Green space, blue space and psychological distress in regional Australia: Cross-sectional and longitudinal analyses

Evidence on the relationship between green and blue spaces and mental health in regional areas of Australia is limited. This study assessed associations between green space, blue space, green-blue space (GBS), and psychological distress in regional Australia, and examined effect modification by age, remoteness, and socioeconomic disadvantage. Using cross-sectional and longitudinal data from Waves 17 (2017) and 21 (2021) of the Household, Income, and Labour Dynamics in Australia (HILDA) Survey, we analysed data from 5186 adults at baseline and 3146 at follow-up. Psychological distress was assessed using the Kessler Psychological Distress Scale. Green space and GBS were quantified as percentage coverage, and blue space was classified as present or absent in the residential environment. Generalized Estimating Equation models were used to assess associations, and stratified analyses were conducted by age, geographic remoteness, and socioeconomic disadvantage to examine potential effect modification. At baseline, no statistically significant associations were found between green space, blue space, or GBS and psychological distress. GBS cover of 11-20 % was associated with a 34 % lower incidence of psychological distress at follow-up (OR = 0.65, 95 % CI: 0.45, 0.95). In stratified analyses, green space cover of 11-20 % (OR = 0.55, 95 % CI: 0.34, 0.89) and GBS cover of 11-20 % (OR = 0.48, 95 % CI: 0.29, 0.79) were associated with reduced psychological distress at baseline in the most socioeconomically disadvantaged areas. Additionally, GBS cover of 21-40 % was associated with a lower incident psychological distress in outer regional areas (OR = 0.56, 95 % CI: 0.31, 0.99). These findings suggest that green space and GBS may mitigate psychological distress, particularly in socioeconomically disadvantaged areas, highlighting their potential to support mental health and reduce health inequalities.