The second in a series of posts on natural capital and mental health, guest blogger Dr Lindsay Walker explores the emerging evidence of the impacts ‘green care’ or ‘ecotherapy’ can have on depression.

In the UK, one in four people will experience a mental health problem in any given year, and evidence suggests that there is a substantial gap in mental health treatment opportunities across the country, with around 75% of people living with mental health issues receiving no treatment.

As the reporting of mental health disorders is increasing, along with the associated costs and demand for health and social care services, there is greater need for evidence-based health interventions that are both cost effective at improving health outcomes as well as being accessible to the general population.

There is growing evidence that highlights that the natural environment can be used as a resource for both the treatment and prevention of mental health problems. These nature interventions, also known as ‘green care’ or ‘ecotherapy’, have been found to positively affect mental health related outcomes, including depression.

For example, a recent review of the benefits gained through participating in conservation activities highlighted that exposure to natural environments was one of the important pathways to positive mental health outcomes.

Additionally, an independent evaluation by researchers from the University of Essex on the impact of the ecotherapy programme “Ecominds”, run by the mental health charity Mind, found that 71% of participants displayed reduced depression scores after taking a walk in nature. Of the control group who walked through a shopping centre, 45% of participants displayed reduced depression scores, with 22% reporting increased feelings of depression. Furthermore, through working with the New Economics Foundation, it was calculated that participating in Ecominds produced a £7,082 saving per individual through reduced NHS costs, welfare benefit reductions and increased tax contributions (the latter two due to the success of the programme with helping people move back into employment or training).

This economic saving is not to be sniffed at – in the UK 70 million sick days were taken due to mental health problems (in 2007), costing an estimated £70-100 billion per year. Globally, costs due to mental health problems were estimated at £1.6 trillion (US$ 2.5 trillion) in 2010, with a projected increase to £3.8 trillion (US$ 6.0 trillion) by 2030. This is the largest single source of world economic burden.

The natural environment has been shown to have a protective effect on self-reported mental health. For example, analysing longitudinal data has shown that people living in urban areas with more greenspace report lower mental health distress and higher wellbeing compared to when living in urban areas with less greenspace. Furthermore, using the same longitudinal data, it was found that moving to a greener urban area resulted in sustained mental health improvements (though the reverse was not found). For older people, living in environments with more greenspace has also been associated with reduced likelihood of depression. These restorative effects associated with living near green spaces were not due to increased physical activity in neighbourhoods with increased availability of green space. Rather, the mental health benefits gained from living near green spaces were largely independent of whether people went for walks or not. Additionally, there is a small but growing sample of studies investigating the impact of the type and quality of natural environments on mental health. It has been found that higher densities of greenspace type (e.g. “broadleaf woodland”) are associated with a higher prevalence of good health, and there is suggestive (but inconclusive) evidence that biodiverse natural environments may promote better health.

Several studies have shown that there is a socioeconomic inequality with common mental health problems such as depression, with the more disadvantaged sections of society disproportionally affected by such health issues. However, having access to green spaces significantly reduces the gap with socioeconomic inequality in mental wellbeing, highlighting that the natural environment could play a part in reducing inequalities in health.

The underlying mechanisms regulating the positive impact of nature interventions on mental health disorders are likely multifarious and are not currently well understood, although studies are now beginning to address this gap in knowledge. Researchers from Stanford University monitored the activity of a region in the brain linked to a key factor in depression in participants before and after walking in either a large park or a high-traffic street. Those who had walked in a natural area displayed decreased activity in this region of the brain as well as corresponding lower levels of self-reported depressive symptoms. In Japan, researchers found that people who walked in the forest, rather than around city centres, had reduced stress levels, lower blood pressure and lower pulse rate, indicating that people experience a more relaxed state while in the forest.

Currently more than 50% of people live in urban areas, with the global urban population projected to be over 75% by 2030. This urbanisation, although associated with many benefits, is also linked to increased levels of mental health issues. Given the increasing evidence of the mental health benefits of both interacting with and being near nature, greening of urban areas could be considered as a population health intervention. This could have substantial implications for future national and local policy, with accessibility of good quality green spaces better integrated into planning regulations.