Study finds that green environments are associated with lower risk of depression and anxiety

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In a prospective cohort study published in the journal natural mental health, Researchers in China investigated the potential link between exposure to green residential areas and the development of anxiety and depression, and investigated the underlying pathways. They found that extended stays in green environments were associated with a lower risk of depression and anxiety, potentially via air pollution.

Research: Long-term exposure to residential greenery reduces risk of depression and anxiety. Image credit: p-jitti / ShutterstockResearch: Long-term exposure to residential greenery reduces risk of depression and anxiety. Image credit: p-jitti / Shutterstock

background

Mental disorders such as depression and anxiety are among the most debilitating conditions and their impact on the global health burden is steadily increasing. These disorders affect millions of people worldwide and are influenced by genetic, behavioral, and environmental factors. Recognizing modifiable factors associated with mental health problems may provide valuable targets for intervention and inform potential treatment strategies.

There is now growing evidence that greening the home is an important environmental factor that reduces stress and improves health, especially mental well-being. Several longitudinal studies suggest a negative association between green space and depression, but inconsistent results suggest that larger, well-designed studies should be conducted to better understand this relationship. This highlights the need for prospective cohort studies. Long-term exposure to green has been hypothesized to provide cumulative mental health benefits through a variety of pathways, but population-based evidence is lacking and the main mechanisms remain unclear. . In the current cohort study, researchers investigated the association between long-term exposure to residential greenery, depression, and anxiety, examining potential pathways and factors.

About research

Data from 409,556 participants were obtained from a large prospective cohort, the UK Biobank. The median age of participants was 58 years, and 52.4% were female. Approximately 90.8% of participants were white and 86.2% lived in urban areas. Participants provided detailed information through questionnaires, physical measurements, and biological samples. The analysis focused on the association between green homes and the incidence of depression and anxiety, excluding people with mental health problems. A subset of participants was analyzed to explore potential pathways. The mean follow-up period was 11.9 years.

Greenness around residential areas is determined using NDVI (Normalized Difference Vegetable Index), a measure based on ground surface reflectance of infrared wavelengths within buffer areas of size 300 m, 500 m, 1,000 m, and 1,500 m. It was evaluated. Data were obtained from medium-resolution imaging spectroradiometer remote sensing. Preprocessing was performed to remove cloudy and snowy areas and address the effects of water bodies. Diagnoses of anxiety or depression at baseline and follow-up were ascertained using hospital admissions, death registries, primary care records, and self-reports verified by health professionals. Cases were identified using International Statistical Classification of Diseases and Related Health Problems (ICD-10) codes.

The analysis included socio-demographic factors (age, gender, ethnicity, income, education, place of residence), lifestyle factors (BMI), smoking status, drinking status), environmental factors (air pollutants, noise, water rates, (e.g., urban morphometric measures). Statistical analyzes included time-varying Cox proportional hazards models, hazard ratios (HRs), restricted cubic splines, mediation analyses, subgroup analyses, and sensitivity analyses.

Results and discussion

Approximately 4.1% and 3.5% of the total participants were diagnosed with anxiety (HR = HR = 0.86) and depression (HR = 0.84), respectively, during the study period. Exposure to residential greenness consistently showed a protective effect against depression and anxiety, with significant reductions in risk observed across different buffer sizes. Mediation analysis showed that air pollution was primarily particulate matter (PM) with a diameter of 2.5 microns.2.5), no2noXSo2and O3, significantly mediated the association between NDVI and both depression and anxiety. Furthermore, IMD (abbreviation for Index of Multiple Deprivation) was found to mediate the association between NDVI and depression. In addition, factors such as distance to the coast, factories, and medical facilities, as well as lifestyle factors such as sleep duration and social engagement, also showed small but significant mediating effects. The protective effect of a green environment was found to be more pronounced on depression and anxiety in older adults and men.

Sensitivity analyzes confirmed the robustness of our main results. Large sample sizes, long follow-up periods, detailed adjustment for potential confounders, and exploration of potential mediators strengthen our results. However, this study lacks details regarding the quality of green space, the potential influence of external factors on green exposure, healthy volunteer bias, and potential bias introduced by using diagnosis rather than symptom onset. limited by what you do. Further studies are needed to confirm these findings.

conclusion

In conclusion, this is the first prospective cohort study to provide comprehensive insight into the association between green exposure and mental health. The findings reveal that long-term exposure to residential greenery is associated with a lower risk of depression and anxiety. Higher levels of ambient greenery showed a more substantial positive effect on mental health, with reduced air pollution identified as an important mediator. These findings call for strategic urban planning interventions by local governments to promote mental well-being by enhancing green spaces.

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