HISTORY OF NATURE AND HEALTH
The first recognition and discovery that plants influence human health dates back to 2000 BC. In 500 BC, Mesopotamian and Persian gardens were built and designed specifically to please “all the human senses” (Scott 1147). In the middle ages, Monastic gardens, as seen in Figure 1, were designed as a place for the sick to stay and recuperate. Within the 18th and 19th centuries, hospitals and asylums began to encourage their patients to go to their gardens in hope to get their mind off their current health situation. In 1940, the US veteran hospital had their patients work with plants within the hospital gardens and found that it improved their “emotional, mental, and physical health” (Scott 1147).
(Photo: Château de Castelnaud, Monastic Garden, http://www.pauldorpat.com)
Figure 1: A monastic garden found within France used for food and medicine.
HORTICULTURAL THERAPY
In the 1970s, a new therapy emerged: Horticultural Therapy. Horticultural therapy is therapy which uses plants and gardens to positively effect health. This therapy can include hands on activities such as interacting with nature or gardening as well as passive activities such as looking outside. It wasn’t until the 1980’s though that this therapy was common within the health sciences. Horticultural therapists must be trained in both plant and human sciences as well as much be certified by the American Horticultural Therapy Association (AHTA).
Horticultural Therapy has been found to relax patients, reduce pain perception, increase attention, improve mood, control agitation, create meaningful engagement, enhance social interactions, improve self-esteem, and enhance physical well-being within adults (Scott 1147).
An experiment to compare horticultural therapy and conventional therapy was done in urban Serbia. The urban Serbian population was selected as participants due to their socio-economic crisis, large number of stresses, and years of trauma which has affected the mental health of the Serbian population. Due to these factors, the urban Serbian people have experienced an increase in depression, stress, and psychosomatic disorders. The experimental group was asked to stay in gardens and receive horticulture therapy. While the control group was asked to receive only conventional therapy. The results showed that there was a more positive impact on health in the experimental group than the control group. Additionally, it found that these patients experienced more and complete recuperation from their stress, depression, and anxiety than the control group (Vujcic 2017).
ULRICH STUDY
In 1991, Roger Ulrich conducted a study which looked at the effects of nature on human stress levels. Subjects were placed in variety of stressful situations and were then asked to watch a video depicting either an urban or a natural environment. Before and after the video, researchers collected the subjects’ self-reported stress levels, heart rate, muscle tension, skin conductance, and blood pressure, the results are found within Figure 2. The study found that subjects who viewed natural environments such as trees/plants in a variety of stressful situations experienced a more rapid and complete recovery than those who viewed urban environments. The subjects who viewed natural environments took an average of four minutes to recover from their stressful situation (Wolf 2014).
| Part of the Experiment | Results |
| Viewing a TV playing either a natural or built setting video in a doctor’s office | Subjects who watched the nature video had a lower pulse rate and blood pressure than those who watched an urban video. |
| Viewing art depicting nature or urban settings | Subjects who viewed the art depicting nature settings had lower stress and anger than those viewing art depicting urban settings |
| Viewing trees or an urban setting outside a window | Subjects who saw trees outside the window had lower blood pressure than those who saw a urban setting outside a window |
| Driving simulations with and without vegetation | Subjects that drove with vegetation had a quicker stress recovery and were less likely to feel stress later than those who drove without vegetation. |
| Spending 30 minutes in an urban and natural environment after a stressful situation | Subjects in both environments reduced stress but the natural environment had a greater reduction than the urban environment |
| Listening to nature or urban sounds | Subjects who listened to nature sounds recovered faster from stress than those who listened to urban sounds |
Figure 2: Specific parts and results of Ulrich’s experiments
SHINRIN-YOKU
Shinrin-yoku is a Japanese term which means taking in the forest atmosphere or forest bathing. This term was created by the Japanese Ministry of Agriculture, Forestry, and Fisheries in 1982. An experiment was conducted within Japan to view the effects forests on human health. Twelve different subjects were asked to either walk within one of Japan’s 24 forests or a city setting. Half of the subjects walked within forest areas while the others walked within the city the first day. On the second day, the subjects switched and walked within the other environment. Salivary cortisol, blood pressure, pulse rate, and heart rate were recorded in the subjects before and after each walk. The experiment found that when subjects walked within forest settings, they had lower concentrations of cortisol, lower pulse rate, lower blood pressure, greater parasympathetic nerve activity, and lower sympathetic nerve activity than when walking within an urban setting. Additionally, the experiment found that when walking in nature it enhanced the high frequency component of the heart rate variability and lower low frequency to high frequency ratio within heart rate variability. Finally, the experiment discovered that forest environments lower the hemoglobin concentration within the left prefrontal area of the brain, an indicator of cerebral activity (Park 2009). Park concluded from this experiment that forest atmospheres decrease stress and increase perceived happiness.
