostic Sleep Intervention to Improve Mental Health in Adolescents

This cluster randomized controlled trial will evaluate whether a brief, school-based group adaptation of the Transdiagnostic Intervention for Sleep and Circadian Dysfunction (TranS-C) improves sleep and mental health in adolescents aged 14 to 17 years. Public secondary schools in Navarre (Spain) will be randomly assigned, stratified by urban/rural location, to deliver either TranS-C or an attention-matched healthy-habits psychoeducation program. Both programs consist of four weekly 45-minute group sessions delivered during school hours by trained psychologists. The main questions it aims to answer are: Does TranS-C improve sleep quality and daytime sleepiness compared with the control program? Does TranS-C reduce anxiety-depressive symptoms, psychotic-like symptoms, interpersonal difficulties and substance use compared with the control program? Participants will complete self-report questionnaires at baseline, after the intervention, and 3, 6 and 9 months after the intervention.

Inclusion Criteria: * Aged 14 to 17 years * Enrolled in compulsory secondary education (ESO), upper secondary (Bachillerato) or vocational training (FP) in a participating public school in Navarre, Spain * Written informed consent from the participant and their legal guardian(s) * Valid self-report responses (≥75% correct answers) Exclusion Criteria: * Comprehension difficulties that prevent participation (e.g., language disorders) * Severe physical or mental health problems that prevent participation in the program * Currently receiving pharmacological or psychological treatment for sleep problems