What was done for youths aged 15 to 24 around the world? A systematic review of worldwide mental health interventions.

The global prevalence of mental health disorders among youths aged 15 to 24 is a significant public health concern. This systematic review aimed to explore global strategies for promoting mental well-being and addressing mental health challenges within this demographic, as defined by the World Health Organization. A comprehensive search of electronic scientific databases was conducted on November 1, 2023, yielding 43 studies with a total of 29,581 participants published between 2008 and 2023 that examined mental health interventions targeting youth. This review identified heterogeneity across multiple dimensions including modes and modalities of intervention delivery, conceptualisations of mental health, measurement tools and implementation settings. Digital/ technology-based interventions were prevalent in high-income countries, whereas physical interventions were more commonly employed across all income groups, especially where technological infrastructure was limited. Cognitive-behavioural therapy, psychoeducation and mindfulness-based interventions dominated the intervention modalities, likely due to their structured formats, scalability and broad applicability across a range of settings and mental health conditions. However, limited evidence of cultural adaptation in the reviewed interventions highlights the need for more inclusive and context-sensitive approaches. Schools were the most frequent delivery setting; however, reliance on educational platforms risks excluding out-of-school and marginalised youth. Conceptually, the reviewed interventions reflected both disorder-specific (diagnostic) and transdiagnostic understandings of mental health, affirming a spectrum-based view that integrates symptom reduction with well-being enhancement. This dual lens supports emerging frameworks such as the Hierarchical Taxonomy of Psychopathology (HiTOP). Measurement heterogeneity mirrored conceptual diversity, with both standardised and context-specific tools used to assess outcomes. This diversity highlighted the urgent need for culturally relevant, flexible and multi-modal interventions that span diverse settings and conceptualisations to equitably support youth mental health worldwide.