Associations between Green/Blue Spaces and Mental Health

Living near, recreating in, and feeling psychologically connected to, the natural world are all associated with better mental health, but many exposure-related questions remain.

Using data from an 18-country survey (n= 16,307) we explored associations between multiple measures of mental health (positive well-being, mental distress, depression/anxiety medication use) and: (a) exposures (residential/recreational visits) to different natural settings (green/inland-blue/coastal blue spaces); and (b) nature connectedness, across season and country. People who lived in greener/coastal neighbourhoods reported higher positive well-being, but this association largely disappeared when recreational visits were controlled for.

Frequency of recreational visits to green, inland-blue, and coastal-blue spaces were all positively associated with positive well-being and negatively associated with mental distress. Associations with green space visits were relatively consistent across seasons and countries but associations with blue space visits showed greater heterogeneity.

Nature connectedness was also positively associated with positive well-being and negatively associated with mental distress and was, along with green space visits, associated with a lower likelihood of using medication for depression.

By contrast inland-blue space visits were associated with a greater likelihood of using anxiety medication. Results highlight the benefits of multi-exposure, multi-response, multi-country studies in exploring complexity in nature-health associations.

Poor mental health is the leading cause of disease burden in high-income countries. This may, at least in part, be a consequence of rapid urbanisation and a growing disconnection from the natural world.

A growing body of research suggests that living near and/or maintaining regular contact with nature is beneficial for a range of health and well-being outcomes, but several issues remain outstanding.

First, there is a lack of clarity about the relative importance of merely living near nature, variously referred to as residential proximity, neighbourhood exposure or indirect contact, compared to more direct interactions including deliberate engagement through recreational visits. Although some benefits to mental health and well-being may result from mere neighbourhood exposure, e.g. reduced noise and air pollution and lower temperatures, others are thought to derive from voluntarily spending time in natural settings for relaxation, meeting others, and/or undertaking physical exercise. To date, the vast majority of studies have focused on residential proximity and although a positive association is sometimes reported with recreational visits, there is also evidence that many people rarely visit local nature, while others travel, sometimes quite far, outside of their neighbourhood for exercise and nature-based recreation. Proximity is a far from perfect proxy for use.

Second, emerging evidence suggests that mental health may be non-linearly related to recreational exposure, with diminishing marginal returns beyond a certain threshold. As with many other ‘goods’, it may be that the benefits of nature-based recreation become less pronounced with each additional visit. Greater clarity about the relative importance of residential exposure and recreational visits, as well as their potentially non-linear relationships, is critical in designing public health interventions that not only improve availability but also support the most appropriate levels of use, both locally and further afield.

Third, most research has operationalised nature in terms of ‘green space’ (e.g. parks, woodlands, street trees, vegetation cover) and under-explored the potential role of both inland-blue spaces (e.g. rivers, lakes), and coastal-blue spaces (e.g. beaches, promenades), for mental health. Although green and blue spaces share many qualities (e.g. cooling effects, biodiversity), blue spaces also offer alternative recreational activities (e.g. swimming) and have additional features (e.g. unique soundscapes). It is only through examining both in tandem that we will get a clearer idea of their relative potential benefits for mental health.

Fourth, the field has used a wide range of mental health metrics, including indices of both positive and negative mental health. Rates of poor mental health tend to be lower among populations living in greener neighbourhoods, and one-of nature walks have been shown to reduce symptoms of anxiety/depression in at-risk populations. However, there has been relatively little large-scale research exploring relationships between voluntary, recreational time in nature and indicators of mental health. Tis is important because meta-analyses suggest that the benefits of direct nature exposure tend to have a larger effect on promoting positive emotions than reducing negative ones, and thus it may be that indicators of positive mental health are more sensitive to recreational visits than negative ones. Again, this is best explored in studies that include multiple exposure metrics alongside multiple mental health outcomes.

Fifth, research suggests that psychological connectedness to the natural world, e.g. feeling part of nature or seeing beauty in natural things, is also positively associated with positive well-being. Given that people high in nature connectedness also tend to report more recreational visits, any positive association between visits and well-being may be due to the underlying nature connectedness an individual has, rather than a product of the environment itself.

To unpack this possibility, more research is needed to explore the simultaneous relationships between exposures, nature connectedness and mental health, so that their unique roles can be identified.

Finally, there may be important seasonal and societal/cultural differences in the way nature affects mental health. For instance, most research using the Normalized Differential Vegetation Index (NDVI) as its measure of residential green space uses summer data, and applies it to health data for the whole year even though relationships may be different when leaf cover is lower in winter months. Similarly, blue spaces may be better for mental health in summer/autumn when the water temperatures are higher. Living near and spending time in green and blue space is also likely to be quite different, for instance, in southern European countries than northern European countries. Not only are temperatures and vegetation different, hours of daylight vary substantially across the year potentially affecting time outdoors.

Results

Nature connectedness was positively associated with positive well-being, negatively associated with mental distress, and negatively associated with depression medication use.

The frequency of visits to green spaces was positively associated with positive well-being and negatively associated with mental distress and the use of doctor-prescribed depression (though not anxiety) medication. Extending previous research, those who made more frequent visits to both inland- and coastal- blue spaces also reported more positive well-being and lower rates of mental distress, even controlling for the number of green space visits.

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