We are all confronted with stress in our daily lives and often ask ourselves how we can reduce it or keep its effects within a healthy limit.
Forest bathing could be an effective tool here. Called "Shinrin Yoku" in Japanese, the activity is gaining more and more attention in science and research. In addition to many health benefits, the natural environment of the forest is also said to be able to measurably reduce stress. To what extent this is possible, measurable and relevant to us is what we want to look at in this blog post.
What actually is stress?
Stress is omnipresent in our lives. In the morning before work, it builds up unnoticed due to time pressure. A bulging calendar accompanies us through the office day until late afternoon or even evening. The so-called family business can also become an additional burden. With an already habitual stress level, we fall exhausted into bed, where our thoughts already turn to the tasks of the next day.
We then urgently need time for self-care, a free weekend, or even a wellness vacation. But why actually? Why are we so stressed and why is this a problem for body and mind?
The term stress actually comes from mechanics, where it describes a load that leads to a structural deformation. This is how it has been applied to humans: an external stress leads to changes in our body, but unlike in engineering, the stress we feel is not proportional to the external stimulus but varies from individual to individual. (1)
Between load and overload
This is, among other things, from the allostatic loadas it is called in science. This load describes the response in the body, whether by hormones or nerves, to external stimuli that a person personally perceives as stressful. These stimuli can of course be environmental factors as well as psychological perceptions. (2)
In itself, this is not bad, the body reacts to stimuli and adapts functions to better cope with them. It then becomes problematic with allostatic OVERLOAD. Then the system is overloaded and can no longer react appropriately. This can be due to lack of adaptation to repeated stressful stimuli, constant activation of the system, lack of relaxation after the stimulus is over, or even a fault in the system so that it cannot respond to the stimulus. (2)
This overload is especially problematic because it is associated with many physical ailments and diseases. These include cardiovascular diseases, such as strokes. Burn out, depression, anxiety disorders, schizophrenia, reduction of mental and physical abilities in the elderly, worse diabetes outcomes, and more can result.
If one then treats these consequences with medication, further stress is created for the body, the so-called pharmacological allostatic load, which can be further counterproductive under certain circumstances. It is therefore best to treat the problem at its cause and this calls for interdisciplinary medical approaches and lifestyle changes! (2)
An adjustment of the lifestyle should actually be in the first place. Anyone who is under pressure 24/7, be it from work, household or mental stress, should read on here carefully. Because it is now quite clear that stress is not a sign of weakness or effeminacy, but seriously damages our health.
Our body's stress response can be influenced and that's where forest bathing comes in. And here's the spoiler right away: Yes, forest bathing can reduce stress! In order to understand whether and how this works, let's take a brief look at how stress can be measured in the body and how these biological indicators are also related to diseases.
Digest and fight?
The so-called "autonomic nervous system" lies dormant within us. This is basically divided into two states or two modes of action. The sympathetic nervous system stands for "fight or flight" and is activated during stress. The body sees itself fighting for survival through danger and ramps up functions to be able to flee or fight: more blood is pumped to the muscles, the heart beats faster, the breathing rate increases.
On the other side is the parasympathetic nervous system. This is active when we are not stressed and regulates many important functions, such as the digestive or immune system. This may also explain why permanent stress then manifests itself in digestive problems or a cold.
Stress is permanently too high and the balance between sympathetic and parasympathetic nervous system is no longer correct. An important mediator for the parasympathetic nervous system is the so-called vagus nerve: a network of neurons that regulates, for example, this redistribution of blood to the digestive tract, the relaxation of the pulse and other important functions.
A healthy autonomic system is adaptive and can anticipate, buffer and respond to environmental demands! (3-5)
Negative bias: Stress is the processing of the perception of danger or safety. When it is unclear whether a situation is dangerous, the brain prefers to play it safe and prepare for the worst. It wants to ensure our survival.
Is there a snake or a stick lying on the ground in front of me? At first, we are startled, feel hot and our pulse rate rises. Until we recognize the stick and signal the all-clear.
In modern everyday life, constant perception of danger leads to overload. Heavy traffic, permanent pressure from management and many other small and big stressors, keep us always easily on tension. Chronic stress develops.
Many people cannot adapt to this and are always on the alert, which leads to health damage. By the way, the body does not really distinguish between physical, psychological stress and real environmental influences such as noise. (5)
How to measure stress:
In general, stress measurement can take place through two systems, both of which we want to look at. On the one hand, you can look at the autonomic nervous system, which is the sympathetic nervous system and the parasympathetic nervous system, and on the other hand, you can look at the HPA axis. The hypothalamic-pituitary-adrenal axis. The latter is a central channel through which the brain initiates the stress response in the body. Here, the hormone cortisol is the messenger. (1)
Our stress hormone
Let's take a look first Cortisol an. A steroid hormone secreted by the body in a stress response. It is produced via a complex pathway in the hypothalamic-pituitary-adrenal axis from prohormones and factors in the adrenal cortex and then enters the bloodstream. Cortisol affects the body and brain in general. Thus, it affects not only the current stress response, but also future stress responses.
