1. Bibliographic Information

1.1. Title

Reducing LGBTQ+ adolescent mental health inequalities: a realist review of school-based interventions

1.2. Authors

Elizabeth McDermott, Alex Kaley, Eileen Kaner, Mark Limmer, Ruth McGovern, Felix McNulty, Rosie Nelson, Emma Geijer-Simpson & Liam Spencer.

The authors are affiliated with several UK-based institutions, including Lancaster University and the University of Bristol. Their collective expertise appears to span public health, sociology, mental health, and youth studies, making them well-suited for this interdisciplinary research topic.

1.3. Journal/Conference

The paper was published in the Journal of Mental Health. This is a reputable, peer-reviewed international journal that focuses on all aspects of mental health for researchers and practitioners. Its publication in this journal indicates that the research meets rigorous academic standards and is relevant to the field of mental health.

1.4. Publication Year

2024 (Accepted: 27 June 2023)

1.5. Abstract

The abstract outlines the core problem: Lesbian, Gay, Bisexual, Transgender, Queer/Questioning, and other identities (LGBTQ+) young people face significantly higher rates of poor mental health compared to their cisgender heterosexual peers, with the school environment being a major contributing factor. This study uses a realist review methodology to investigate how, why, for whom, and in what contexts school-based interventions are effective in reducing mental health issues for this demographic. After synthesizing seventeen studies, the authors identified eight crucial intervention components that form a programme theory. The key finding is that few targeted interventions exist, and those that are effective must adopt a whole-school approach. This approach must specifically challenge the pervasive cis-heteronormative school environment to combat the marginalization, silence, and victimization experienced by LGBTQ+ students, thereby improving their mental health.

1.6. Original Source Link

The official publication link is: https://doi.org/10.1080/09638237.2023.2245894

The paper is officially published and available through the journal's website. The provided /files/papers/69056b5f0b2d130ab3e047fa/paper.pdf is a copy of the final published version.

2. Executive Summary

2.1. Background & Motivation

The core problem addressed by this paper is the stark mental health inequality between LGBTQ+ adolescents and their cisgender heterosexual counterparts. Existing research consistently shows that LGBTQ+ youth experience higher rates of depression, self-harm, and suicidality. A significant driver of this disparity is the school climate, which is often characterized by a culture of cis-heteronormativity—the assumption that all students are cisgender (identify with the gender they were assigned at birth) and heterosexual. This environment fosters peer victimization, bullying, and a lack of safety, all of which are linked to negative mental health outcomes.

While some interventions, like the whole-school approach to tackling homophobic, biphobic, and transphobic (HBT) bullying, have been identified, a critical gap exists in the literature. Previous reviews have focused on what interventions work but have not robustly explained how and why they work. There is a lack of theoretical understanding of the underlying mechanisms that connect a school intervention to an improvement in an LGBTQ+ student's mental health. This gap makes it difficult to transfer successful interventions to different contexts or to design new, effective ones.

The paper's innovative entry point is its use of a realist review, a methodology specifically designed to unpack the complexity of social interventions. Instead of just asking "Does this intervention work?", it asks, "What works, for whom, under what circumstances, how, and why?". This approach aims to build a comprehensive theoretical model to explain the causal pathways from intervention to outcome.

2.2. Main Contributions / Findings

The paper's primary contribution is the development of a programme theory that explains how school-based interventions can effectively reduce mental health inequalities for LGBTQ+ adolescents. This theory provides a detailed map of the causal links between intervention components, the changes they trigger, and the ultimate impact on mental health.

