Depression, anxiety, self-harm, and suicide are prevalent mental health issues, particularly among adolescents. Rates are rising, underscoring the need for preventative public health interventions. Sexual and gender minorities (SGM) experience disproportionately high rates of these mental health problems due to minority stress – the cumulative effect of stigma, prejudice, and discrimination. Schools represent a key setting for universal interventions, which aim to address modifiable risk factors. This study addresses the lack of synthesized evidence on universal school-based interventions to promote inclusivity and acceptance of diverse sexual and gender identities, aiming to understand which interventions work, for whom, in what contexts, and why. A rapid realist review methodology was chosen to generate timely and relevant programme theories, using context-mechanism-outcome (CMO) configurations to explain how interventions interact with contexts and mechanisms to produce outcomes. The review sought to answer: 1) What universal school-based interventions exist to promote inclusivity and acceptance of diverse sexual and gender identities and how and where were they implemented? and 2) In which contexts and for whom do these interventions work (or not work) and why?

The review encompassed 53 sources (52 peer-reviewed and one non-peer-reviewed), published between 1995 and 2021, with 65% originating from North America. The sources included various designs: mixed methods, qualitative, and quantitative studies (cross-sectional, pre-post comparisons, cohort studies, and one RCT). The methodological rigor of the included studies was varied, with only 22 sources deemed fully trustworthy and credible. The review also incorporated input from a Young Person’s Advisory Group (YPAG) and a Stakeholder’s Advisory Group (SAG) to enhance the validity and relevance of the findings.

This study employed a rapid realist review methodology, adhering to RAMESES guidelines. The process involved several key steps: defining the scope and research questions; identifying the intended use of findings; developing search terms and inclusion/exclusion criteria; searching databases (PubMed, PsycINFO, Web of Science) and identifying additional sources (websites, grey literature, a call for evidence); extracting and synthesizing data; and validating findings with experts by lived experience (YPAG and SAG). The YPAG consisted of eight SGM young people (aged 14–24), who participated in meetings focused on refining the research questions, suggesting relevant sources, interpreting preliminary findings, and validating programme theories. The SAG included a school governor, a teacher, and two UK government representatives. They provided input on feasibility and relevance of findings. The study used a PRISMA flow diagram to illustrate the study selection process. Data extraction focused on study aims, design, intervention type, sample characteristics, context, mechanisms, outcomes, and CMO configurations. The initial programme theory was refined based on extracted CMOs and feedback from the reference groups. Quality assessment prioritized the rigour and relevance of sources to theory development rather than formal quality scoring. The study was pre-registered with PROSPERO.

The review identified five intervention themes: 1. **Gay-straight alliances (GSAs) and similar student clubs:** GSAs were associated with reduced bullying and improved mental health outcomes, particularly in schools with positive climates and when staff also participated. However, GSAs may not be effective in all contexts and may increase visibility leading to potential harms if the school climate is not supportive. 2. **Inclusive anti-bullying and harassment policies:** These policies were linked to increased safety and self-esteem and reduced self-harm. Effectiveness varied based on community context and policy implementation. The study highlighted the need for LGBTQ+-specific policies and effective implementation by staff. 3. **Inclusive curricula:** Curricula with positive representation of SGMs were associated with reduced bullying and improved mental health. Effective curricula should avoid deficit narratives, include LGBTQ+ role models, and be implemented early in education. 4. **Workshops including media interventions:** Workshops led by SGM individuals were associated with increased inclusivity and acceptance. The use of peer educators was found to be particularly impactful. However, potential harms were noted, including a decline in positive attitudes, particularly among male students in one study. 5. **LGBTQ+ ally and staff training:** Training significantly improved staff capacity to support SGM students, resulting in a safer school environment and better mental health outcomes. Codelivery of training by LGBTQ+ staff and students was highlighted as beneficial. Across all themes, the school climate emerged as a crucial contextual factor influencing intervention effectiveness. The study emphasized the importance of school leadership support, staff training, and the involvement of SGM students in the design and delivery of interventions. Several studies reported positive effects on self-harm and suicidality, though less data was available for depression and anxiety. Most studies were from North America or Australia, limiting generalizability to other regions.

The findings support the initial programme theory, indicating that interventions improving inclusivity and acceptance reduce the risk of mental health problems in SGM youth. The importance of school climate underscores the need for comprehensive, multi-faceted approaches. The study suggests that inclusive curricula and anti-bullying policies could precede the implementation of GSAs to create a more supportive environment. The involvement of SGM students, staff, and community experts in the design and delivery of interventions is crucial for effectiveness. The study highlights the need to adapt interventions for specific groups, including boys and bisexual students, and to address the unique challenges faced by SGM youth in different contexts.

This review identified five types of universal interventions to promote inclusivity and acceptance of diverse sexual and gender identities in schools. Programme theories were developed to explain their mechanisms of action, effectiveness, and contextual factors. School climate emerged as a critical factor, along with staff training, positive representation of SGM individuals, and involvement of SGM students and community experts. Further research, including RCTs, is needed to confirm these findings and address gaps in knowledge regarding specific SGM groups and diverse contexts.

The review’s limitations include the mixed methodological rigor of included studies, the predominantly North American/Australian sample, and limited data on specific SGM subgroups and demographic factors. The absence of a large number of RCTs also restricts the conclusions about effectiveness that can be made. The review’s reliance on self-reported data may also influence the findings.