Health Action in ScHools for a Thriving Adolescent Generation (HASHTAG): a feasibility trial of a school-based intervention for mental health promotion and prevention among adolescents in South Africa.

Schools play a crucial role in supporting adolescent mental health, especially in low- and middle-income countries (LMICs), where young people face structural and societal challenges. This study explores the feasibility and acceptability of the Health Action in Schools for a Thriving Adolescent Generation (HASHTAG), a multilevel intervention for at-risk adolescents aged 13-14 in South Africa. HASHTAG includes two components: thriving environment in schools (TES), a whole-school approach, and thriving together (TT), a classroom-based programme. Using a mixed-methods design, we assessed feasibility in two Khayelitsha schools through implementation measures (attendance, fidelity and acceptability), focus groups (n = 46), and pre-post surveys (n = 231). Despite COVID-19 disruptions, the intervention was implemented with high fidelity and met all progression criteria. Students and staff found HASHTAG relevant and engaging, particularly appreciating the TT sessions delivered by external facilitators. The TES teacher module also created space for reflection and self-care. Some teachers suggested improved sensitisation could strengthen the programme's impact. Although no significant changes were observed in quantitative outcomes, no harms were reported. These findings support the feasibility and acceptability of HASHTAG and highlight the need for a full-scale trial to evaluate its potential impact on adolescent mental health in LMIC settings.