The key findings are:

1. Identification of Eight Essential Intervention Components: An effective, whole-school approach requires a combination of the following components:

   • Affirmative visual displays (e.g., posters)
   • External signposting to LGBTQ+ support services
   • Stand-alone input (e.g., special assemblies)
   • School-based LGBTQ+ support groups (e.g., Gay-Straight Alliances)
   • Curriculum-based delivery (integrating LGBTQ+ topics into lessons)
   • Staff training
   • Inclusion policies
   • The presence of a trusted adult

2. A Multi-faceted Causal Mechanism: The programme theory proposes that these interventions work by triggering changes across multiple levels (vectors of change): the school environment, interpersonal relationships, individual behaviors, self-perceptions, and emotions. These changes, in turn, activate positive cognitive responses (cognition) in students, such as feelings of affirmation, agency, belonging, connectedness, safety, and recognition.

3. The Necessity of a Whole-School Approach: The review concludes that isolated or single-component interventions are insufficient. To be effective, interventions must systemically challenge the dominant cis-heteronormative culture of the school, addressing structural, cultural, and individual-level factors simultaneously.

3. Prerequisite Knowledge & Related Work

3.1. Foundational Concepts

3.1.1. Realist Review (or Realist Synthesis)

A realist review is a theory-driven approach to evidence synthesis, differing significantly from a traditional systematic review.

• Traditional Systematic Review: Asks "What works?" It aims to determine the overall effectiveness of an intervention by aggregating results from high-quality studies (often randomized controlled trials). The goal is to produce a generalizable, bottom-line summary of an intervention's effect.
• Realist Review: Asks "What works, for whom, in what circumstances, how, and why?" It acknowledges that interventions are not "magic bullets" but complex social programs whose success depends heavily on context. It seeks to uncover the underlying mechanisms (the "how" and "why") that explain how an intervention ($I$) produces certain outcomes ($O$) in specific contexts ($C$). The central output is not a judgment of effectiveness, but a refined programme theory expressed as Context-Mechanism-Outcome (CMO) configurations.

3.1.2. Programme Theory

In the context of a realist review, a programme theory is a set of explicit hypotheses or models that explain how an intervention is expected to work. It outlines the entire causal chain: the intervention's resources, how participants are expected to respond to them, and the intended outcomes. This paper starts with an Initial Theory and refines it through the review process to produce a final, evidence-based Programme Theory.

3.1.3. Context-Mechanism-Outcome (CMO) Configuration

This is the core analytical unit of a realist review.

• Context (C): The conditions or circumstances in which the intervention is implemented. This includes factors like pre-existing school culture, national policies, or the presence of a staff "champion."
• Mechanism (M): The underlying processes that are triggered by the intervention and generate the outcomes. It's not the intervention itself, but the response to the intervention. For example, an inclusive curriculum (intervention) might trigger a mechanism of "recognition" in a student. The authors of this paper further break down mechanisms into intervention resources, vectors of change, and cognition.
• Outcome (O): The results of the intervention, both intended and unintended. In this paper, outcomes are changes in mental health status (e.g., reduced suicidality, increased self-esteem).

3.1.4. Cis-heteronormativity

This term describes the pervasive social and cultural assumption that all individuals are cisgender (their gender identity aligns with the sex they were assigned at birth) and heterosexual. In a school context, this manifests as curricula that only depict heterosexual relationships, gender-segregated activities (e.g., boys' and girls' sports teams), and a general silence or invisibility around LGBTQ+ identities. This paper argues that cis-heteronormativity is the root problem that interventions must address.

3.1.5. Whole-School Approach

A whole-school approach is an intervention strategy that aims to change the entire school environment rather than focusing on isolated activities or individuals (like punishing a single bully). It involves multiple components that target different levels of the school system, including school policies, curriculum content, staff training, student support, and the physical environment. The goal is to create a comprehensively inclusive culture.

3.2. Previous Works

• Mitchell et al. (2014, 2016): These authors conducted a large-scale evaluation of a UK government-funded program to tackle homophobic, biphobic, and transphobic (HBT) bullying in over 900 schools. Their research was foundational for this review because it identified seven key elements of a whole-school approach. However, a crucial limitation noted by the current paper is that this evaluation did not measure the impact on student mental health, focusing only on bullying. This paper builds on Mitchell et al.'s work by linking the whole-school components directly to mental health outcomes.