GREENSPACES
In 2007, an experiment was performed to look at the effects of greenspaces, shown in Figure 3, on human health. The UK census was used to quantify health within a certain area based on the description of their health as either “good”, “fairly good”, or “not good” over the past year. Additionally, the greenspace within a specific area was quantified based off the Generalized Land Use Database. The experiment also considered the degree of urbanity of the specific area using the Urban-Rural Classification. The experiment has found that typically across all areas, the more greenspace within a specific area the less amount of people who described their health as poor. All urban areas as well as rural low-income areas experienced the greatest positive effects to green spaces (Mitchell 2007).
Within England green spaces, 32.9 million people in England use these green spaces making 2.6 billion visits. Not only are greenspaces beneficial to health but also much more. Greenspaces are socially inclusive and are free and available to anyone. Interactions between people within these spaces can provide a multitude of opportunities such as environmental education and a space for outdoor activities. Not only that but greenspaces provide an area for children to be energetic, imaginative, play, and engage in outdoor nature. Greenspaces also aid in maintaining biodiversity and reducing population within the area. (Swanwick 2003).
(Photo: Della Hansmann, Ping Tom Memorial Park, http://moss-design.com/chicago-parks/)
Figure 3: A greenspace found within Chicago.
LEVELS OF ENGAGEMENT IN NATURE
There are three levels of engagement with nature, according to Pretty, all of which improve mental health. The first level of engagement involves only viewing nature, the second level of engagement involves being in the presence of nature, and the third level of engagement involves interacting with nature. It was found that the third level of engagement had the biggest improvement on mental health (Pretty 2006).
1st level engagement experiments have found …
- People who have a window view at work have fewer illnesses, feel less frustrated, are more patient, and express greater enthusiasm for work
- People claim to be able to think better when their window view is of greenery
- Alzheimer patients with access to a garden were less aggressive and violent
- Prisoners who could view farmland and trees had 24% lower frequency of sickle cell visits than those facing the prison yard
- Post operation patients who could view trees outside their window stayed in the hospital for less tie and needed less medication than those who had a view of buildings outside their window
- People who sit in a room with views of trees have a more rapid blood pressure decline than those sitting in a windowless room (Pretty 2006).
2nd level of engagement experiments has found….
- Children who live in houses with nearby nature have higher levels of cognitive functioning than children that live in houses without nearby nature.
- 54% of children that spent time within the hospital garden felt more relaxed, 24% felt more refreshed, 18% felt more positive, and only 10% felt no affect (Pretty 2006).
3rd level of engagement experiments has found…
- Walking in nature reduces lower blood pressure more than walking in an urban street (Pretty 5)
- “outdoor garden provide access to fresh air and sunshine and exercise, which helps regulate circadian rhythm that regulate sleep and appetite” (Scott 2017)
WEATHER AND MENTAL HEALTH
Seasonal variation in mood has been recorded with seasonal affective disorder, depressive symptoms, bulimia nervosa, anxiety disorders, and other mental health problems which worsen within colder weather and limited sunlight (Berry 2009).
WHY DO WE EXPERIENCE THESE EFFECTS WITH NATURE?
Hamilton discusses two potential theories as to why nature has this “restorative” power on human health: stress reduction theory (SRT) and attention restorative theory (ART).
Stress Reduction Theory
Before industrialization, landscapes which contained water and vegetation were the most beneficial to survival for human. Stress reduction theory believes the positive emotions that we feel when we view these landscapes are evolutionary and innate so that humans had the urge to stay within these types of landscapes. These landscapes effect human cognitive processes without even needing to think about it (Hamilton 2012). According to Jiang 2020, the emotional response to greenspace is immediate, unconscious, and spontaneous, and is accompanied by increased positive feelings and reduced levels of arousal according to this theory.
Attention Restorative Theory
This theory states that people shift their attention to nature when in its presence, which then shifts their attention away from other distractions. According to this theory, there must be four things that landscapes must contain to effectively direct people’s attention away from other distraction as well as have restorative effects. First, the person must feel as though they are immersed in the landscape. Additionally, the person must feel as though they have escaped their daily life stressors. Next, the environment must be fascinating to the person. Finally, the landscape must be compatible to the person (Hamilton 2012).
STRESS
There are a multitude of definitions of stress as well as types. According to Baum 1990, stress is defined as a negative emotional experience accompanied by biochemical, physiological, and behavioral changes directed toward adaption either by manipulating the situation to alter the stressors or by accommodating its effects. Within my experiment, I will have participants record when they are experiencing acute stress, chronic stress, or distress as well as what is causing the stress, which are defined below. The overall top causes of stress within people in the US is shown within Figure 4.
Acute Stress: Stress associated with the flight or fight response.
Chronic Stress: Stress associated with daily life.
