The science is relatively nascent, the sample sizes are small, and questions remain about the potential tangling of causation and correlation, but the consistency of findings across a variety of places, groupings, approaches and settings is uncanny. A study of mailroom workers found that those workers who had some daily exposure to sunlight were significantly more productive (by up to 16 per cent). An assessment of students found those who lived in dorms with green views had better cognitive function than those who didn’t. A study of inmates at the State Prison of Southern Michigan showed that those (50 per cent of them) whose cells looked onto trees were 24 per cent less likely to become physically or mentally ill than those who gazed only at brick walls.
Hospital patients who had a view of trees and bushes also did better while recovering from surgery than those who had views of walls; they asked for half the amount of painkillers and buzzed the nurses half as often. This study, conducted by Roger Ulrich in 1984, prompted many hospitals to plant ‘healing gardens’.
A Canadian study found that having ten or more trees in a city block ‘improves health perception in a way that is like an increase in annual personal salary of $10,000’. Even better, ‘having eleven more trees in a city block decreased cardiometabolic conditions in ways compared to an increase in an annual personal income of $20,000’. In another study, people leaving an urban park were more likely to help a passerby than those entering it.
As author Florence Williams says simply: ‘The more nature, the better you feel.’
MORE THAN A CENTURY AGO, Florence Nightingale instinctively understood that plants and gardens had therapeutic properties. In her seminal work, Notes on Nursing, written in 1859, she outlined her belief that patients would heal better if they were able to look at beauty, brilliant colours and a variety of objects, or just some kind of view:
I have seen, in fevers (and felt, when I was a fever patient myself) the most acute suffering produced from the patient (in a hut) not being able to see out of window, and the knots in the wood being the only view. I shall never forget the rapture of fever patients over a bunch of bright-coloured flowers. I remember (in my own case) a nosegay of wild flowers being sent me, and from that moment recovery becoming more rapid.
People say the effect is only on the mind. It is no such thing. The effect is on the body too. Little as we know about the way in which we are affected by form, by colour and light, we do know this, that they have an actual physical effect.
We are joined to the Earth in ways we barely understand. In 1984, American biologist E.O. Wilson coined the term ‘biophilia’ for an innate love of the natural world, which he argued is intrinsic to being human. German social psychologist Eric Fromm called it ‘the passionate love of life and all that is alive’. Wilson suggested that this ‘innate emotional affiliation of human beings with other living organisms’ has a genetic basis, and is found in genetic memories, and scientists have been trying to understand and test the idea ever since.
Unsurprisingly, much of the early pioneering research into the ways in which nature can counter the darker sides of urbanisation originated in the world’s largest city, Tokyo, which currently houses 37 million people in its greater metropolitan area. In the 1980s, increasing awareness in Japan of the benefits of dousing yourself with nature gave rise to the practice of forest bathing or shinrin-yoku. Based on ancient Buddhist and Shinto practices, forest bathing is a kind of preventative medicine that involves immersing yourself in nature while engaging all the senses; it has recently spread throughout the Western world.
Dr Qing Li, an environmental immunologist at Tokyo’s Nippon Medical School has led the research into the science, and his book Shinrin-Yoku: The Art and Science of Forest-Bathing invites us to immerse ourselves in nature. In 2010, Li found that the number and activity of immunity-supporting cells rose after a forest visit and stayed elevated for a month; the cells did not respond in any way to carefully crafted similar trips in urban places. Since then, research has also shown that forest bathing has positive benefits on the cardiovascular system, especially in reducing hypertension and coronary artery disease; the respiratory system, including alleviating allergies; and mental health, by reducing depression and anxiety (and even ADHD), enhancing mental relaxation, and increasing feelings of awe, which in turn leads to an increase in gratitude and selflessness. Sitting in his small, uncluttered office in Tokyo, Dr Li told me that people suffering ‘nature deficit disorder’ regularly come to him seeking a cure for a problem they have no name for: a general unease, anxiety or sadness — crucially, a forest walk has been shown to limit, or decrease rumination. His passion is obvious: the science has repeatedly confirmed his gut instinct, and now he is called upon to give lectures around the world on the subject.
Ongoing worldwide research confirms the benefits of bathing in nature. In 2017, a meta-analysis assessed sixty-four studies of forest bathing published between 2007 and 2017. The authors stressed the need for longitudinal research but found strong evidence that time in nature reduces stress, including ‘technostress’. Bathing in nature was found to help Danish soldiers with PTSD; Koreans who have suffered strokes, neckaches or chronic pain; Swedish dementia patients; Chinese hypertension sufferers; Israeli school students with learning difficulties; Japanese diabetics and cancer patients; stressed Florida officer workers; Lithuanians with heart disease; and depressed American retirees.
In one study of Korean patients who had been hospitalised for depression, psychotherapy carried out in a forest had discernably superior results to the same therapy performed in hospital. In another study, severe depression in alcoholics was lightened. The health benefits spanned ages — from childhood obesity (a survey of 7000 children in Indianapolis found a lower incidence of obesity in greener neighbourhoods) to longevity in adults (a Tokyo study of 3000 people over seventy-five found mortality was protected by ‘green, walkable paths and spaces’, irrespective of age, sex, marital or socioeconomic status, or initial health). Nature therapy has also significantly decreased the pulses of anxious middle-aged Japanese women and the blood pressure of middle-aged Japanese men, and made both genders sleep more deeply. Just sitting on a chair and looking at a forest made a group of young male students calmer, according to analysis of their saliva.
The authors of the 2017 meta-analysis wrote:
In general, from a physiological perspective, significant empirical research findings point to a reduction in human heart rate and blood pressure and an increase in relaxation for participants exposed to natural green spaces . . . This indepth review illustrates, honors and supports the increased awareness of the positive health-related effects (e.g., stress reduction and increased holistic well-being) associated with humans spending time in nature, viewing nature scenes via video, being exposed to foliage and flowers indoors and the development of urban green spaces in large metropolitan areas worldwide. Not only valid and reliable psychometrics have been implemented, but valid and reliable physiological measurements have been used to show significant and potentially healing and health promoting effects.
They also concluded that the cardiovascular benefits of forest bathing ‘are apparent regardless of age, gender, socio economic background, or previous exposure to a nature setting’.
There are some significant shortcomings with the research. Many sample sizes are small; most measure only brief, single exposures to nature; and many subjects are young, healthy male students — more randomised, controlled experiments are needed. The impact of physical activity is not often differentiated, although many studies compare the same levels of activity — mostly walking — in city and forested areas. And the effects studied are short term: the longevity of benefits has not been determined. There are still many questions, too, about how to define green space, and exactly what kind and length of exposure to nature is required, and whether you need to be in nature or just focus on it. But the findings about mood improvement are unequivocal, and, as Frances E. ‘Ming’ Kuo of the University of Illinois has pointed out, it is natural to assume, according to the evidence so far, that ‘total exposure is important; all forms and quantities of exposure are helpful; and the greener the better.’ Especially in the sharpest and harshest of urban environments.