From space to street: A systematic review of the associations between visible greenery and bluespace in street view imagery and mental health

A large body of literature shows that living near greenery supports healthy lifestyles and improves mental health. Much of this research has used greenery measured from a bird's eye perspective. Street view images (SVI) are an important alternative data source that could assess visible greenery experienced by residents in daily life. The current review is the first to systematically critique and synthesize the evidence relating to greenery and blue- space in SVI and its associations with mental health outcomes. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines to conduct this review. First, we identified relevant articles published as of April 2023 in PubMed, Web of Science, Scopus, and CINAHL. Articles meeting inclusion criteria were narratively synthesized. Quality assessments were conducted with the Newcastle-Ottawa Scale (NOS). Based on our search, we identified 35 articles on greenery and bluespace measured with SVI and mental health outcomes. Two-thirds of the included papers found positive associations between greenery in SVI and mental health. The average score for risk of bias was good. Association between visible greenery in SVI and all 10 of the mental health outcomes studied were low or very low quality of evidence and showed limited or inadequate strength of evidence. SVI is likely to be an increasingly used and a validated instrument for estimating health-promoting exposure to greenery. Future research would benefit from the standardization of SVI datasets and computational processes, and studies conducted outside of China and high-income countries. Such advancements would improve the generalizability and robustness of associations between visible greenery and mental health outcomes.