Distress: Stress associated with a negative connotation within daily life. Some examples include divorce, punishment, injury, negative feelings, financial problems, and work difficulties (Baum 1990).
| Top Causes of Stress in the U.S. | ||
| Cause | Factors | |
| 1 | Job Pressure | Co-Worker Tension, Bosses, Work Overload |
| 2 | Money | Loss of Job, Reduced Retirement, Medical Expenses |
| 3 | Health | Health Crisis, Terminal, or Chronic Illness |
| 4 | Relationships | Divorce, Death of Spouse, Arguments with Friends, Loneliness |
| 5 | Poor Nutrition | Inadequate Nutrition, Caffeine, Processed Foods, Refined Sugars |
| 6 | Media Overload | Television, Radio, Internet, E-Mail, Social Networking |
| 7 | Sleep Deprivation | Inability to release adrenaline and other stress hormones |
Figure 4: The results of a survey conducted in 2014 by the American Institute of Stress and the American Psychological Association looking at the top causes of stress within the US.
STRESS RESPONSE
The conceptualization of stress is viewed involving four steps: exposure to a particular task or situation, stress arousal (perceiving the situation or task to be challenging or threatening), coping psychologically with the stress; and adjusting to stress behaviorally, physiologically, and psychologically (Hobfull 1988). Cortisol, DHEA, sympathetic nervous system, parasympathetic nervous system, oxidative stress, anti-inflammatory cytokines, and inflammatory cytokines all play a role within the physiological aspect to coping with stress (McEwen 2008).
Behavioral Response: Removing self from situation, seeking an environment which decreases stress, as well as hiding from potential predators.
Autonomic Nervous System Response: Flight or fight response. The autonomic nervous system affects a diverse number of biological systems, including the cardiovascular system, the gastrointestinal system, the exocrine glands and the adrenal medulla. The results are short term changes in heart rate, blood pressure and gastrointestinal activity, and others (Moberg 2005).
EFFECTS OF CHRONIC STRESS
An experiment looked at the effects of chronic stress on hippocampal-dependent functions within mice. The mice were given a variety of spatial navigation tasks at a variation of tasks. It found that mice which were considered to have “chronic stress” experienced impairment within spatial reference memory and spatial working memory. Overall, the experimenter concluded that chronic stress alters brain regions, specifically the hippocampal spatial ability (Conrad 2010).
Additionally, there is stress-associated immune dysregulation. Interactions between the central nervous system, the endocrine system, and the immune system must be studied to better understand this dysregulation. Lymphocytes, monocytes, or macrophages and granulocytes, exhibit receptors for many neuroendocrine products of the hypothalamic pituitary -adrenal (HPA) and the sympathetic-adrenal medullary (SAM), both HPA and SAM are pathways which can alter immune function. Binding of neuroendocrine products, such as cortisol and catecholamines from stress to receptors can lead to changes in cellular trafficking, proliferation, cytokine secretion, antibody production, and cytolytic activity.
Chronic stress as well as stress inducing events can have a variety of effects on immunity. To view these effects an experiment was preformed which gave subjects a variety of vaccines and viewed their body defense response. It found that when administering Hepatitis B vaccines within students, stress and social support affected the virus-specific antibody and T-cell responses. Additionally, within caregivers, it found that they had a lower antibody response when given the influenza vaccine. This experiment discovered that those who had lower responses to vaccines also experienced more frequent as well as longer lasting illnesses. Therefore, those who experience stress are more likely to have poorer immune responses to vaccines and are thus more susceptible to illnesses (Padgett 2003).
WHY DO WE EXPERIENCE THESE EFFECTS WITH NATURE?
Hamilton discusses two potential theories as to why nature has this “restorative” power on human health: stress reduction theory (SRT) and attention restorative theory (ART).
Stress Reduction Theory
Before industrialization, landscapes which contained water and vegetation were the most beneficial to survival for human. Stress reduction theory believes the positive emotions that we feel when we view these landscapes are evolutionary and innate so that humans had the urge to stay within these types of landscapes. These landscapes effect human cognitive processes without even needing to think about it (Hamilton 122).
Attention Restorative Theory
This theory states that people shift their attention to nature when in its presence, which then shifts their attention away from other distractions. According to this theory, there must be four things that landscapes must contain to effectively direct people’s attention away from other distraction as well as have restorative effects. First, the person must feel as though they are immersed in the landscape. Additionally, the person must feel as though they have escaped their daily life stressors. Next, the environment must be fascinating to the person. Finally, the landscape must be compatible to the person (Hamilton 124).
MY STUDY
The overall goal of my study is to look at the effect of being outside has on human stress. It is hypothesized that if someone goes outside when they are feeling distressed, then they will be calmer.
