Greenspace interventions for mental health in clinical and non-clinical populations: What works, for whom, and in what circumstances?

With growing strain on mental health services, greenspace interventions could be a promising addition to current health and social care provisions as they have the potential to be widely accessible for people within their own communities and used alongside a variety of treatment plans. Despite promising progress in greenspace research, the underlying mechanisms and processes of greenspace interventions are still unclear. Without knowing these it is impossible to understand why programmes work and how best to replicate them. To address this gap this review uses realist methodology to synthesise the international evidence for greenspace interventions for mental health in both clinical and non-clinical populations. Forty-nine full text articles are included in the review and the underlying contexts, mechanisms, and outcomes of the interventions identified and refined into an original overriding theory under three themes of Nature, Individual Self, and Social Self. The interaction of these three factors represents a new conceptual framework for greenspace interventions for mental health and shows what works, for whom, and in what circumstances. The findings of this review are not only theoretically novel but they also have practical relevance for those designing such interventions including the provision of recommendations on how to optimise, tailor and implement existing interventions.