Understanding acute mental health effects of blue and green space exposure through experimental approaches: A scoping review from 2009 to 2024

Abstract

Background

Rapid urbanization has reduced opportunities for nature contact, exacerbating mental disorders among residents worldwide. While blue and green spaces (BGSs) are increasingly recognized for their mental health benefits, prior evidence syntheses and narrative reviews rely heavily on observational evidence. The experimental evidence on the impact of BGS exposure on acute mental health has not been sufficiently understood. This scoping review synthesizes 44 experimental studies (2009–2024) to map and characterize the experimental evidence on the acute mental health effects of short-term BGS exposure.

Methods

Following PRISMA-P and the JBI Scoping Review Methodology guidelines, we developed our protocol (https://osf.io/2tvjk/overview) and searched Web of Science, PubMed, Scopus, Embase, PsycINFO, and CNKI for experimental studies. Quality appraisal and risk-of-bias assessment tools were selected according to the study design of each article, and all included studies were evaluated for quality and risk of bias. Evidence was synthesized according to the Population, Exposure, Comparator, Outcome (PECO) framework and then integrated.

Results

The existing experimental research was geographically skewed toward Asian cities, and green spaces were more frequently examined than blue spaces. Stress (n = 30), perceived restorativeness (n = 16), and mood (n = 13) were the predominant mental health outcome examined by various physiological and psychological tools. Synthesizing across studies found that brief BGS exposure consistently reduced stress, enhanced mood, and promoted psychological restoration. However, among BGS types and features, more natural settings (e.g., forests, lakesides) outperformed manicured, hardscaped environments, and natural features such as naturalness, plant cover, species richness, and water bodies often amplified benefits.

Conclusion

This scoping review maps an expanding but methodologically heterogeneous experimental evidence base. Most studies included in our review found that even brief exposure to BGSs, especially those more natural, biodiverse, and water-rich environments, can enhance mental health. Designing and preserving biodiverse, nature-rich, high-quality BGSs is critical for promoting public mental health in rapidly urbanizing contexts. Future experiments should address the paucity of studies on blue spaces, examine multi-sensory effects and the effects of virtual nature, and expand to diverse populations with larger sample sizes.