Exposure to nature brings a wide range of health benefits to humankind [1
]. Population-level studies in developed countries have shown that people living in areas with higher levels of nature have improved mental [3
], physical [4
] and social [6
] health, are more likely to undertake physical activity [7
] and have a greater connection with nature [9
]. Critically, these health benefits do not occur independently, but are delivered concomitantly as people spend time in nature. Research on determining the causal pathways by which these benefits are delivered is now increasingly well developed [11
For most people, the nature around their home will provide their most common nature interactions [14
], so it is likely critical for the provision of health benefits. This “nearby nature” offers an immediate and easily accessible opportunity for people to experience nature [15
]. Such nature is provided by a combination of public and private green spaces. People will experience nearby nature as they consciously spend time in it, for example through gardening, and as they are subconsciously exposed to it as a by-product of other activities, such as walking to shops [1
]. Private gardens are a major component of urban green space and contribute disproportionately towards nearby nature [17
]. A significant number of private green spaces in the UK contain tall trees and vegetation [19
] and are thus inevitably a central focus of people’s nearby nature experiences [20
]. Gardens also provide locations where people can experience other multi-sensory components of nature that can be beneficial for health, such as sunlight and fresh air.
Given the wide availability of nearby nature, there is a huge opportunity to capitalise on it for health outcomes. Vegetation in the environment is associated with enhanced mental well-being [21
], and short durations of exposure to natural environments deliver an immediate reduction in blood pressure [24
] and greater feelings of mental restoration [25
]. However, there is currently a dearth of information to guide recommendations on what kinds of nature and how frequently and how long people should spend in nature for improved health.
The nature dose-response framework [13
] distinguishes three components of nature exposure, namely its intensity (quality and quantity), frequency and duration [13
]. A dose-response approach can be used to develop minimum and optimal-dose recommendations to nature similar to those for physical activity [29
]. Indeed, deconstructing nature dose is critical to identifying what environmental management interventions might be required to enhance the benefits that people receive from nature or precisely how people should alter their behaviour [13
Here, we survey 1023 respondents in Southern England, UK, to quantify the link between five health outcomes and three measures of nearby nature dose. These five health domains all had plausible mechanistic pathways linking nature with health: mental health (self-reported depression) [21
], physical health (self-assessment of general health) [24
], social health (perceptions of social cohesion) [6
], positive physical behaviour (level of physical activity) [30
] and nature orientation (nature relatedness scale) [31
]. Measures of nature dose were time spent in the garden in the previous week (frequency and duration of nature dose) and the quantity of vegetation surrounding the home (as a measure of dose intensity). Nature around the home commonly varies according to a suite of socio-demographic factors that also affect health (Table S1
). Thus, we adjust for socio-economic and lifestyle covariates in our analyses to improve the detection of the nature benefits distinct from other potential confounding factors. We then use dose-response modelling to estimate the point at which the frequency and duration of visits to private green spaces and the quantity (intensity) of vegetation around the home altered the health outcomes measured here that could be represented in a binary fashion (depression).
The survey respondents tended to be younger, but otherwise were of a similar demographic to those in the local population (Table S2
). Across the respondents’ neighbourhoods, there was an average vegetation cover of 24% (±9.1% SD) and built cover of 55.7% (±14.2% SD), with most respondents having access to private gardens (91.4%). We found that four of the health outcomes, namely depression, perceptions of social cohesions, levels of physical activity and nature orientation, improved with an increasing frequency and duration of exposure to nearby nature (i.e., there was a positive association with perceptions of social cohesion, levels of physical activity and nature orientation and a negative association with levels of depression; Table 1
; Figure 1
). We also found that a greater intensity of nature exposure was associated with lower levels of mild or worse depression and higher levels of nature relatedness (Table 1
; Figure 1
). These relationships held even after accounting for potential covariates. We did not find any relationship between nearby nature and self-reported physical health (Table 1
; Figure 1
). Respondents who spent relatively less time out of doors in the survey week were more likely to have depression and to have worse physical behaviour, while respondents who spent relatively more time outdoors had increased nature relatedness.
The odds of having mild or worse depression were lower than the null model when the frequency of garden visits was once a week or greater, with further incremental gains until an optimum of 4−5 times a week after which subsequent benefits to mental health were limited (Table 2
; Figure 2
a). There was a minimum and optimum threshold at five or more hours in the duration of the total time spent in the garden, after which the levels of depression rapidly decreased (Table 2
; Figure 2
b). The dose-response relationship was less consistent for nature intensity. The levels of depression were lower in people who lived in neighbourhoods with 15% vegetation cover followed by no effect at 20% cover, then further incremental gains in lower rates of depression at 25%, until 35% vegetation cover was met (Table 2
; Figure 2
c). The optimal dose-intensity did not appear to have been met in this study (Figure 2
We demonstrate that nature close to the home is associated with quantifiable benefits to population health. We found measurably better mental health, social health, positive physical behaviour and nature orientation with greater frequency and duration of time spent in nearby nature. We also showed lower levels of depression and greater nature orientation in people who live in greener neighbourhoods. However, we found no relationship with self-reported physical health.
