Trauma can be a consequence of a single event, an extended series of events, or a set of circumstances that are physically or emotionally harmful. These traumatic experiences are often threatening and can have lasting adverse effects on an individual’s functioning and well-being [1]. People who have faced such traumatic incidents, especially during their childhood, are at a significantly higher risk of enduring mental health challenges throughout their lives [2].

One common psychological condition that stems from trauma is post-traumatic stress disorder (PTSD). This disorder is often characterised by increased anxiety, a state where the individual’s stress response is displaced even when no immediate threat or stressor exists [3].

The stress response is a complex, coordinated reaction to threatening stimuli. Key indicators of this response are avoidance behavior, heightened arousal and vigilance, activation of the sympathetic nervous system, and the release of cortisol, a stress hormone, from the adrenal glands.

The key to understanding and managing anxiety lies in unraveling the intricate workings of the brain’s stress response [3]. The hypothalamic-pituitary-adrenal axis (HPA) plays a vital role in this, facilitating our humeral reaction to stress and coordinating suitable somatic-motor, humoral, and viscero-motor responses. Essentially, the HPA axis governs the secretion of cortisol from the adrenal gland [5]. This intricate chain of reactions involves several stages:

• An increase in blood level of adrenocorticotropic hormone (ACTH) triggers the release of cortisol from the adrenal cortex.
• ACTH is released by the anterior pituitary gland in response to corticotropin-releasing hormone (CRH).
• CRH is the chemical messenger linking the paraventricular nucleus of the hypothalamus and the anterior pituitary gland.
• ACTH is carried in the bloodstream to the adrenal gland, which is prompted to release cortisol.
• Finally, cortisol contributes to the body’s physiological response to stress.

In simpler terms, the CRH-containing neurons in the hypothalamus play a significant role in regulating our stress response. For example, studies on mice have shown that when CRH is over-expressed, they display increased anxiety-like behaviors. Conversely, when the receptors for CRH are genetically removed, the animals exhibit less anxiety-like behavior compared to regular mice [6].

Moreover, the amygdala and hippocampus, two regions in the brain, exercise control over CRH neurons. The amygdala is crucial for fear responses; sensory information enters the basolateral amygdala, is processed, and passed on to neurons in the central nucleus of the amygdala. Activation of this central nucleus triggers the stress response [7]. Additionally, neurons in the bed nucleus of the stria terminalis (BNST), also known as the ‘extended amygdala,’ activate the HPA axis and the stress response [8].

On the other hand, the hippocampus inhibits CRH release when circulating cortisol levels get too high, thus providing a check on the system [9]. Prolonged exposure to chronic stress, resulting in consistently high levels of cortisol, can damage the hippocampal neurons [10], leading to memory issues and impairments in emotional regulation. This has been observed in people suffering from PTSD [12].

Anxiety disorders have been linked to hyperactivity of the amygdala and diminished activity of the hippocampus, often caused by high levels of circulating cortisol, which can negatively affect human cognition.

So where does Shinrin Yoku, or forest bathing, come into this picture? Forest environments have been proven to act positively on the endocrine system, reducing blood cortisol levels [4]. Practicing Shinrin Yoku can serve as a form of preventive medicine against stress and can induce a relaxed state.

In conclusion, trauma and stress can have profound impacts on an individual’s mental health. Understanding the complex reactions and mechanisms involved can help provide better care and preventive measures. Among these, Shinrin Yoku stands as a powerful, nature-based strategy to combat stress and enhance well-being.

References
[1] Center for Substance Abuse Treatment (US). (2014). Trauma-Informed Care in Behavioral Health Services. Substance Abuse and Mental Health Services Administration (US). 

