Background
Green social prescribing is a means of connecting people with non-clinical, nature-based interventions, often delivered by third sector organisations using local community assets. Community-led interventions that support well-being could help alleviate increasing pressure on mental health services. There is a need, however, to demonstrate their social cost-benefit to support the integration of green social prescribing into policy and practice.

Here we present a mixed-method Social Return on Investment (SROI) evaluation of a six-month pilot ‘Making Well’ natured-based therapeutic programme of traditional crafting, horticulture, and contemplation to support people with long-term mild to moderate mental health conditions in Powys.

Methods
The ‘Making Well’ pilot project delivered two programmes between October 2021 and April 2022. Participant’s data (n=15) were collected at baseline and eight-week follow-up and interviews were conducted to collect in-depth data on their lived experience of the programme. The ‘Making Well’ programme costs were estimated and financial proxies from the HACT Social Value Bank were applied to identified benefits. Three alternative well-being valuation approaches were applied as an embedded sensitivity analysis to estimate a robust range of social value ratios.

Results
The estimated cost of Making Well programme inputs were £1,312 per participant and the net value of well-being benefits were £4,313 to £6,130 per participant, giving a range of social value ratios between of £3.30 to £4.70 for every £1 invested. Important outcomes reported by participants included experiencing higher self-confidence, increased feelings of social connection, and improved mental health.

Conclusions
This SROI evaluation demonstrates that the ‘Making Well’ programme is an effective non-clinical green social prescribing intervention for supporting people with long-term mild to moderate mental health conditions. The research contributes to emerging social cost-benefit evidence for the social prescribing of community-led, nature-based interventions.