Kailo: a systemic approach to addressing the social determinants of young people’s mental health and wellbeing at the local level

The mental health and wellbeing of children and young people is deteriorating. It is increasingly recognised that mental health is a systemic issue, with a wide range of contributing and interacting factors. However, the vast majority of attention and resources are focused on the identification and treatment of mental health disorders, with relatively scant attention on the social determinants of mental health and wellbeing and investment in preventative approaches. Furthermore, there is little attention on how the social determinants manifest or may be influenced at the local level, impeding the design of contextually nuanced preventative approaches. This paper describes a major research and design initiative called Kailo that aims to support the design and implementation of local and contextually nuanced preventative strategies to improve children's and young people’s mental health and wellbeing. The Kailo Framework involves structured engagement with a wide range of local partners and stakeholders - including young people, community partners, practitioners and local system leaders - to better understand local systemic influences and support programmes of youth-centred and evidence-informed co-design, prototyping and testing. It is hypothesised that integrating different sources of knowledge, experience, insight and evidence will result in better embedded, more sustainable and more impactful strategies that address the social determinants of young people’s mental health and wellbeing at the local level.


Need and inequalities
In general, the mental health of children and young people is deteriorating: the prevalence of many mental health disorders is on the rise; wellbeing is decreasing; and inequalities in mental health are widening for some groups (Castelpietra et al., 2022;Newlove-Delgado et al., 2022).
The picture is, of course, more nuanced than this.There are some areas of progress, such as a modest reduction in youth suicide and substance misuse rates, and the introduction of waiting time standards for accessing first episode psychosis and eating disorder services for young people (NHS England, 2021;NHS England, NICE and NCCMH, 2016;Office for National Statistics, 2022).
Yet generally speaking, the mental health and wellbeing of young people is deteriorating and the impact of this on life-course trajectories and for society remains a cause of significant concern to practitioners and policy-makers; with some describing it as being 'in crisis' (Gunnell et al., 2018).

Treatment and prevention
Over the last two decades, there has been a substantial investment in mental health services, treatment responses, and research (Cohen, 2017).This has been, in part, driven by rapid and productive advances in the life sciences which have helped inform approaches to early identification, design, and implementation of targeted and universal interventions (HM Government, 2021).
However, much of this investment is heavily skewed towards individuals, treatment responses, narrowly defined health outcomes, and mono-causal assumptions (Knapp & Wong, 2020).While significant positive advancements have been made in the treatment of mental health difficulties, current service provision for young people is almost universally described as overwhelmed, inadequately funded, and lacking capacity to meet rising demand (Lennon, 2021).
If advancement and investment in the treatment of mental health difficulties are judged to fall short, then advancements and investments in the prevention of poor mental health may be deemed wholly inadequate.
The sheer scale of need and the treatment gap (Kohn et al., 2004) means that, arguably, attempts to develop and deliver many specialised treatments require an extensive and narrow funnelling of finite resources to remedial responses (at the national and local level).This, in the language of systemic archetypes, may be considered a short-term 'fix that fails' (Hulme et al., 2022;Wolstenholme, 2003): whilst necessary, treatment only responds to surface-level manifestations of need without addressing the underlying systemic and structural drivers that perpetuate the issues.This, in turn, may further drain the finite pool of resources away from health promotive and preventive efforts, further compounding the need.Specialised treatments that rely on specialised treaters (numbers of whom cannot easily be scaled-up, especially commensurate to the extent of the existing treatment gap) paradoxically risks compounding inequality of access to help, which is in and of itself accepted as a key social determinant of mental health in a population (Compton & Shim, 2015).
So, whilst a continued and increasing investment is required in relation to the treatment of mental health disorders, this must also be accompanied by significant investment and redoubling of efforts to design, test and deliver at scale effective prevention and population-level mental health promotion approaches (Mc-Daid & Park, 2022;Muñoz et al., 1996;).).
The social determinants of young people's mental health: a systemic issue Concordant with calls for an increased emphasis on prevention, there has been growing attention to the social determinants of population health, including mental health.It is now widely acknowledged that a range of demographic, neighbourhood, social, cultural, economic, and environmental influences interact to affect young people's mental health (and exert influence upon the access to, and efficacy and impact of, services and systems of support (Compton & Shim, 2015;Lund et al., 2018).These various social determinants of mental health reciprocally drive, and are driven by, social inequities, poverty, and deeply entrenched systemic discriminations (Alegría et al., 2018).
As such, mental health may be considered a 'wicked problem' (Hannigan & Coffey, 2011) with multiple interacting synergies: it is no more attributable to a single causal agent (the rapid expansion of access to social media, for instance) than it is to, say, an inflationary redrawing of diagnostic boundaries that pathologises ordinary human distress (Lee, 2014) or the lowering of culturally-sanctioned thresholds for help-seeking (with the moral opprobrium that may accompany such observations (Thomas et al., 2018)).
Given the multitude of interacting influences, we argue that young people's mental health and wellbeing must therefore be considered a 'systems issue' (Cohen, 2017;Fried & Robinaugh, 2020;Hodges et al., 2012;Meadows, 2008).This perspective considers mental health and wellbeing as a dynamic state that varies over time and is influenced by the interactions of these wider social determinants.
It follows that efforts to improve young people's mental health require a nuanced understanding of local influences, and a multi-pronged approach to addressing locally relevant, high-impact leverage points (Betancourt et al., 2011;Groark et al., 2011;Salam et al., 2022;Ungar & Theron, 2020).