We carried out a dose-response analysis to identify the point at which exposure to nature was associated with a lower incidence of depression in the surveyed population. The key challenge for the cross-sectional design used in this study is the potential existence of a circular feedback loop, where people with depression might avoid going outdoors. Thus, a lower dose of nature might be an outcome, rather than a cause of the observed depression. However, this type of dose-response analysis should not be considered in isolation; rather, it adds a thread of evidence to the growing body of literature demonstrating a link between mental health outcomes and nature dose (as per Hill’s criteria for causality; [57
]). As such, if the link is in fact casual, our dose-response analysis suggests that up to 5% and 27% of depression cases within our survey population could be prevented if all city residents spent 10 min or more a week in their garden or five hours or more in total, respectively; or, if neighbourhood vegetation is managed to a minimal level of 15% cover, it could prevent up to a further 5% of depression cases. If scaled-up to the urban population, this suggests that behavioural interventions that encourage exposure to nearby nature and even minimum recommended levels of neighbourhood greening could have considerable impact on population health. The potential savings associated with improving nature exposure would be significant given that in 2007, it was estimated that depression cost the English economy £7.5 billion in health costs and lost workdays [58
We found that across four self-reported health outcomes, the frequency of nature exposure was a stronger predictor than the duration of exposure. This has implications for the design of health interventions. It has been recognised in the sport sciences that short frequent exposures are a time-efficient strategy to induce health outcomes [59
]. Thus, people may be able to gain their necessary nature dose while going about their daily activities, such as walking to shops, or spending time in a room with a view of nature.
The dose-response analysis showed that all three types of exposure to nearby nature had positive associations with survey population levels of depression. The dose-response relationship observed for frequency (≥1 garden visit a week) and intensity (≥25% vegetation cover) is considered to provide some evidence of causality according to Hill’s criterion (i.e., reduced levels of depression with increasing increments of dose) [57
]. Visiting gardens 4−5 times a week appeared to create an optimal response and was associated with 17% lower levels of depression in the survey population; further increases in dose had limited further benefits. An optimal dose had yet to be reached for intensity, because few respondents lived in neighbourhoods with >35% tree cover, and so, the standard error was too great to detect a reliable signal. A higher duration of exposure was also associated with lower levels of depression, with a minimum and optimum threshold of significantly lower levels of depression beyond five hours of exposure. There is evidence that experiencing nature improves mood in people with depression [34
], and multiple and multi-sensory elements doubtless contribute to these improvements through a variety of mechanistic pathways. Respondents who spent relatively less time out of doors in the survey week were more likely to report worse depression. Intriguingly, this suggests that relative nature experience may be a contributing factor. The type of nature exposure and the severity of depression may have important implications for the mechanistic pathway through which nature affects mental health, and thus, nature dose recommendations could be tailored for the specific needs of people with poor mental health.
Population-level studies have shown that increased green space has been associated with lower mortality from cardio-vascular disease [4
] and enhanced general and self-reported health [60
]. However, other studies found no association between green space cover and mortality, or even increases in mortality at the citywide scale [62
]. This study further suggests that physical health benefits may be location specific depending on risk factors prevalent in individual cities.
We quantified the relationship between spending time in nearby nature and social health, showing that visiting the garden just once a week or spending up to even 30 min a week in the garden is associated with significantly greater perceptions of social cohesion between neighbours. Green space provides opportunities for more frequent encounters between neighbours that create and strengthen social ties, leading to increased social cohesion [64
]. Subjective experiences of the views of nature from home, the quality of nature and the amount of time spent in nature have all been linked to perceiving one’s community as linked and cohesive [41
], illustrating that nearby nature provides a variety of benefits to community health through multiple pathways.
The frequency and duration of time spent in nearby nature were important predictors of physical activity. Although we did not assess the type of physical activity, the strong relationship does suggest that either spending time in nearby nature is a strong motivator for people to engage in physical activity or that more active people spend more time in nearby nature (reviewed by [66
]). Either way, these green spaces not only provide important locations to exercise, but there is robust evidence that they also enhance the benefits of physical activity to both physical [66
] and mental health [25
], which may further motivate people to exercise more.
For the first time, we have quantified the relationships between doses of nature close to the home and nature orientation. Our analysis shows that once a minimal dose threshold is met, there are consistently higher levels of nature orientation with further incremental increases in dose. Our results support previous research that showed a positive relationship between time spent in the garden with nature orientation [9
]. Interestingly, people who spent relatively more time out of doors had higher nature relatedness, suggesting that the recent doses of nature may contribute towards shaping nature orientation. Maintaining nature around the home may therefore be critical for both health and biological conservation, because nature orientation has been associated with improved life happiness [46
], reduced anxiety [45
] and environmental behaviour [67
This study used a cross-sectional design, which inevitably has both advantages and limitations. The main advantage is that this allows the simultaneous analysis of multiple risk factors. The limitation is that this design cannot definitively establish a cause-effect relationship; however, these pathways are becoming increasingly well developed by other studies [11
]. This study also relied on self-reported data, which may lead to common method bias. Thus, additional studies using more objective health indicators, including hair cortisol or heart rates, might be needed. Health is a complex issue with multiple drivers, and although we controlled for key socio-economic covariates known to influence health, the impact of life events, such as family emergencies, is difficult to control for. The low R2
(see Table 1
) indicates a low predictive power; however, within the variables tested, exposure to green space was a significant predictor of improved health. This study was conducted over a two-week period in May when the benefits of nature are predicted to be greatest and the levels of depression may be lower [68
]. Nonetheless, experiences of nature vary greatly across the year, and understanding how this variation influences nature doses and the associated health benefits is an important direction for future research. Further, studies unpicking the influence of nature exposure on health relative to factors associated with time out of doors, such as exposure to sunlight and vitamin D absorption, are required. Finally, the benefits of contact with nature vary across socio-economic groups, cultures and environments, and as such, caution must be applied when drawing conclusions applicable to broader populations. Future research needs to establish how the health benefits from nature vary across these different axes.