The impact of green exercise on mental ill-health in community populations.

Mental ill health is a global health crisis with considerable societal and individual costs. The benefits of physical activity for psychological health are well-established, however, the importance of the environmental context of physical activity is less extensively researched. Emerging evidence suggests physical activity in the presence of nature may improve psychological health, whilst helping to reduce inequalities and improving adherence to physical activity interventions. This may be particularly beneficial for individuals living with untreated symptoms of mental ill health. First, this thesis considers the effect of the physical activity environment using systematic review and meta-analysis methodologies. Second, it explores behaviour of the UK general population to identify the effect of habitual green exercise on psychological outcomes via cross-sectional survey data collected from 562 respondents. To harness the potential psychological health enhancing benefits of green exercise, Intervention Mapping was used to co-produce a rigorously designed intervention underpinned by empirical evidence, behaviour change theory and experiences of community stakeholders. Finally, the resultant 9-week intervention was tested via a mixed-methods feasibility study with 13 women recruited to the study. The findings suggest that physical activity undertaken in natural environments is more beneficial to psychological health as compared with urban environments. Further, it is found that depression and anxiety may have varying sensitivity to environmental context of physical activity. Although demographic variables are stronger predictors of depression and anxiety, green exercise may offer protective benefits. A 9-week green exercise intervention, Flourish, was developed following the Intervention Mapping protocol. Whilst the Flourish study under-recruited significantly, the results highlight the importance of developing flexible interventions that are adaptable to personal circumstances and lifestyles. Clinically significant improvements were observed for depression and anxiety scores, and it is tentatively suggested that the symptoms of mental ill health may influence pathways through which the natural environment enhances psychological health.