Varying manifestations at the local level
In wider fields of public health, systemic intervention efforts tend to focus on macro-system policy levers such as poverty, economic inequality, employment, housing, and transport (Marmot, 2020).There is significant potential for impact operating at this level, although sustained policy change is challenging and highly politicised.
We argue that as well as considering the macro-influences, it is also important to take a more nuanced local perspective, exploring how the social determinants of mental health are manifest at the micro/local level.The ways in which the social determinants influence young people's mental health will vary depending on local context, individual circumstance, and their local interactions (Alegría et al., 2018).To take an over-simplified example: in an inner-city urban environment, poverty may contribute to overcrowded housing, in turn, driving young people into potentially unsafe neighbourhood environments, whereas in a rural context similar levels of poverty may manifest as limited access to transport, isolation and reduced opportunities.These different risks or contexts may, in different ways, lead to the same outcome, e.g., poorer mental health (i.e., the concept of equifinality (Cicchetti & Rogosch, 1996;Fried & Robinaugh, 2020)).
Understanding and designing preventative responses in a contextually nuanced way is critical if we are to meaningfully affect underlying dynamics over time.As such, we argue that as well as considering the macro-systemic influences it is also important that we take a more nuanced local perspective, exploring how the social determinants of mental health are varyingly manifest at the micro/local level, and from this local understanding, design and implement contextually relevant preventative responses.

Existing frameworks for understanding local needs and guiding prevention efforts
There are a wide range of different approaches by which local leaders and community partnerships seek to understand local needs and context and, in turn, design and implement strategies, policies and practices to improve population mental health and wellbeing.Local needs and context may be understood, for example, via community-led and participatory action research (Burgess et al., 2022), quantitative needs assessments or school / community-based epidemiological surveys (Connors et al., 2015;Hughes et al., 2022), local stakeholder and asset mapping (Duncan et al., 2021;Public Health England, 2018) and the mapping of local system dynamics (Noubani et al., 2020;Stansfield et al., 2021).Local action or intervention may result from local co-design efforts (O'Brien et al., 2021;Tindall et al., 2021), social action and community organising (Bolton et al., 2016), through to strategic commissioning of new or existing practice, or evidence-based prevention or early intervention programmes (Boaz et al., 2019).
Over the last two decades, a number of structured 'strategic prevention frameworks' or 'operating systems' have been designed, tested and implemented (National Research Council (US) and Institute of Medicine (US) Committee on the Prevention of Mental Disorders and Substance Abuse Among Children, Youth, and Young Adults, 2009).These incorporate a series of structured steps, typically including: (i) identification of local prevention needs based on existing or new data; (ii) forming local partnerships and governance structures to identify priorities and build local capacity and momentum; (iii) identification and implementation of evidence-based programmes and practices; and (iv) ongoing monitoring, evaluation and learning.Examples include broad frameworks or guides (e.g., the US SAMHSA Strategic Prevention Framework, 2019) through to more structured approaches (such as Communities that Care (Fagan et al., 2018), PROSPER (Spoth et al., 2013) and Getting to Outcomes (Chinman et al., 2008).These prevention frameworks have, in some contexts, demonstrated positive impacts on outcomes (Brown et al., 2011;Crowley et al., 2011;Oesterle et al., 2018;Spoth et al., 2017;).
Key features and strengths of these approaches include: • Collection and synthesis of robust local data to help make the case for local action and identify priorities (Arthur et al., 2002;Axford & Hobbs, 2010).
• Development of local partnerships, governance and system leadership arrangements to guide decision-making (OECD, 2019).
• Drawing upon repositories of evidence-based programmes (EBP) or practices that have been demonstrated through rigorous experimental evaluation to improve outcomes (Burkhardt et al., 2015;Catalano et al., 2012).However, we argue there are some important limitations or inhibitors to impact at scale for such prevention frameworks, particularly when considering the systemic nature of the social determinants of young people's mental health and wellbeing.The following critiques do not amount to a rejection of the approach, but rather point to ways they may be further optimised:

