OBJECTIVES: Loneliness is a significant public health concern with negative effects on physical and mental well-being. An upcoming approach to alleviate loneliness is called nature-based social prescribing (NBSP). We aim to study the social value generated by an investment in NBSP interventions.

METHODS: Based on a systematic review and expert meetings, we searched for a method and established guidelines on how to consider social, environmental, and economic impacts of NBSP beyond financial effects complementing our related cost-effectiveness along the trial and decision-analytic modeling study conducted within the EU-project RECETAS.

RESULTS: We decided to perform a Social Return on Investment (SROI) study within our RCTs to quantify the social value generated by each Euro invested. Following key principles and stages, stakeholder identification, outcome mapping, and outcome measurement were performed following the RECETAS logic model. Identified stakeholders are participants, care providers, voluntary and community sector organizations (VCSO), volunteers, and the national healthcare system (NHS). Outcomes for participants are loneliness and health-related quality of life collected during the RCTs. The participants’ outcomes extend to care providers, as improved population health reduces the burden on the stretched NHS. VCSOs benefit, as it would increase utilization of resources. Volunteers experience improved life satisfaction caused by volunteering. The NHS experiences a relevant change in medical resource use. Next, a SROI considers the stakeholder’s outcome measurement to provide outcomes with a financial value if a material change is observed in the RCTs. Financial proxies will be retrieved from the Social Value Bank, such as GBP1,850 /participant/year for reduced loneliness through social group membership.

CONCLUSIONS: The SROI approach quantifies the total social value of NBSP interventions once RECETAS trial results are available. The SROI ratio can be calculated by dividing the social value by the total costs. Engaging stakeholders and experts from the RECETAS trials will validate and support the study's quality.