Mental health benefits of neighbourhood green space are stronger among physically active adults in middle-to-older age : evidence from 260,061 Australians

Objective: While many studies report that green spaces promote mental health, some suggest the psychological benefits of physical activity are amplified if participation occurs within greener environs. We investigated whether this relationship could be observed among adults in middle-to-older age. Method: Multilevel logit regression was used to investigate association between green space and psychological distress (Kessler scores of 22. +) among 260,061 Australians over 45. years old living in New South Wales (2006-2009). Physical activity was measured using the Active Australia survey. Percentage green space was estimated within a 1-kilometre of residence. Results: In comparison to residents of the least green areas, those in the greenest neighbourhoods were at a lower risk of psychological distress (Odds Ratio 0.83, 95% CI: 0.76, 0.92) and were less sedentary (0.81: 0.77, 0.87). An interaction was observed between physical activity and green space (p= 0.0028). More green space did not appear to benefit mental health among the least active (0.99: 0.85, 1.15), but there was a protective association for the more physically active (0.82: 0.67, 0.99). Conclusion: For adults in middle-to-older age, green spaces are not only important for promoting physical activity, but the mental health benefits of greener environs appear contingent upon those active lifestyles.