Aims and objectives
Our long-term vision is to demonstrably improve, at the local level, youth mental health and wellbeing outcomes via the design and implementation of preventative approaches that address contextually relevant social determinants of health.
Our objectives are: 1) To create a prevention framework (Kailo) that: 2) To implement this framework in two distinct geographical contexts, and through practice-based learning and developmental evaluation seeking to explore what works, for whom, under what circumstances, and how (Wong et al., 2016); 3) Incorporate learning into a refined, replicable and locally owned framework that is adopted in new contexts and evaluated for impact on population-level mental health and wellbeing outcomes.
These objectives are underpinned by the following research questions: • RQ1: How does Kailo function as an initiative?Why and for whom?
• RQ2: How is Kailo received in a local context and what conditions are necessary for place-based systems change to be achieved through Kailo?
• RQ3.What is the impact of Kailo, in relation to the alignment and coordination of local resources and systems of support (and how does this vary by context)?
• RQ4.What is the impact of Kailo in relation to young people's mental health and wellbeing outcomes and associated inequalities (for whom, and how does this vary by context)?
• RQ5.What is required in order to effectively scale the Kailo framework?

Kailo Framework
Kailo is a prevention framework designed to help local community and public system partnerships elevate the voice of young people in designing systemic, evidence-informed strategies and interventions that systemically address the social determinants of young people's mental health and wellbeing in the local context.
Kailo is a framework that operates across three main phases: 1. Early Discovery: including building strong and trusted local partnerships, understanding what matters locally, and community forming around shared priorities.

Deeper Discovery and Co-Design:
A structured method of youth-centred co-design that takes a systemic, equitable and evidence-informed approach.
3. Prototyping, Implementation and Testing: A process of embedding designs into local infrastructures and iteratively testing and refining them.
Within each phase is a series of tools and structured research and design activities (see Table 1).These include system mapping methods, co-design, data (through existing administrative and new local epidemiological data) and different forms of evidence (practice-and lived experience evidence alongside rapid reviews of existing research and robust evaluations).
Implementation of the Kailo Framework and the activities described in Table 1 are underpinned by a set of guiding principles for those implementing it: • Working collaboratively with the people and communities that will be impacted; • Adding value and building capabilities, rather than being extractive or burdensome; • Recognising bias and inequalities and striving to reduce them; • Making space for reflection and learning throughout.
The integration of these principles and different sources of insight and knowledge through a systemic lens is intended to inform a contextually nuanced set of intervention points and local priorities with potential for impact.In turn, evidenceinformed co-design approaches are hypothesised to result in a coordinated portfolio of high-leverage local interventions that, in turn, will lead to intermediate community-based outcomes and longer-term improvements in adolescent mental health and wellbeing (by addressing the locally relevant social determinants of health).