Within the experiment, twenty participants will be asked to keep a journal for two weeks. The participants will be randomly assigned to either an inside or outside group by flipping a coin (heads = inside, tails= outside). All the participants will be asked to document when they are feeling stressed, what is causing their stress, as well as their heart rate when experiencing these emotions. The participants who landed on tails will be asked to step outside for five minutes when they are feeling stressed. Upon returning inside, the participants will document the weather, what they did and saw outside, ranking their stress on a scale from one to five, as well as their current heart rate within their journal, as seen in Figure 5. The participants who landed on heads will be asked to wait inside for five minutes after feeling stressed. After the time, the participants will be asked to rank their stress on a scale from one to five, document their heart rate, as well as what they did/saw inside within their journal, as seen in Figure 6.
Figure 5: The journal outline given to participants which are asked to go outside.
Figure 6: The journal outline given to participants which are asked to stay inside.
The heart rates before and after going outside between the two groups of participants will then be compared using a T – test. A T-test was selected to see if there is a significant difference in means between the heart rates of those who did and did not go outside. The null hypothesis is that there is no significant difference between the groups of participants. If the P-value is equal to or less than 0.05 then the null hypothesis will be rejected. Therefore, there is a significant difference in the heart rates between the two groups. On the other hand, if the P-value is greater than 0.05 then the null hypothesis will fail to be rejected. Therefore, there is no significant difference in the heart rates between the two groups.
I based this experiment on Ulrich’s study. To begin, I randomly assigned participants to groups, like Ulrich, to avoid bias. Additionally, like Ulrich’s study, I have a large amount of data which is also beneficial to avoiding bias. Within Ulrich’s study, he had the participants experience a variety of different everyday stressors. Similarly, in my study the participants will be coming from a variety of different backgrounds and thus a variety of different stressful situations (which they will document within their journal). Additionally, Pretty had the participants engage in different ways within nature. Similarly, in my study the participants are asked to document what they did and saw when they were asked to step inside and outside. Doing so, I will be able to take into consideration their engagement within nature (whether they are only viewing, being present and viewing, or being present and doing activities within nature). Finally, within both of our studies we are collecting heart rate, which is a signifier of stress within the human body (Wolf 2014).
RESULTS
At the beginning of the experiment, I had all participants take their resting heart rate. The mean resting heart rate, between both the inside and outside group, was 64 beats per minute. The average resting heart rate for participants that went outside was 65.5 beats per minute and the average resting heart rate for participants that stayed inside was 65 beats per minute. The average heart rate after the participants returned from outside was 69 beats per minute and the average heart rate after the participants remained inside was 71.5 beats per minute. The average difference in resting heart rate and heart rate after going outside was 3.5 beats per minute with a standard deviation of 1.5. The average difference in resting heart rate and heart rate after remaining inside was 5.5 beats per minute with a standard deviation of 2. After performing a T-test, I received a T value of 2.5298 and a P value of 0.0210
Some additional findings that I found interesting was that within participants that went outside, their average heart rate was 67.5 beats per minute when it was sunny outside and 70 beats per minute when it was cloudy outside. Additionally, within participants that went outside, those who interacted with nature (3rd level of engagement) had an average heart rate of 67.8 beats per minute and those who were just present in nature (2nd level of engagement) had an average heart rate of 69 beats per minute.
Within patients that stayed inside, those who looked outside of windows had an average heart rate of 64.5 beats per minute, while those who did not look outside had an average heart rate of 65.5 beats per minute.
DISCUSSION
With a P-Value of 0.0210 < 0.05, the null hypothesis will be rejected. Therefore, there is a significant difference in heart rate between participants going outside and staying inside. This leads me to believe that being outside and around nature is better at reducing stress than remaining inside. This supports the idea that simply being in the presence of nature and being outdoors can positively impact mental health. Additionally, due to the findings regarding the different levels of engagement, I believe that all levels of engagement within nature is beneficial to mental health. Similarly, to Pretty’s findings, I found that the third level of engagement within nature was the most beneficial to health and stress levels.
Due to my findings on sunny weather being more effective at reducing heart rate, I believe that more future research can be preformed looking at the effects that certain weather conditions can have on mental health. I believe that this information could be beneficial to those with mental health so they can choose a better location to live based on weather. Additionally, they can better plan on being around nature during a specific weather to get the most benefits.
WHY IS THIS IMPORTANT?
Since the study finds that being in nature is beneficial to stress, this will be a way that everyone can positively help their mental health free of cost. It is important to manage our stress to maintain health such as maintaining a strong immune system. According to the American Institute of Stress, most Americans spend 90% of their lives indoor (“How Being Outdoors…” 2020). Therefore, spaces can be set up to include more nature to help peoples’ mental health. For example, offices can include more windows and more pictures depicting nature. Homes can also include more plants. Additionally, incorporating more green spaces within cities has the potential of improving health.
Works Cited
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