Abstract
<title>Abstract</title> <p> <bold>Background:</bold> Mental health disorders, and a lack of access to adequate mental health care, disproportionately affect marginalized groups, leading to health inequities. Growing scientific evidence shows that nature-based therapies (NBTs) can improve adult mental health and wellbeing. However, less is known about how NBTs may impact health equity at the population level. We aimed to develop a theory-of-change (ToC) informed by a diverse group of NBT stakeholders to better understand the mechanisms by which NBTs may improve adult mental health and wellbeing equity. <bold>Methods:</bold> We used a two-stage eDelphi approach to elicit knowledge about how NBTs work and the contextual factors that influence whether an NBT is effective in improving adult mental health and wellbeing equity. Respondents were researchers, NBT practitioners, and policy makers from the Global North. Participants first answered open questions structured around the ToC components and identified definitions, enablers and challenges influencing who benefits from NBTs. After creating a list of unique responses organized by ToC component, respondents were then asked to rate each response in terms of importance and relevance. Final agreement scores were calculated and the final ToC was informed by those statements on which respondents agreed were both important and relevant. <bold>Results:</bold> Respondents conceptualize NBTs as having potential positive impacts at the individual and population levels, including improved environmental awareness and resilience and social cohesion. Respondents identified pathways operating at individual, community, and system levels, highlighting accessibility, facilitator training, public funding, and healthcare integration as key determinants of equitable benefit. Respondents agreed on several key challenges which may preclude NBTs from benefiting all population groups including misconceptions among healthcare providers and potential beneficiaries and a lack of recognition of NBTs as a legitimate form of healthcare, as well as more tangible challenges such as accessibility and funding. <bold>Conclusions:</bold> Despite diverse expertise and cultural backgrounds, respondents reached strong agreement on the pathways by which NBTs are understood to improve adult mental health, wellbeing, and equity. Further, NBTs face several challenges that preclude them from reaching their full potential in terms of impact on mental health and wellbeing equity. </p>