Audiences and roles
The Kailo Framework is primarily intended for use by local authority and integrated health partnerships (such as Integrated Care Partnerships in England, or Health and Social Care Partnerships in Scotland) working in partnership with local communities.The framework and phases are designed to gradually shift ownership of the work in a local area from a facilitating Kailo team to the local community partnership (as illustrated in Figure 1).This relates to one of the underpinning principles (i.e., to add value and build local capabilities).
Understanding, prioritising, co-designing and testing local responses to the social determinants of young people's mental health is a complex task, requiring a wide range of activities -as illustrated in Table 1.Kailo is designed as a 'modular' approach in that different activities may be undertaken (or may have already been undertaken) in a local area in different ways by different local stakeholders or actors, to varying degrees of intensity or depth.Kailo acts as a framework or guide to prioritising, designing and testing local approaches to the social determinants of young people's mental health and wellbeing, with an accompanying set of tools and methods which can be adopted as required.
It is our hypothesis that each element is required, and that the rigour and depth of each stage will be associated with greater buy-in and likelihood of impact, but that all stages need not necessarily be led by a central Kailo team.For example, if  Evaluation framework and Kailo v2.0It is intended that insights from early implementation and the developmental evaluation of v1.0 of the Kailo Framework in the two pathfinder areas will inform a refined version of the framework (v2.0) that can be implemented in additional sites.These learnings will also inform wider replication and the subsequent contributory impact evaluation to assess how the framework contributes to improvements in adolescent mental health, changes in the wider social determinants, and local shifts in commissioning practices.
Given the complexity of the Kailo Framework, a developmental realist-informed evaluation will be conducted in the two pathfinder sites (Kennedy et al., 2023, in preparation).This evaluation will move beyond the binary question of effectiveness (Raine et al., 2016) and seek to explore what works, for whom, under what circumstances, and how.
As such, a developmental realist-informed evaluation will be conducted (Pawson & Tilley, 1997;Westhorp, 2014).This will investigate how and why Kailo works, for whom, and under what circumstances.This mixed-methods evaluation will engage key members of the Kailo consortium, local stakeholders, and young people who have interacted with Kailo in the pilot sites.The initial phase incorporates a rapid realist synthesis, interviews with key informants, observations, and document analyses to formulate the initial programme theory (Jagosh, 2019;Manzano, 2016).The second phase will employ semi-structured interviews, focus group discussions, observations, and analyses of routinely collected data to test the initial programme theory (Manzano, 2022).The final phase will employ focus group discussions to refine and consolidate the initial programme theory (Shearn et al., 2017).
The developmental nature of this evaluation will facilitate sharing of feedback to improve programme implementation and support continuous learning and adaptation (Gamble, 2008).
As the Kailo framework matures and is scaled to new sites, a summative impact evaluation will be designed and implemented, addressing research questions related to impact on sub-group and local population-level outcomes and inequalities.

