Nature exposure and mental health during the COVID-19 pandemic: A Navigation Guide systematic review with meta-analysis☆

Prior reviews have highlighted that nature exposure was a valuable coping strategy enhancing mental health during the COVID-19 pandemic. However, no existing reviews have determined the quality of evidence and risk of bias of the empirical studies supporting this claim. To address this gap, we employed a Navigation Guide systematic review and meta-analysis approach to investigate associations between nature exposure and mental health during the pandemic. Searches in PubMed, Web of Science, Scopus, CINAHL, and PsycInfo retrieved relevant articles published between January 1, 2020, and March 4, 2024. We used the Navigation Guide methodology to assess the risk of bias and Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) assessments to evaluate the overall quality of evidence. Our search retrieved 113 studies that met the inclusion criteria and reported diverse types of exposure, including nature availability, nature visit frequency, green space accessibility, and green space type, alongside associations with 12 mental health outcomes. Meta-analyses found access to gardens was associated with lower odds of depression [(Pooled odds ratio [OR] = 0.71, 95%CI = 0.61, 0.82), I2 = 0%, n = 3] and anxiety [(Pooled OR = 0.73, 95%CI = 0.63, 0.84), I2 = 0%, n = 3]. Increased time in green spaces was associated with lower level of stress [(Pooled Corr =-0.11, 95% CI =-0.17,-0.05), I2 = 0%, n = 2]. Higher frequency of visits to nature was associated with improved mental well-being [(Pooled standardized beta = 0.10, 95%CI = 0.07, 0.14), I2 = 0%, n = 2] and general mental health [(Pooled standardized beta = 0.11, 95%CI = 0.03-0.38), I2 = 82%, n = 2]. However, the number of pooled studies was small and the overall quality of evidence was "very low" for all outcomes, and high levels of bias were observed (26% of studies had high, 71% probably high). Nonetheless, given the trends in the results, nature-based solutions emphasizing exposure to gardens and green spaces near the home may have promoted psychological resilience during this public health crisis.