• Black et al. (2012): This was a systematic review on the impact of "safe school" interventions on LGBTQ+ youth. It grouped effective interventions into three themes: inclusive programs (like Gay-Straight Alliances), supportive policies, and a supportive environment. The current paper notes that while this review identified key components, it was based on sparse evidence (mainly from the US and Canada) and only approximated the explanations for why these interventions work, rather than robustly investigating the mechanisms.

• Meyer (2003) - Minority Stress Model: This is a highly influential psychological theory explaining health disparities in minority populations. Though only cited, its principles are central to the paper's logic. The model posits that LGBTQ+ individuals experience unique stressors related to their stigmatized identity (e.g., discrimination, prejudice, internalized homophobia). These chronic stressors accumulate and lead to adverse mental health outcomes. The interventions discussed in the paper can be understood as efforts to mitigate these minority stressors within the school context.

• Formby (2015): This work argues that a narrow focus on HBT bullying is insufficient. It critiques approaches that only target individual bullies and calls for a multi-level approach that challenges the broader cis-heteronormative culture of schools. This aligns with the current paper's conclusion that a whole-school approach is necessary.

3.3. Technological Evolution

The field has evolved from a narrow focus on individual-level problems to a broader, systemic understanding.

1. Early Stage (Individual Focus): Initial efforts concentrated on HBT bullying as an interpersonal problem between a "bully" and a "victim." Interventions were often punitive and reactive, aimed at punishing individual perpetrators.
2. Intermediate Stage (Programmatic Focus): The focus shifted to specific programs, such as Gay-Straight Alliances (GSAs), and their direct impact on students who participated. Research began to show that the presence of a GSA was correlated with better outcomes for all students, not just members.
3. Current Stage (Systemic/Ecological Focus): The understanding has broadened to the concept of school climate. Researchers now recognize that bullying and exclusion are symptoms of a deeper systemic issue: cis-heteronormativity. The most advanced approach, and the one advocated by this paper, is the whole-school approach, which treats the entire school environment as the target of the intervention. This paper's use of a realist review represents a methodological evolution, moving beyond measuring if an intervention works to explaining how it works within this complex system.

3.4. Differentiation Analysis

The core innovation of this paper lies in its methodology.

• Previous Reviews (e.g., Black et al., 2012): These were typically traditional systematic reviews. They aggregated findings to determine what interventions (e.g., GSAs, anti-bullying policies) are associated with better outcomes. They provided a "list" of effective components but offered limited, often speculative, explanations of the causal processes.
• This Paper (Realist Review): This paper does not just list components; it builds a theory to explain the connections between them. Its primary goal is to articulate the CMO configurations. The key differentiation is the focus on mechanisms. For example, instead of just saying "GSAs are effective," it theorizes that GSAs work by providing a space that triggers mechanisms of belonging, affirmation, and agency, which in turn reduce feelings of isolation and improve self-esteem, leading to better mental health outcomes. The introduction of the "vector of change" concept is a further methodological refinement, providing a more granular explanation of where and how change occurs.

4. Methodology

4.1. Principles

The study is grounded in the realist review methodology, a theory-driven approach developed for analyzing complex social interventions where context is crucial and randomized controlled trials (RCTs) are often inappropriate. The core principle is that interventions don't "work" on their own; they provide resources that people choose to engage with, and it is this engagement within a specific context that produces outcomes. The goal is to move beyond simple "what works" questions to a more nuanced understanding of "what works, for whom, under what circumstances, how, and why?" by developing and refining a programme theory.

4.2. Core Methodology In-depth (Layer by Layer)

The authors followed the established seven-step realist review protocol.