Inherent tensions, anticipated and early challenges and how Kailo is responding
In this section, we outline six key anticipated challenges, some of which are being experienced in the early stages of implementation, and how Kailo is responding.
First, there has been a legacy of national and local reorganisation and change initiatives that are not sustained.It is commonplace in local government and community partnerships for there to be history of change and reorganisation, which may not lead to tangible or observed change to community outcomes or experience (Alderwick et al., 2022).Kailo, as another initiative, risks perpetuating such change fatigue.As such, the principle of adding value is critical.Rather than acting as another initiative on top of others, Kailo is positioned in local areas as feeding into and bolstering existing initiatives and policy directives.This may include seeking to build capacity, resources and precision to hotspots of pre-existing community-based practice, social action and alliances (where sufficiently aligned), as well as integrating priorities and emerging designs into local strategies and existing governance arrangements.
Second, early experiences of implementation of the Kailo framework suggest a strong pull from senior leaders and commissioners towards focusing on service and treatment responses -the status quo -rather than a preventative focus centred on the social determinants of mental health (Mc-Daid & Park, 2022).This is particularly expressed from public system leaders, commissioners and practitioners, albeit much less so from young people and community partners and representatives.To mitigate against this risk, in most of our communications, articulation of aims and interactions in local areas, we consistently and routinely emphasise the intentional focus on prevention and the social determinants of young people's mental health and wellbeing (Faust & Menzel, 2011;World Health Organisation: Department of Mental Health and Substance Dependence, 2002 ).We are also at pains to communicate this is not to say that further coordination and investment in treatment services is not critical, but that this is not the role for Kailo (although insights and learning from early discovery phases can support and make the case for such investments).
A third tension is the systemic focus of Kailo, the iterative and emergent approach to discovery and co-design (Pailthorpe, 2017), and the evaluative frame of considering contribution in relation to context (oftentimes at odds with positivist causal assumptions and attribution) (Nyein et al., 2020).These tensions are expressed less-so in local communities, but more so within the academic and research contexts (as well as within our own multi-disciplinary research consortium).This speaks to wider debates in the field about what types of evidence are valued (Glasgow & Emmons, 2007;Rycroft-Malone et al., 2004).
Fourth, as introduced above, is the tension in considering what types of evidence are valued, by whom, and in what contexts (Beames et al., 2021).It is not uncommon for lived/living experience, youth and community voice to be considered less rigorous, valuable or at odds with other forms of evidence, such as quantitative data or more generalised evidence (O' Leary & Tsui, 2022).Within Kailo we are seeking to break down such false divides, through generating and surfacing different sources of insight and viewing points on specific issues in different ways, that are proportionate and appropriate to the specific questions being explored.For example, youth and community voices can explore and challenge the generalisability of existing evidence to local context, whereas existing research evidence may challenge poorly substantiated beliefs and help strengthen emerging intervention designs (based on what has been tried and tested elsewhere).It may be that different sources of insight and evidence can be aligned and reconciled, or it may transpire that they are in more fundamental opposition.Yet what Kailo seeks to advance a dialogue between multiple 'positions' in order to advance at least a shared understanding and respect of these different viewing points so that 'epistemic trust' and an openness to differing sources and forms of knowledge, insight and learning may be built (Fricker, 2007;Schröder-Pfeifer et al., 2018;Tuomela, 2007).
Fifth, we anticipate ongoing tensions in relation to where decision-making power resides, and how such power is shared or transferred (Joseph-Williams et al., 2014).Typically, power and decision-making for setting regional and local priorities, strategies and associated resource allocation sit with senior leaders within public systems (often with wide and geographically distributed remits).This inevitably means that decision-making may not closely reflect a nuanced understanding of needs, contexts and what matters locally (Seixas et al., 2021).Conversely, grassroots, youth or community-based designs may be removed or disconnected from the policy, fiscal and commissioning constraints.This speaks to the need to better connect and bridge local public system decision-making and design with the assets, insights and power that resides within local communities (Local Government Association and NHS Clinical Commissioners, 2020).This is something we are attempting to do with Kailo, and the way in which 'small circle' co-design teams are nested within 'big circles' of community and public system leadership.Our early implementation experiences suggest how critical it is to carefully nurture and connect local relationships and build trust within and between different stakeholder groups -something echoed in wider research (Frerichs et al., 2017;Metz et al., 2022;Vangen & Huxham, 2003;Wilkins, 2018;).
Finally, as we embark on the co-design phases of the Kailo Framework, we anticipate tensions and challenges in relation to responsible, embedded and sustainable design (Goodyear-Smith et al., 2015)-which relates to the first tension about change or initiative fatigue.Given the highly constrained economic climate (The Health Foundation, 2022), it is necessary and essential that what gets designed locally can be implemented and sustained within existing and available local resources and assets -be these financial, human (e.g., through existing workforces) -or within existing infrastructures (physical/environmental, economic or social).
Subsequent papers and results from the developmental and realist evaluation will report on further learning, findings and how the Kailo Framework evolves.

Open Peer Review
Current Peer Review Status: Overall, it provides an overview of an innovative and relevant approach which highlights crucial issues as working with local partners and involving young people in systems change activities when supporting and delivering preventative interventions and changes for mental health that address social determinants.

Background
Need and inequalities -The references and sources provided in the first two paragraphs of the Needs and inequalities section are England/UK (and one EU) focused, We think it would be helpful to clarify that the statements given specifically relate to the area cited (e.g.UK/England/EU).Or if the authors wish to make a more generic statement, we suggest to seek international references to support their statement (especially in the second paragraph).
-If space allows, it would benefit us to know which aspects of mental health the authors would like to address (perhaps by a definition of mental health and wellbeing or at minimum highlight that it is all mental health conditions and wellbeing that Kailo is concerned about, and/or that outcomes will be co-determined with young people and local partners (for example)).
Existing frameworks for understanding local needs and guiding prevention efforts -"These prevention frameworks have, in some contexts, demonstrated positive impacts on outcomes (Brown et al., 2011;Crowley et al., 2011;Oesterle et al., 2018;Spoth et al., 2017)."-please can the authors specify on which outcomes there was an improvement and whether these effects were sustainable.At minimum we would recommend the authors highlight that it is "some" outcomes, as the references cover mainly substance use and knowledge outcomes.It may also be helpful to mention the specific positive impacts in each citation (e.g.

