Does physical activity mediate the associations between blue space and mental health? A cross-sectional study in Australia

BACKGROUND: Research has begun to examine whether blue space is beneficial to mental health. While results are promising, it is difficult to know which aspects of mental health or mental ill-health may benefit most. Physical activity has been proposed as one potential mechanism via which blue space may be associated with better mental health. However, very few studies have examined mechanisms. We examined associations between blue space proximity and a range of mental health outcomes and examined which of these associations were mediated by physical activity. METHODS: 350 participants (M = 38.74, SD = 14.92, 70% female) self-reported their weekly physical activity and completed measures of depression, anxiety, and psychological wellbeing. We then used GIS software to calculate blue space proximity (i.e., coastal and inland), and structural equation modelling with mediation paths to determine the role of physical activity in the associations between bluespace and mental health. RESULTS: Physical activity partially mediated the associations between coastal proximity and depression (β = 0.02, 95% CI = 0.001, 0.05), anxiety (β = 0.03, 95% CI = 0.01, 0.06), and wellbeing (β = − 0.03, 95% CI = − 0.08, − 0.01), and fully mediated the associations between inland water proximity and depression (β = 0.02, 95% CI = 0.003, 0.05), anxiety (β = 0.03, 95% CI = 0.01, 0.07), and wellbeing (β = − 0.03, 95% CI = − 0.07, − 0.01). CONCLUSION: While physical activity appears to explain associations between inland blue space and mental health outcomes, it only partially explains the association between coastal blue space and mental health, suggesting other mechanisms may play a role and even inactive exposure may be beneficial.