Cortisol is an extremely important hormone, which we also need for our sleep-wake rhythm, for example. Cortisol in the blood is highest in the morning when we wake up, and is also one of the reasons why we can become active in the morning. It peaks about 30 minutes after getting up and then, ideally, steadily decreases over the course of the day into the evening. In addition, during the day we have repeated "bursts" of cortisol, due to spontaneous stress reactions, which are healthy if they also drop afterwards. If we are very stressed during the day, this drop is weakened and the daily variation in the cortisol profile decreases, which can seriously affect our sleep-wake rhythm. Chronically high levels of cortisol also have a neurotoxic effect and therefore a negative impact on mood, cognitive function and the stress response itself. (1)
Cortisol can be measured in saliva and in blood, whereby saliva is the more accurate variant. Of course, it is important to relate the values to the personal morning values and to observe the daily rhythm. Then there are also a few people, mainly women, in whom no cortisol reaction is measurable at all in studies.
But on cortisol and the other related hormones, there will be another blog post.
The heart is not a metronome
Another important tool is the Heart rate variability. This is a value that describes how the pulse increases and also decreases again; to what extent the body is able to react appropriately to a stress stimulus and also to calm down again afterwards.
It results from interaction of the sympathetic and parasympathetic nervous systems, respiration, pressure receptors and rhythmic fluctuations.
It is good to have high variability. Low variability represents poor recovery of cardiovascular, mental and immunological response to stressors after termination of the trigger. (4). This is associated with many diseases, general mortality, mental illnesses such as anxiety disorders and depression but also asthma, COPD, and gastrointestinal disorders. (6)
High heart rate variability, on the other hand, is associated with increased cognitive performance, emotion regulation, and behavioral control (4). All in all: a healthy heart is not a metronome! (7)
With age, the variability often decreases because the regulation of the autonomic nervous system is limited. However, this predictable course is influenced by stress and lifestyle. (4)
When measuring the variability, one can then also look at different ranges. The high frequency range is the most interesting here for stress research because it describes the activity of the parasympathetic nervous system and is influenced by the vagus nerve and breathing. Low variability in the high frequency range is associated with stress, panic, anxiety and worry, but also with depression, anxiety, impulse control disorder, substance abuse, psychosis and generally low mood. (4,8)
The longer these measurements are taken, the more accurate they become, but as little as 5 minutes can provide a lot of information. The heart rate variability tool is also being used more and more in the personal health industry, with personal heart rate monitors determining variability and showing you how your stress levels have been throughout the day. (6)
Forest bathing and stress:
Forest bathing can definitely reduce stress. This has been evaluated by many studies, meta-analyses and systematic reviews using cortisol, heart rate variability, but also questionnaires and personal assessments.
Research findings:
Meta-analyses and systematic reviews look at the results of many studies and evaluate them qualitatively or mathematically in order to be able to make generally valid statements. And then there are also the so-called "umbrella reviews". These look at several systematic reviews and meta-analyses and then condense the results of these once again. These umbrella reviews have come to the conclusion that forest bathing or a natural environment reduces stress. (9-11): .
Forest bathing was able to achieve relaxation effects in large population studies with up to 485 participants. For example, stress hormones were reduced and blood pressure and pulse were lowered. The activity of the parasympathetic nervous system and the vagus nerve could be increased. (9)
Recent meta-analyses and systematic reviews that have not yet made it into Umbrella Reviews also subscribe to these findings and show, among other things, that forest bathing can increase heart rate variability, especially in the high-frequency range, and reduce cortisol (12,13).
Heart rate is considered a marker of our overall health and also a marker of stress levels in the body. It is measured in heartbeats per minute. The pulse is the resulting expansion of the arteries, such as we can feel and count on the wrist. In healthy people, these values are almost the same, but in diseased cardiovascular systems they can sometimes vary due to weaknesses, blockages or stiffening.
In fact, forest bathing can have a positive effect here and influence our heart health. (11,13-15)
Here, a study indicates that pulse may be reduced in middle-aged adults with prehypertension or hypertension, but not in young or old adults. (16)
On the exciting topic of heart rate variability and regeneration, however, there will be more in-depth podcasts and also interviews with experts in the Rich Headroom.
Study design
Different methods are used in the studies: Sometimes the subjects sit in the forest, sometimes they walk, sometimes simply the time spent per week in the forest is compared, and then the specific forest bathing, the conscious perception of the forest atmosphere is also looked at. This is then compared with a stay or walk in the city, with other stress therapy, such as cognitive behavioral therapy, or simply the before and after values are considered. All these variants have different advantages and disadvantages, of course. What is clear, however, is that the results regarding stress are surprisingly consistent. In particular, it has been shown that walks in nature are clearly superior to walks in an urban environment. (14,17-19).
