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RL has worked with authors of individual studies included in the review but not on the studies themselves. All other authors declare they have no competing interests.
RG conceived, obtained funding for and led the review. RL and KH screened, quality appraised, extracted data and conducted the synthesis (including initial iterations of the model). CC developed the search strategy and conducted database searches. WS-T provided graphic support and produced the final version of the conceptual framework. The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.
Action taken to enhance or conserve outdoor environments may benefit health and wellbeing through the process of participation but also through improving the environment. There is interest, amongst both health and environmental organisations, in using such activities as health promotion interventions.
The objective of this systematic review was to investigate the health and wellbeing impacts of participation in environmental enhancement and conservation activities and to understand how these activities may be beneficial, to whom and in what circumstances or contexts.
A theory-led mixed-method systematic review was used to assess evidence of effect and to identify pathways to change (protocol: http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD010351/full). Due to the multi-disciplinary, dispersed and disparate body of evidence an extensive multi-stage search strategy was devised and undertaken. Twenty-seven databases and multiple sources of grey literature were searched and over 200 relevant organisations were contacted. The heterogenous evidence was synthesised using a narrative approach and a conceptual model was developed to illustrate the mechanisms of effect. Due to the limited nature of the evidence additional higher order evidence was sought to assess the plausibility of the proposed mechanisms of effect through which health and wellbeing may accrue.
The majority of the quantitative evidence (13 studies; all poor quality and lower-order study designs) was inconclusive, though a small number of positive and negative associations were observed. The qualitative evidence (13 studies; 10 poor quality, 3 good) indicated that the activities were perceived to have value to health and wellbeing through a number of key mechanisms; including exposure to natural environments, achievement, enjoyment and social contact. Additional high level evidence indicated that these pathways were plausible.
Despite interest in the use of environmental enhancement activities as a health intervention there is currently little direct evidence of effect, this is primarily due to a lack of robust study designs. Further rigorous research is needed to understand the potential of the activities to benefit health and environment.