4.2.1. Step 1: Scoping the Literature

The first step was a preliminary search to determine if there was sufficient literature to conduct a realist review. This initial scoping confirmed that while evidence was sparse, certain features were consistently associated with a positive school climate for LGBTQ+ youth. These included:

• Anti-discrimination policies

• Gay-Straight Alliances (GSAs)

• LGBTQ+-inclusive curriculum

• Supportive teachers and peers

  This confirmed the feasibility of the review.

4.2.2. Step 2: Developing the Initial Theory

This is a critical step in a realist review. The authors constructed an Initial Theory to guide their main search and synthesis. This theory was not created in a vacuum but was built from four key sources:

1. Middle Range Theories (MRTs): Six existing theories from psychology, sociology, and queer theory were used to provide high-level explanations for mental health disparities in LGBTQ+ populations. These included theories from Meyer (minority stress), Hatzenbuehler (stigma), and others.

2. UK National Reports (Mitchell et al., 2014, 2016): The findings from the national evaluation of the anti-HBT bullying program provided a practical framework, identifying seven core components of a whole-school intervention.

3. Youth Advisory Group (YAG): In a crucial step for ensuring stakeholder engagement, the researchers recruited five young LGBTQ+ people (ages 15-22) as paid members of the research team. Through focus groups and vignettes, the YAG helped shape and validate the initial theoretical ideas from their lived experiences.

4. Empirical Papers: Findings from the initial scoping review were also incorporated.

   This process resulted in the Initial Theory, which is visualized in Figure 1 of the paper. This diagram posits that the seven intervention components from the UK reports lead to changes in the school environment, which in turn improve mental health outcomes.

The following figure (Figure 1 from the original paper) shows the Initial Theory:

该图像是论文中展示的示意图，说明学校干预措施如何通过不同路径减少LGBTQ+青少年的精神健康问题，包括肯定性视觉展示、外部支持标识、独立活动、支持小组、课程教学、员工培训和包容政策等多种干预措施及其效果。

4.2.3. Step 3: Search Strategy

With the Initial Theory as a guide, the authors conducted a comprehensive and iterative search for relevant evidence.

• Databases: They searched discipline-specific databases (PubMed, PsycINFO, Embase, ERIC, CINAHL) and multidisciplinary ones (Web of Science, Google Scholar, Scopus).

• Keywords: Search terms covered five domains: (i) sexual orientation and gender identity, (ii) age, (iii) education, (iv) mental health and wellbeing, and (v) intervention.

• Timeframe: The search covered literature from January 1999 to March 2021. The start date of 1999 was chosen to reflect the modern era of greater legal and social liberalization regarding LGBTQ+ rights in the West, ensuring the relevance of the findings to contemporary school settings.

• Other Strategies: They also searched grey literature (reports from organizations like Stonewall), conducted forward citation tracking, and consulted with subject experts. The search was considered complete when theoretical saturation was reached, meaning new evidence was no longer adding significant new insights to the developing programme theory.

  The following figure (Figure 2 from the original paper) shows the PRISMA diagram of the search process:

  该图像是一个PRISMA流程图，展示了通过数据库检索筛选文献的过程，明确了包括的研究数量及排除标准，反映出文献筛选的详细步骤。

4.2.4. Step 4: Inclusion and Exclusion Criteria

Studies were selected based on relevance to the research questions. The criteria were applied by four researchers to ensure consistency.

The following are the criteria from Table 1 of the original paper:

4.2.5. Step 5: Quality Appraisal

In realist reviews, quality appraisal rejects the traditional "hierarchy of evidence" (where RCTs are at the top). Instead, studies are appraised based on two criteria:

1. Relevance: Does the study contribute to building or refining the programme theory? Can it shed light on a CMO configuration?
2. Rigour: Is the study's methodology trustworthy enough to make a credible contribution? The authors used a four-question checklist to assess rigour, asking if the paper described its research setting, empirical methods, mental health outcomes, and the intervention itself.

