TOPLINE:
Exposure to higher levels of green spaces (“greenness”) was associated with a decreased risk for hospital admissions for mental health disorders compared with low exposure, particularly in urban areas, a new multinational time series study showed. The association was strongest for hospitalizations for substance use disorders, psychotic disorders, dementia, and anxiety.
METHODOLOGY:
- This time series analysis included 11.4 million hospital admissions for mental disorders from 2000 to 2019 across seven countries: Australia, Brazil, Chile, New Zealand, Thailand, South Korea, and Canada. More than 60% of individuals were aged 20-59 years.
- Primary diagnoses responsible for hospital admissions included psychotic disorders (31%), substance use disorders (25%), mood disorders (12%), behavioral disorders (7%), dementia (3%), and anxiety (2.5%).
- Greenness was quantified using the normalized difference vegetation index (NDVI), with very low values (≤ 0.1) indicating barren areas, moderate values (0.2-0.5) indicating sparse vegetation, and high values (≥ 0.6) indicating dense vegetation.
- Outcomes included the associations between exposure to greenness indicated by the NDVI values and cause-specific or region-specific mental health admissions.
TAKEAWAY:
- A 0.1-unit increase in the vegetation index was associated with a 7% lower risk for hospital admissions for all-cause mental disorders (relative risk [RR], 0.93; 95% CI, 0.89-0.98). Protective associations were strongest for substance use disorders (RR, 0.91), psychotic disorders (RR, 0.93), dementia (RR, 0.94), and anxiety (RR, 0.97).
- In urban settings, greenness was linked to a 13% reduced risk for hospital admissions for all-cause mental disorders (RR, 0.87), and nearly 8000 admissions annually were deemed potentially preventable with greater greenness exposure.
- Region-specific risk for hospital admissions was lowest for Thailand (RR, 0.79) and highest for Australia (RR, 0.99).
- The annual number of hospital admissions for all-cause mental disorders associated with exposure to greenness was 1213 in New Zealand, 20 in South Korea, 605 in Thailand, 719 in Canada, 4677 in Brazil, 328 in Chile, and 150 in Australia.
- A 10% increase in greenness was associated with a decrease in mental health-related hospital admissions and ranged from approximately 1 per 100,000 in South Korea to 1000 per 100,000 in New Zealand.
IN PRACTICE:
“A considerable proportion or rate of hospital admissions for mental disorders may be associated with exposure to greenness and could potentially be reduced through greening interventions under realistic scenarios,” the investigators wrote.
“These mental health benefits may also bring broader economic and social advantages, including reduced healthcare costs, less strain on health systems, improved workplace productivity, and enhanced community wellbeing,” co-investigator Yuming Guo, Monash University, Melbourne, Australia, said in a press release.
SOURCE:
This study was led by Tingting Ye, School of Public Health and Preventive Medicine, Monash University, Melbourne, Australia. It was published online on November 05 in BMJ.
LIMITATIONS:
Data sourced from multiple countries may have introduced uncertainties due to differences in the management of mental health systems. The study captured only severe mental health conditions requiring inpatient care, excluding milder, subclinical, or untreated cases managed in outpatient or community settings. Additionally, the NDVI does not account for qualitative aspects such as access, safety, or biodiversity.
DISCLOSURES:
This study was funded by the Australian Research Council and Australian National Health and Medical Research Council. The investigators reported no relevant conflicts of interest.
This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.