[2] Devi, F., Shahwan, S., Teh, W. L., Sambasivam, R., Zhang, Y. J., Lau, Y. W., Ong, S. H., Fung, D., Gupta, B., Chong, S. A., & Subramaniam, M. (2019). The prevalence of childhood trauma in psychiatric outpatients. Annals of general psychiatry, 18, 15. https://doi.org/10.1186/s12991-019-0239-1 

[3] McEwen, B. S., Bowles, N. P., Gray, J. D., Hill, M. N., Hunter, R. G., Karatsoreos, I. N., & Nasca, C. (2015). Mechanisms of stress in the brain. Nature neuroscience, 18(10), 1353–1363. https://doi.org/10.1038/nn.4086 

[4] Park, B. J., Tsunetsugu, Y., Kasetani, T., Kagawa, T., & Miyazaki, Y. (2010). The physiological effects of Shinrin-yoku (taking in the forest atmosphere or forest bathing): evidence from field experiments in 24 forests across Japan. Environmental health and preventive medicine, 15(1), 18–26. https://doi.org/10.1007/s12199-009-0086-9 [

5] Herman, J. P., McKlveen, J. M., Ghosal, S., Kopp, B., Wulsin, A., Makinson, R., Scheimann, J., & Myers, B. (2016). Regulation of the Hypothalamic-Pituitary-Adrenocortical Stress Response. Comprehensive Physiology, 6(2), 603–621. https://doi.org/10.1002/cphy.c150015 

[6] van Gaalen, M. M., Stenzel-Poore, M. P., Holsboer, F., & Steckler, T. (2002). Effects of transgenic overproduction of CRH on anxiety-like behaviour. The European journal of neuroscience, 15(12), 2007–2015. https://doi.org/10.1046/j.1460-9568.2002.02040.x 

[7] Etkin, A., & Wager, T. D. (2007). Functional neuroimaging of anxiety: a meta-analysis of emotional processing in PTSD, social anxiety disorder, and specific phobia. The American journal of psychiatry, 164(10), 1476–1488. https://doi.org/10.1176/appi.ajp.2007.07030504 

[8] Lebow, M., Chen, A. Overshadowed by the amygdala: the bed nucleus of the stria terminalis emerges as key to psychiatric disorders. Mol Psychiatry 21, 450–463 (2016). https://doi.org/10.1038/mp.2016.1 

[9] Dahmen, B., Puetz, V. B., Scharke, W., von Polier, G. G., Herpertz-Dahlmann, B., & Konrad, K. (2018). Effects of Early-Life Adversity on Hippocampal Structures and Associated HPA Axis Functions. Developmental neuroscience, 40(1), 13–22. https://doi.org/10.1159/000484238 

[10] McEwen, B. S., Nasca, C., & Gray, J. D. (2016). Stress Effects on Neuronal Structure: Hippocampus, Amygdala, and Prefrontal Cortex. Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 41(1), 3–23. https://doi.org/10.1038/npp.2015.171 

[11] Lupien, S. J., Juster, R. P., Raymond, C., & Marin, M. F. (2018). The effects of chronic stress on the human brain: From neurotoxicity, to vulnerability, to opportunity. Frontiers in neuroendocrinology, 49, 91–105. https://doi.org/10.1016/j.yfrne.2018.02.001 

[12] Logue, M. W., van Rooij, S., Dennis, E. L., Davis, S. L., Hayes, J. P., Stevens, J. S., Densmore, M., Haswell, C. C., Ipser, J., Koch, S., Korgaonkar, M., Lebois, L., Peverill, M., Baker, J. T., Boedhoe, P., Frijling, J. L., Gruber, S. A., Harpaz-Rotem, I., Jahanshad, N., Koopowitz, S., … Morey, R. A. (2018). Smaller Hippocampal Volume in Posttraumatic Stress Disorder: A Multisite ENIGMA-PGC Study: Subcortical Volumetry Results From Posttraumatic Stress Disorder Consortia. Biological psychiatry, 83(3), 244–253. https://doi.org/10.1016/j.biopsych.2017.09.006

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Venture on a memorable path with our 10-week Shinrin Yoku Guide Training program accredited by Shinrin Yoku Association . This journey merges the accessibility of online learning with an enriching immersion in the serene forests of Japan. 🌳🇯🇵

Embark on your online adventure with flexible scheduling (GMT-3, Argentina Time) 🖥️🌐:
🌱 July 21 (Fri), 12 PM
🌱 July 28 (Fri), 2 PM
🌱 August 4 (Fri), 8 AM
(More dates available online!)

Continue your transformative journey with a 5-day retreat nestled in the peaceful woodlands of Nara, Japan 🏞️🎑:
🍂 October 2-6, 2023
🍂 October 9-13, 2023

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The Mindful Tourist
森の心・人の心
Journey Through Life With the Wisdom of the Forest