4.2.6. Step 6: Data Extraction

A data extraction template was designed to capture information relevant to realist synthesis. For each of the 17 included studies, the authors extracted:

• Study details (author, year, location)

• Intervention type

• Context (C)

• Mechanism (M)

• Outcome (O)

  This extraction was done "in conversation" with the Initial Theory, meaning the data was actively used to test, challenge, and refine the initial hypotheses.

4.2.7. Step 7: Data Synthesis

This is the final and most crucial step, where the extracted data is used to produce the final Programme Theory. The authors used several analytical techniques:

• CMO Configuration Tabulation: They tabulated the CMO configurations for each included paper.

• Integration with MRTs: They used the six initial Middle Range Theories to deepen the theoretical explanations of the causal pathways. For example, Meyer's minority stress model helped explain why an inclusive environment (Context) with a GSA (Mechanism 1) could lead to reduced suicidality (Outcome).

• Youth Advisory Group Workshop: They held a workshop with the YAG to get their input on the developing theory, further enhancing its real-world validity.

• Refinement of the Mechanism Concept: A key methodological innovation was the disaggregation of the Mechanism concept. Building on Dalkin et al. (2015), they split it into intervention resources and response mechanism (which they call cognition). They then added a novel third element, the vector of change, to specify what changes as a result of the intervention (e.g., the school culture, relationships, individual thoughts).

  This synthesis process allowed them to move from the Initial Theory to the more detailed and evidence-based final Programme Theory presented in the results.

5. Experimental Setup

As this is a realist review, the "experimental setup" refers to the body of literature that was synthesized.

5.1. Datasets

The "dataset" for this review consists of the 17 empirical studies that met the inclusion criteria. The characteristics of this corpus of literature are:

• Source and Scale: The studies were predominantly from North America (12 from the USA, 4 from Canada) with only one from Europe (Netherlands). No studies from the UK were included. Many studies were based on large-scale survey data, with some sample sizes in the tens of thousands.

• Characteristics and Domain: Most studies were quantitative surveys ($n=12$), with few qualitative ($n=2$) or mixed-methods ($n=1$) designs. The most frequently studied interventions were Gay-Straight Alliances (GSAs, $n=7$) and school policies ($n=2$).

• Data Example: The studies analyzed data from LGBTQ+ adolescents aged 12-20. A typical data point would be a survey response from a student identifying as bisexual, answering questions from a validated scale on depressive symptoms, and also reporting whether their school had a GSA or an enumerated anti-bullying policy.

• Reason for Selection: These 17 studies were the only ones identified through the rigorous search and screening process that evaluated a school-based intervention, measured mental health outcomes, and focused on LGBTQ+ youth within the specified age range and time frame.

  The following is the list of included studies from Table 2 of the original paper:

  Included empirical literature (n = 17)
  Bopp et al., 2004 (53)
  Burk et al., 2018 (54)
  Craig et al., 2014 (55)
  Goodenow et al., 2006 (56)
  Gunderson et al., 2021 (57)
  Hatzenbuehler & Keyes, 2013 (58)
  Hatzenbuehler et al., 2014 (59)
  Heck, 2013 (60)
  Heck, 2015 (61)
  Lapointe & Crooks, 2018 (62)
  Lindquist, 2016 (63)
  Poteat et al., 2015 (64)
  Poteat et al., 2016 (65)
  Poteat et al., 2021 (66)
  Saewyc et al., 2014 (67)
  Sandfort et al., 2010 (68)
  Zhang et al., 2018 (69)

5.2. Evaluation Metrics

The "evaluation metrics" are the mental health outcomes that were measured within the 17 included studies. The paper did not use these metrics for a meta-analysis but extracted findings related to them to build the programme theory. The key outcomes reported were:

• Suicidality: (Most frequent, $n=8$ studies) Included measures of suicidal ideation and attempts.

• Depression and Anxiety: Measured using standardized psychological scales.