Accessibility
-Where possible, providing definitions to concepts introduced in the manuscript would support the reader's understanding and would ensure this article is accessible to a wider audience.This includes concepts mentioned, such as: "place-based", "power mapping", "design thinking ideation", "epistemic trust" and "summative impact evaluation".
-Regarding summative impact evaluation it may be helpful to add some examples / definitions of approaches used and how such an impact evaluation may be co-designed.
-Some wording in the abstract could be simplified, for instance this sentence could be shortened: "…manifest or may be influenced at the local level, impeding the design of contextually nuanced preventative approaches"

Abigail Thomson
Centre for Psychiatry and Mental Health, Queen Mary University of London, London, England, UK This paper introduces Kailo, a novel prevention framework designed to support local community and public system partnerships to design and implement local and contextually nuanced preventative strategies to improve children's and young people's mental health and wellbeing.
The authors provide a strong rationale for their framework, highlighting several limitations of current mental health treatment and research for young people, noting an overreliance on monocausal assumptions and narrowly defined health outcomes.They frame young people's mental health and well-being as a 'systems issue', emphasising the role of wider and interacting social determinants.Further, they suggest that despite advancements in treatment responses, issues with funding, resources and capacity hamper these efforts and exacerbate inequality in access to mental health support (a crucial social determinant of population mental health).The authors describe the need for a more nuanced local perspective, exploring how the social determinants of mental health are manifest at the micro level, in addition to considering macro-systemic influence (e.g.poverty, housing).Further, they describe the need for better preventative support that more meaningfully elevates youth and community voices and balances evidence-informed practice with local innovation and co-design.Greater consideration could be given here to those groups of young people who are most underserved by current approaches, whose voices are underrepresented, and for whom the 'systems' described may have a greater impact on their mental health and well-being.
Overall, the Kailo Framework is described as aiming to improve, at the local level, youth mental health and wellbeing outcomes via the design and implementation of preventative approaches that address contextually relevant social determinants of health.It is described as operating across three phases: (i) Early Discovery -building local partnerships and shared priorities (ii) Deeper discovery and Co-Design -youth-centred co-design methods (iii) Prototyping, Implementation and Testing -embedding designs into local infrastructures.The framework's modularity and flexibility are highlighted, alongside the importance of evaluation and future development.The authors could consider describing how their approach plans to better serve the many small and successful community health projects that operate under the radar of formal evaluations and those that are dynamic by nature (i.e.participatory methods) where changes often occur long after formal evaluation.
The initial and anticipated challenges of the Kailo framework are well considered, and the authors outline some of the steps needed going forward to address these challenges.Attention is given to understanding how different types of evidence manifest within a local and community context and how this may be at odds with current recognised approaches.Further discussion could be given around plans to address this, beyond developing a shared understanding, particularly for those stakeholders or community partners most impacted by systemic inequalities that are contributing their voice to the project.

Is the rationale for the
a) Helps local public system and community partnerships better understand how the social determinants of young people's mental health and wellbeing manifest at the local level; b) Elevates youth and community voice in determining priorities for change; c) Highlights inequalities in experiences and outcomes as a focal point for change; d) Brings young people, community partners and professionals together in co-designing systemic and evidence-informed strategies to address these social determinants, inequalities and improve young people's mental health and wellbeing; and e) Integrates these priorities and designs into local strategic planning and commissioning to enable sustained change.

