Associations of green and blue space and the natural environment with suicidal ideation: the role of psychiatric disorders

Background: Previous research has demonstrated the importance of environmental factors and exposure to the natural environment for human physical and mental health. However, the associations between green space, blue space, and the natural environment (GBN) and the risk of suicidal ideation have not been prospectively studied, and the potential role of psychiatric disorders in these associations has not been explored.

Methods: Longitudinal data from the UK Biobank was used. At study baseline (2006-2010), 135,901 participants (female: 56.6%; mean age 56.05±7.73 years) were included. A series of binary logistic models were used to examine the independent, joint, and interactive associations of GBN and psychiatric disorders with suicidal ideation.

Results: Compared with the first quartile (lowest) of exposure, the natural environment at 300 m buffer [Q2, OR = 0.899, 95% CI: 0.835-0.968; Q3, OR = 0.897, 95% CI: 0.831-0.968] and blue space at 1000 m buffer [Q3, OR = 0.920, 95% CI: 0.853-0.993] were significantly associated with lower risk of suicidal ideation. Green space (the fourth quartile) and the natural environment (the fourth quartile) at 1000 m buffer had 14.5% and 15.2% decreased risk of suicidal ideation, respectively. The lowest risk of suicidal ideation was observed among participants with high levels of GBN and no psychiatric disorders, which may be attributed to significant multiplicative and synergistic interactions.

Conclusions: Our findings emphasized the significant benefits of GBN exposure in reducing the risk of suicidal ideation, especially in groups with psychiatric disorders. Future research is necessary to conduct to explore potential mechanisms.