How does forest bathing actually work properly?
The easy option is to go to the forest and spend time there as the mood takes you. The more often the better. But even one visit a week will show its effect. It's as easy as that!
But of course there is also a version for the ambitious biohackers among you. Here are a few exciting study results.
Two research groups studied how mindfulness and nature together affect stress. The results show that mindfulness combined with spending time in nature provides stronger stress reduction than either alone. The traditional "Shinrin Yoku" practice is based on exactly this connection. (20,21) So when we go into the forest, mindfulness further supports the process of stress reduction. This means that it would be better to go without podcast, phone call, business conversation or music in the ears and immerse yourself in nature. Feel, look, smell, attack, observe. All of this additionally relaxes us, and engaging with the details of a leaf or a handful of soil, is a wonderful mindfulness exercise and a way to explore our environment. It also trains us to be in the moment and not think about the next task: an interruption of the thought carousel around office life and family management.
Of course, the factor of exercise also comes into play. We know that exercise and sport alone can reduce stress. In fact, exercise has proven to be particularly helpful in the case of chronic stress.
With acute stress, however, this looks a little different. The leisurely stay in nature and the sight of trees, meadows and leaves has proven to be better here. (22) But these are probably details and their different effects are also difficult to prove.
Between walks in nature and in the urban environment, however, it becomes apparent that not only the movement is relevant, but also the surroundings. Forest simply calms.
Whether sitting, walking or exercising in the woods, all variations relax and help us cope with stress. (23) That is probably the key message.
Do I have to go to the forest or is a park enough?
A natural environment that isolates you from city noises and smells is certainly best. A "real forest" is probably the best choice and has the strongest effect. Forest conveys a tranquility that even a large city park struggles to achieve. But of course, accessibility is an important issue.
My motto: "Every tree counts"! I'd rather have a quiet lunch break under a handful of birch trees in front of the office building than eat in the canteen under artificial light and with bad air.
Even with only one tree, the air is a little better and there is a good chance that one or more birds will be inside. This makes for a woodsy feeling, at least acoustically.
We will look at which forests, tree species and time of year is best for us in an upcoming blog article on forest bathing.
Relaxing even easier with water
Bluespace, i.e. lakes or rivers, also have a stress-reducing effect, by the way, even though there is no forest involved. (24) Of course, the combination is ideal. Take a look at my blog about the "Green Lake". Or even better, visit it in Styria (Austria). One of my 10 favorite places to relax.
And how long should I bathe in the forest?
The International Forest Therapy Handbook (25) recommends 2-4 hours stay. That this duration is not feasible for many in everyday life is completely clear to me and fortunately not absolutely necessary! Already from 15 minutes a recovery effect could be determined and according to the participants the relaxation lasted up to 5 days. In total, 2h per week, divided into small bites, is really great. (9,17,26)
The limits of research
Of course, I also want to educate you about the limitations of research in this area. As I've already told you, the study designs are highly mixed and don't necessarily meet the highest scientific standards. It is difficult to blind participants, how am I supposed to keep secret from someone that they are looking at a city or a forest. Also, as we have already seen with cortisol, this hormone is subject to strong daily and hourly fluctuations and does not always behave perfectly as it does in the laboratory, which is why statements about cortisol have the least significance in this regard. Particularly detailed studies, which would be necessary in this regard, are still lacking. Many studies also consist of very small numbers of subjects, which is partly due to the fact that there are no large financial revenue opportunities behind forest bathing, which is why companies rarely make investments and drive research here. A greater diversity of participants is also desired by researchers in this area.
Last, the "nature positive bias" is described, which comes into play in the selection of study participants, as well as the anticipation of participation. People who feel comfortable in nature are more likely to sign up for such studies and already look forward to the announced walk in the forest. This can be compared with studies on nutrition, in which mostly people with an interest in healthy nutrition also participate. (9,12,17,21,27)
With all this information in mind, I still see the impact of forest bathing as more than positive. At practically zero cost, we can create a balance in our daily lives in a healthy and enjoyable way. We can counteract stress and contribute something to our mental health.
If you want to learn more about forest bathing, sign up for my newsletter. There are 6 more blog posts and podcasts to follow on various topics related to forest bathing. From the psychological to the immunological effect!
Richard Staudner
The Optimizer
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Sources
McCorry LK. Physiology of the autonomic nervous system. Am J Pharm Educ. August 15, 2007;71(4):78.
25 Kotte D, Li Q, Shin WS, Michalsen A. International handbook of forest therapy. 2019.
