Review article
Exploring uncharted territory: Do urban greenspaces support mental health in low- and middle-income countries?

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Abstract

Exposure to urban greenspaces promotes an array of mental health benefits. Understanding these benefits is of paramount importance, particularly in low- and middle-income countries (LMICs), where cities are expanding at an unprecedented rate. However, the existing evidence-base for the health benefits of greenspaces has a strong bias towards high-income countries. Here we systematically assess the emerging evidence regarding the mental health benefits provided by urban greenspaces in LMICs. We carried out a scoping review to assess the extent, type and quality of evidence investigating the relationship between greenspaces and mental health in LMICs. We systematically searched the literature databases Web of Science, Medline, Embase and CAB Abstracts using key terms related to greenspaces and mental health in LMICs. We analysed the resulting studies using a narrative synthesis approach, taking into account study quality, to assess the overall effects on mental health. 36 studies met the inclusion criteria and were included in the narrative synthesis. Studies were heterogeneous in design, study population, greenspace and mental health assessment. While more than 90% of LMICs remain unstudied, we found that eight out of ten studies using validated mental health screening tools detected positive associations between greenspaces and one or more mental health outcomes. These studies mostly took place in upper-middle-income countries. However, there still is a lack of evidence from regions with the highest levels of urbanisation, and only four studies assessed lower-middle and low-income countries. Furthermore, the analysis of mediating and moderating factors indicates that the relationship between greenspaces and mental health in LMICs is context dependent and needs to be assessed in relation to locally relevant environmental and cultural settings. Based on the evidence reviewed here, exposure to urban greenspaces can support multiple mental health outcomes in upper-middle-income countries. However, we still know little about poorer, rapidly urbanising countries. Our findings highlight the need for high-quality, context specific research in those urban areas with the highest levels of urbanisation, and the need to address specific challenges regarding mediating and moderating factors. Future studies should combine robust ecological assessments of greenspaces with validated mental health screening tools.

Introduction

Cities in low- and middle-income countries (LMICs) are expanding at an unprecedented rate (Angel et al., 2011). Urban growth in these regions is placing tremendous pressure on the ability of cities to provide good living conditions for their residents (McPhearson et al., 2016). Not least because through urbanisation, people are less likely to have contact with natural environments such as greenspaces (Soga and Gaston, 2016), potentially with profound implications for mental health (Hartig et al., 2014).

Although urban living can convey many benefits such as providing better access to health care, employment and education (Dye, 2008), living in cities can be detrimental to mental health outcomes, attributable to individual, social and environmental factors (Gruebner et al., 2017). This is particularly true in LMICs, where rapid and unplanned urban growth often results in the expansion of informal settlements and slums (United Nations, 2014), which therefore house a large proportion of the population (McHale et al., 2013). Such settlements tend to be characterised by a lack of security of tenure, inadequate access to basic services and city infrastructure (United Nations, 2015). Informal settlements and slums are often situated in geographically and environmentally hazardous areas, and their residents are affected by poorer physical (Ezeh et al., 2017) and mental health (Subbaraman et al., 2014).

Indeed, mental illnesses affect more than one billion people globally (Rehm and Shield, 2019). Therefore, as cities increasingly shape the context in which people live, it is crucial to better understand the determinants of mental health of urban populations (Galea and Vlahov, 2005). Mental health is affected by a variety of factors including social, economic, psychological, physiological, behavioural, genetic, cultural and environmental factors (Meyer-Lindenberg, 2014). Indeed, interest in the role the natural environmental context in which people live plays for mental health has been growing (Markevych et al., 2017). Exposure to urban greenspaces promotes an array of mental health benefits (Lovell and Maxwell, 2018). Neighbourhood greenness is broadly associated with good mental health in adults (Gascon et al., 2015), reduced prevalence of depression (Roberts et al., 2019), improved social cohesion (Jennings and Bamkole, 2019) and improved measures of mental well-being such as quality of life (Stigsdotter et al., 2010) and life satisfaction (White et al., 2013). Greenspaces are linked to these mental health benefits through different pathways, which emphasise three general functions of greenspace: reducing harm (e.g. reducing air and noise pollution), restoring capacities (e.g. attention restoration and stress recovery) and building capacities (e.g. encouraging physical activity and facilitating social cohesion) (Markevych et al., 2017). While a substantial amount of research investigates the impact of greenspaces on mental health, little is known about the contribution that different qualities of the environment, such as different types of greenspaces or biodiversity, have on mental health (Marselle et al., 2018). Determining which aspects of biodiversity are relevant to mental health is a key research frontier (Bratman et al., 2019).

Although increasingly compelling, the existing evidence has a strong bias towards temperate, high-income settings (Clark et al., 2014; Keniger et al., 2013; Pett et al., 2016). However, it cannot be assumed that findings from HICs are automatically transferrable, given the vast differences in urban conditions, environmental and cultural factors (Markevych et al., 2017). Indeed, current research largely excludes the types of urban environments in which the majority of the world's population live. This bias could be problematic as urban conditions in LMICs often differ from those in HICs for a number of reasons (United Nations, 2015). First, different factors might mediate and moderate the relationship between greenspaces and mental health, through different pathways (Markevych et al., 2017). The mental health benefits people derive from greenspaces may depend on the particular environmental context of a region, such as local climatic conditions (Botzat et al., 2016). Thus far studies have concentrated on a narrow range of temperate regions (Keniger et al., 2013).