• Self-Esteem: A measure of an individual's overall sense of self-worth.

• Coping: The ability to manage and overcome stressful situations.

• Other positive mental health indicators: wellbeing, purpose in life, mastery, and sense of agency.

  These outcomes are typically measured using validated self-report questionnaires (e.g., the Beck Depression Inventory, Rosenberg Self-Esteem Scale). As a review paper, the authors did not provide the specific formulas for these scales, as they were used in the primary studies being reviewed.

5.3. Baselines

In the context of this realist review, there are no "baseline models" in the computational sense. The baseline is the existing state of knowledge and the Initial Theory (Figure 1). The entire review process is designed to test and refine this initial theory against the evidence from the 17 included studies. The final Programme Theory (Table 3) represents the improved model, which stands in contrast to the simpler, less-developed initial theory.

6. Results & Analysis

6.1. Core Results Analysis

The primary result of the review is the refined Programme Theory, which explains the complex causal pathway from school-based interventions to improved mental health for LGBTQ+ adolescents. This theory is presented in Table 3 and is significantly more detailed than the Initial Theory.

The analysis reveals several key findings:

1. Limited Contextual Data: The included studies provided very little information about the Context in which interventions were successful. The authors could only identify three key contextual factors:

   • A positive pre-existing school culture towards gender and sexual diversity.
   • The presence of a "champion" (a staff member or student) driving the initiatives.
   • Supportive national or regional legal and policy directives on LGBTQ+ equality.

2. An Expanded Set of Interventions: The final theory includes eight essential Intervention Resources (Mechanism 1). This builds on the initial seven components by adding a new one identified from the literature: "Talking to a trusted adult." The evidence suggests a combination of these components, as part of a whole-school approach, is most effective.

3. A Detailed Causal Pathway: The most significant result is the detailed articulation of the mechanisms. The authors' novel three-part mechanism provides a rich explanation of how change happens:

   • Mechanism 1 (Intervention Resources): The eight components of the whole-school approach.
   • Mechanism 2 (Vector of Change): These interventions trigger change across five domains: the overall school culture, relationships between people, individual behaviors and actions, an LGBTQ+ student's self-perception and beliefs, and their affect or emotions.
   • Mechanism 3 (Cognition/Response): These changes activate crucial cognitive and emotional responses in students. These are the psychological "active ingredients." They include:
     • Affirmation: Feeling good about one's identity.
     • Agency: Feeling capable of taking action.
     • Advocacy: Feeling empowered to create change.
     • Belonging: Feeling included and not isolated.
     • Connectedness: Feeling similar to peers and staff.
     • Coping: Developing positive strategies to deal with stress.
     • Recognition: Feeling seen and valued by the school community.
     • Safety: Feeling free from fear.
     • Usualising: Feeling that being LGBTQ+ is normal and accepted.

4. Dual Outcomes: The Programme Theory shows that these interventions lead to two types of positive Outcomes: a decrease in poor mental health (e.g., lower suicidality, depression) and an increase in factors associated with good mental health (e.g., higher self-esteem, better coping skills).

6.2. Data Presentation (Tables)

The following is the final Programme Theory from Table 3 of the original paper:

6.3. Ablation Studies / Parameter Analysis

Ablation studies are not applicable to a realist review. The goal is synthesis, not testing a computational model's components. However, the analysis of the Programme Theory functions as a conceptual equivalent. By identifying eight essential Intervention Resources (Mechanism 1) and linking them to specific Vectors of Change and Cognitive responses, the review theorizes how each part contributes to the overall outcome. The strong emphasis on a whole-school approach implies that "ablating" or removing any of these eight components would likely weaken the intervention's overall effect, as they work in concert to change the systemic environment.

