According to the study, greenery plays an effective role in improving mental health by reducing noise pollution and increasing air pollution. Jeenah Moon/Reuters

With the ever-growing population and rapid industrialisation of urban areas around the world, living in prosperous cities and towns in the 21st century can be a considerably strenuous experience. The intensity of this pandemonium is only exacerbated by equally stressful factors such as overcrowding, traffic, increased crime rates, poor housing facilities, busy commutes, unreliable transport networks and the palpable pressure from those people who are always in a rush.

When bearing this in mind, it should come as no surprise that the overwhelming lifestyle of these cities is also associated with issues in mental health, particularly stress and anxiety.

However, a recent study published in the Environmental Research Journal reassesses that the key to reducing feelings of stress and anxiety could lie in the green spaces dotted around urban areas.

Greenery, in general, is a vital and natural resource with its ability to detoxify the air and promote emotional well-being. Because of these natural benefits, people will frequently visit undeveloped green spaces (i.e. public parks, fields, botanical gardens) in order to exercise, meditate, socialise, relax, take in the scenery, or just simply sit with a coffee and clear their head. And the added beauty of green spaces is that they are open to the public and usually free too.

Previous studies into this link between green spaces and improved emotional well-being have discovered how noise pollution increases the risk of nerve damage and cardiovascular disease, with these conditions all being linked to anxiety and depression. However, the presence of green spaces can decrease noise pollution and relieve air pollution, thus reducing oxidative stress.

work-related stress
Depression and anxiety are two of the most common mood disorders and usually coexist with intense feelings of stress. REUTERS/LukeMacGregor

To conduct their study, the researchers used eighteen relevant observational studies to integrate the findings, interpreting them in terms of the difference in perceived mood levels per 0.1 unit increase in the normalised difference vegetation index (NDVI) and 10 per cent increase in the percentage of green spaces.

Ultimately, the findings revealed that an increase in green space proportion by 10 per cent was associated with a four per cent reduction in the risk of depression, with only a slight effect on anxiety. Each 0.1 unit increase in NDVI was associated with a seven per cent reduction in the risk of depression in smaller studies.

The meta-analyses of these eighteen studies showed much stronger associations with mental health in smaller samples, particularly with younger individuals, with a clinical diagnosis of anxiety or depression, compares to those who were diagnosed with scales. The researchers even systematically analysed the relationship between green spaces in schoolyards and adolescents' mental health, although the lack of quantitative analysis made it difficult to ascertain the qualities and metrics of green space that were best for their mental health.

The results of another meta-analysis revealed a significantly positive impact on mental health when the subjects were gardening, planting or engaging in other activities surrounding horticultural therapy, which is also well-known to decrease stress and promote peace within the mind.

When examining the results, the researchers concluded that improved green space exposure may indeed assist with the prevention of anxiety and depression. They wrote: "Higher green space exposure might be helpful for depression and anxiety disorders. Therefore, improving or preserving green space should be regarded as a promising intervention for public health."