Secondly, a society's relationship with the natural environment arises from, and reflects, its cultural norms (Selin, 2003). For instance, people in Turkey use urban parks generally for passive recreational activities such as resting and relaxing, whereas in most high-income countries, urban parks are predominantly used for physical activity (Özgüner, 2011). Hence, cultural norms will be important in underpinning how people interact with greenspaces (Li, 2014), with repercussions for mental health outcomes (Amano et al., 2018). Moreover, perceptions of health and illness, and the clinical expression of major mental disorders varies geographically and across cultures (Gopalkrishnan, 2018; Viswanath and Chaturvedi, 2012). In Nepal, for instance, there is no word for depression (Kohrt and Harper, 2008). It follows that the mechanisms and pathways by which greenspaces affect mental health are likely to vary between cultures (Hartig et al., 2014). Thus, the United Nations' Sustainable Development Goal 11 target 7, which aims to provide universal access to safe and accessible urban greenspaces by 2030 (United Nations, 2019), may be based on findings that are almost solely derived from, and therefore biased towards, conditions in HICs.

Although these biases have been long-standing (Markevych et al., 2017), thus far there has been no synthesis of the emerging body of literature on the mental health benefits people derive from greenspaces in cities in LMICs. There are a number of reviews focusing on the relationships between human health and greenspaces (Dzhambov and Dimitrova, 2014; Gascon et al, 2015, 2016; Hartig et al., 2014; James et al., 2015; Lachowycz and Jones, 2011; Lovell et al., 2014; Shuvo et al., 2020; Tzoulas et al., 2007) and more specifically on greenspaces and mental health (Bowler et al., 2010; Callaghan et al., 2020; Coon et al., 2011; Dadvand et al., 2015; Wendelboe-Nelson et al., 2019). However, to date no review exists which comprehensively assesses the relationship of urban greenspaces and mental health in LMICs. Here we systematically assess the published evidence for the mental health benefits greenspaces may provide to urban residents under different geographical, environmental and cultural conditions in LMICs. At this critical time of development of the field, the aim of our study is to assess the strengths and weaknesses of the available evidence regarding the mental health benefits provided by urban greenspaces in such regions, and to point out ways forward for future research. In particular, we address the following key questions: (1) Do greenspaces promote good mental health of urban residents in LMICs; (2) What are the geographic characteristics of the evidence from LMICs; (3) which environmental and cultural factors mediate and moderate how greenspaces and mental health are associated in LMICs; (4) how were greenspaces assessed and which mental health outcomes were studied in LMICs?

Section snippets

Methods

We carried out a scoping review to assess the extent, type and quality of evidence contained in the heterogeneous body of literature investigating the impact of greenspaces on mental health in LMICs. Scoping reviews are a type of knowledge synthesis. They follow a systematic approach to map evidence and examine the extent, range and nature of the evidence on a topic. Given the heterogeneity of the evidence and the breadth of the research questions, scoping review was the most appropriate

Results

The electronic database search yielded 1801 hits. Removal of duplicates, screening of title and abstract reduced this number to 105 references. Studies excluded at this stage did not meet the inclusion criteria, were not written in English or did not report primary research. Full-text screening further reduced the number of studies to 62 (Supplementary material section 3.3). One study (Gruebner et al., 2011) was excluded because it reported the same data as a related study (Gruebner et al., 2012

Discussion

This scoping review provides novel insights into the relationship between greenspaces and mental health in LMICs. While a large majority of LMICs remain unexplored, we found that eight out of ten studies using validated mental health screening tools detected positive associations between greenspaces and one or more mental health outcomes. The findings suggest that greenspaces can generally support mental health in LMICs.

Regarding positive dimensions of mental health, the evidence indicates that

Conclusions

Urbanisation during the coming decades may have profound implications for the mental health of urban populations in LMICs. The evidence indicates that greenspaces have the potential to improve the mental health of urban populations in these areas. These benefits, however, may depend on the particular environmental and cultural conditions in a given area. Our findings highlight the need for high-quality, context specific research in those urban areas with the highest levels of urbanisation, and

Author contributions

Maximilian Nawrath: Conceptualisation, Methodology, Formal analysis, Investigation, Data curation, Visualisation, Writing – original draft, Review & Editing Solène Guenat: Investigation, Data curation, Review & Editing Helen Elsey: Conceptualisation, Methodology, Writing – review & editing Martin Dallimer: Conceptualisation, Methodology, Writing – Review & editing.

Funding

This work was supported by NERC through the SPHERES DTP (grant number NE/L002574/1)

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

We thank Natalie King for useful discussions that helped to develop the protocol. We are also grateful for the valuable comments from the anonymous reviewers on earlier versions of the manuscript.

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