7. Conclusion & Reflections

7.1. Conclusion Summary

The paper successfully develops a comprehensive programme theory that explains how, why, for whom, and in what context school-based interventions can reduce mental health inequalities for LGBTQ+ adolescents. The central conclusion is that for any intervention to "work," it must adopt a whole-school approach. This approach cannot be a superficial add-on; it must be a multi-level, systemic effort to actively dismantle the dominant cis-heteronormative environment in schools. By doing so, interventions can counteract the marginalization, silence, and victimization that LGBTQ+ students face, thereby triggering mechanisms of affirmation, belonging, and safety that lead to improved mental health outcomes. The review highlights a significant gap in targeted, well-evaluated interventions and provides a vital theoretical foundation for designing and testing future ones.

7.2. Limitations & Future Work

The authors acknowledge several limitations of their review:

• Limited Source Material: The review was constrained by the limitations of the 17 included studies. Most were from North America, raising questions about transferability to other countries like the UK.

• Lack of Contextual Detail: The primary studies rarely reported on crucial contextual factors, such as the school's ethnic composition, religious affiliation, or socioeconomic status. This prevented a more granular analysis of "for whom" and "in what context" interventions work best.

• Lack of Intersectional Analysis: The included studies tended to treat "LGBTQ+" as a monolithic group, with little attention to the different experiences of lesbian, gay, bisexual, transgender, and gender diverse youth, or how identity intersects with race, disability, or class.

• Methodological Limitations of Source Data: Many studies relied on pre-existing large-scale surveys, which restricted the questions they could explore and limited the richness of the data available for realist synthesis.

• Inherent Limitations of Realist Reviews: The authors note that realist reviews are theory-oriented and do not comply with the "reproducibility principle" of traditional reviews. Their findings are therefore presented as "tentative and fallible" theoretical starting points, not certainties.

  Based on these limitations, the authors suggest future work should focus on:

• Empirically refining the programme theory to better understand contextual factors and causal pathways.

• Conducting qualitative research to explore how school cultures change.

• Developing and evaluating interventions for younger age groups.

• Improving data collection to include more detail on interventions, context, and intersectional identities.

7.3. Personal Insights & Critique

This paper is a significant contribution to the field of adolescent mental health and LGBTQ+ studies. Its main strengths are:

• Methodological Innovation: The use of a realist review is perfectly suited to this complex social problem. It moves the conversation beyond a simple checklist of "what works" to a much-needed theoretical understanding of how it works. The development of the "vector of change" concept is a thoughtful addition to the realist methodology.

• Stakeholder Engagement: The inclusion of a Youth Advisory Group as paid members of the research team is a model of excellent practice. It grounds the theoretical work in the lived experiences of the population it aims to serve, enhancing the validity and relevance of the findings.

• Actionable Framework: The final Programme Theory provides a clear, evidence-based framework for schools, policymakers, and researchers. It outlines a set of concrete components for a whole-school intervention and explains the psychological goals they should aim to achieve (e.g., fostering belonging, safety, affirmation).

  Potential issues and areas for further consideration include:

• The Challenge of Implementation: While the Programme Theory is compelling, it describes an ideal whole-school approach that would require immense resources, political will, and institutional buy-in to implement. The paper highlights that supportive national policies are a key context, but in politically polarized environments, implementing such comprehensive changes can be extremely difficult.

• Geographical Bias: The heavy reliance on North American studies is a major limitation. The social, cultural, and legal contexts for LGBTQ+ youth can vary dramatically between countries, and the Programme Theory needs to be tested and adapted for different settings, especially outside the Anglosphere.

• From Theory to Measurement: The next critical step is to develop ways to measure the mechanisms identified in the theory. How can a school quantitatively assess whether it is fostering "recognition" or "usualising" LGBTQ+ identities? Developing and validating such metrics would be essential for evaluating the success of interventions based on this theory.

  Overall, this review provides a powerful and sophisticated baseline understanding of a critical public health issue. It is a call to action for researchers and practitioners to move beyond piecemeal solutions and embrace a systemic, theory-driven approach to creating school environments where all young people can thrive.