As part of the larger Green Social Prescribing (GSP) Test and Learn Pilots extension project, we are carrying out a feasibility study to understand and characterise the best experimental or quasi-experimental study design, with nested pilot, process evaluation and cost effectiveness/utility analyses, to assess the effectiveness of GSP pathway(s) and establish what is appropriate, useful, and feasible from methodological and policy/practitioner/patient perspectives.

There are several key challenges in designing studies to evaluate the effectiveness of GSP that we want to address:

The need for clear evidence on GSP effectiveness

We need to better understand where to focus our efforts in collecting evidence on how effective GSP is, particularly in terms of cost-effectiveness. It is unclear whether we should be looking at how well GSP works in ideal conditions (efficacy), or in real-world settings (effectiveness). It is also not certain which GSP pathways – such as whether people get referred through a link worker or refer themselves – are key to explore, in order to gather the best evidence for decision-makers. We also do not know enough about the different ways people access GSP, which makes it hard to generalise findings.

Complexity of GSP pathways

GSP involves several interconnected parts: initial referral (from a GP or mental health services, or self-referral), consultation with a link worker, and the activities prescribed. Each of these parts can affect whether GSP benefits someone. Because GSP is complex, it is challenging to design studies that can accurately assess its overall effectiveness. We need to decide how much we should standardise each part of GSP and ensure we have the right measures to assess its impact.

Challenges in choosing control croups

It is difficult to find suitable control groups for studies on GSP. Control groups are necessary to compare the effects of GSP against other activities or treatments. However, because GSP has multiple components and ways people can enter the programme, including patient choice, finding an appropriate control group is not straightforward. If we do not choose the right control group, this could undermine the study results. There are also ethical concerns around withholding GSP from the control group, which might affect the trial’s practicality and reliability.

Randomisation and study design issues

Randomising participants in GSP studies is challenging because taking away patient choice can conflict with how GSP is supposed to work. Deciding when and how to randomise participants is particularly difficult given the multiple pathways into GSP. This also complicates other aspects of study design, like analysing the data. Additionally, we need to carefully select which groups of people to study, making sure they are relevant to both policy and practice. This selection will influence the study’s outcome measures and design, including the sample size and support needed for vulnerable participants.

Methods

We will carry out the foundation work for a definitive trial with nested pilot, process evaluation and cost effectiveness/utility analyses of GSP that includes a referral pathway component, aiming to address the RCT uncertainties listed above. The steps we will take are numbered and follow the guidance on development of experimental designs for complex interventions. Patient and Public Involvement work will be coordinated by a specialist in public and patient involvement.

Workshops

To help clarify the best study design, we will hold three workshops with key stakeholders across a selection of differing sites (e.g. urban/rural, established/developing GSP). Stakeholders will include commissioners, policy makers (including NHSE, DHSC, Defra), NASP, link workers, activity providers, and methodological experts. We will aim to recruit approximately 10 participants per workshop. Interviews will be held with key informants unable to join a workshop.

Workshop topics will include:

• Which pathway(s) are key to understand (e.g. primary care, mental health, community, self-referral etc).

• Which populations should be targeted.

• Which comparisons should be made (establishing GSP as effective compared to what?).

• Key outcomes.

• Which study designs are valued/needed by stakeholders when making policy, funding and practice decisions on GSP.

We will be scheduling these workshops to take place in October 2024. If you have any questions, please contact Helen Eke at h.e.eke@exeter.ac.uk.