Figure 1 .
Figure 1.Shifting ownership of Kailo over phases.This image demonstrates how the Kailo team hopes to shift their role through the different phases of the Kailo Programme.The Kailo Community (blue), which includes local community members and young people, should become the main drivers of the Kailo programme locally, with the support of the Kailo team that initially was steering the project.
doi.org/10.21956/wellcomeopenres.22254.r73611© 2024 Reardon T. This is an open access peer review report distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Tessa ReardonDepartments of Experimental Psychology and Psychiatry, University of Oxford, Oxford, England, UKThe authors present a convincing case for the need for systemic approaches that address the social determinants of young people's mental health and wellbeing at a local level.They clearly articulate the implications of focusing only on treatment at the expense of preventive efforts, and the need to consider the complex, interconnected influences on mental health and how this varies across contexts.Limitations with existing prevention frameworks are presented, including limitations related to underpinning data, the absence of young people's voices, and neglecting local practice and innovation.The paper moves on to present aims to create, implement and refine the Kailo prevention framework that seeks to address limitations with previous frameworks.The guiding principles of Kailo, together with inputs, activities, intended outcomes and indicators of success across three phases of the programme are clearly spelled out.An overview of initial evaluation plans is provided and expected challenges and responses helpfully discussed.It may help to clarify how evaluation is considered in the early phases of the programme.For example, does co-designing systemic responses incorporate co-designing evaluation of these responses?Adolescent mental health outcomes are mentioned in later parts of the paper -it would help to clarify and specify earlier in the paper if the initiative focuses on a specific age range.Is the rationale for the Open Letter provided in sufficient detail?YesDoes the article adequately reference differing views and opinions?YesAre all factual statements correct, and are statements and arguments made adequately supported by citations?Yes Is the Open Letter written in accessible language?Yes Where applicable, are recommendations and next steps explained clearly for others to follow?Yes Competing Interests: No competing interests were disclosed.Reviewer Expertise: child mental health; school-based interventions I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.Reviewer Report 25 May 2024 https://doi.org/10.21956/wellcomeopenres.22254.r69990

Table 1 . Describes the different stages of the Kailo programme, their aims, activities, intended outcomes and indicators of success. Phase Aim Inputs and Prerequisites Activities Intended Outcomes Key Indicators of Success EARLY DISCOVERY
Playbacks:(a)sharing back emerging themes and learning;(b) iterative refinement and validation(Santana de Lima et al.,   2023, unpublished report).Prioritising Opportunity Areas:(a) focus groups; (b) voting (or Delphi or nominal group technique(McMillan et al., 2016).Co-design Team Formation:(a) formation of youth and community 'small circle' codesign teams(McKercher, 2020,  pp.1-225);(b) mutual value agreements; (c) building trust and relationships (Clarke et al., 2021).Deeper systemic Discovery: (a) refinement of Opportunity Area definition; (b) participatory group model building (Siokou et al., 2014); (c) identification of systemic intervention or leverage points (Glenn et al., 2020).Evidence Reviews: (a) Production of evidence briefings; (b) rapid realist review (Saul et al., 2013); (c) Youth and Community Research into topic areas (McCabe et al., 2023).
Oesterle et al. (2018) found a reduction in substance use, antisocial behaviour and violence, whereas Crowley et al. (2011) found increases in expert knowledge of evidence-based interventions).

Is the rationale for the Open Letter provided in sufficient detail? Yes Does the article adequately reference differing views and opinions? Yes Are all factual statements correct, and are statements and arguments made adequately supported by citations? Partly Is the Open Letter written in accessible language? Partly Where applicable, are recommendations and next steps explained clearly for others to follow? Not
Breedvelt: Mental health prevention, children and young people's mental health.Arya: Young people's perspectives on preventative interventions, mental health prevention, children and young people's mental health applicable Competing Interests: No competing interests were disclosed.Reviewer Expertise:

We confirm that we have read this submission and believe that we have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however we have significant reservations, as outlined above.
This is an open access peer review report distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Open Letter provided in sufficient detail? Yes Does the article adequately reference differing views and opinions? Yes Are all factual statements correct, and are statements and arguments made adequately supported by citations? Yes Is the Open Letter written in accessible language? Yes Where applicable, are recommendations and next steps explained clearly for others to follow? Yes Competing Interests:
No competing interests were disclosed.Community-based participatory research; Youth engagement/involvement in mental health research; Community-based implementation; Digital interventions; Transdiagnostic approaches to treatment/prevention of adolescent psychopathology I

confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard. References
1. Menear M, Blanchette MA, Demers-Payette O, Roy D: A framework for value-creating learning health systems.Health Res Policy Syst.2019; 17 (1): 79 PubMed Abstract | Publisher Full Text

Is the rationale for the Open Letter provided in sufficient detail? Yes Does the article adequately reference differing views and opinions? Yes Are all factual statements correct, and are statements and arguments made adequately supported by citations? Yes Is the Open Letter written in accessible language? Yes Where applicable, are recommendations and next steps explained clearly for others to follow
? YesCompeting Interests: No competing interests were disclosed.Reviewer Expertise: Clinical and health services research in child and youth mental health; youth, family and community engagement I confirm that I