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It is often said that stress is bad for health. Oftentimes, people don’t fully understand how true this is. Stress, whether acute or chronic, can cause a cascade of events inside the body which can damage every system.

Scientists have studied the human stress response from cavemen to modern society. Whether the brain perceives a threat from being chased by a tiger, mourning the loss of a loved one, or from struggling with a mountain of unpaid bills, the resulting physiological response is the same.

When a person perceives a sensory threat (visual, audio, tactile, etc.), the amygdala is the first responder within the brain. The amygdala processes the danger and sends a distress call to the hypothalamus, which operates like the brain’s command center. It communicates to the rest of the body via the autonomic nervous system (ANS) by sending signals to major organs to release or stop releasing certain hormones. The ANS controls involuntary processes like breathing, heart rate, digestion, respiration, etc. Most of the time, the ANS is supposed to be in a balanced state called the parasympathetic response. During this time, all bodily functions are operating evenly and calmly, not in a stress/survival mode. It is often referred to as the “rest and digest” response because the body is prioritizing resting, digestion, reproduction and healing. When the hypothalamus releases distress signals, a series of events happen very quickly through the Autonomic Nervous System. In order to face an oncoming threat, the adrenal glands (located near the kidneys) release a flood of responsive hormones like cortisol and adrenaline to prime the body. These hormones help trigger what is known as the sympathetic response in the ANS. It is also often referred to as “fight-or-flight” mode. During a sympathetic response, the body increases respiration, heart rate and blood flow to the brain and muscles, while decreasing nonessential functions such as digestion, sleep, healing, immune response, and reproduction. This state allows the person to focus on surviving the stressful situation at hand, whether they need to flee from a dangerous animal or fight through a frightening public speaking presentation. When the danger or stressful event passes, the adrenal glands are told to stop releasing stress hormones and instead release calming hormones such as acetylcholine to slow the heart rate and bring the body back into a parasympathetic state to recover.

Unfortunately, modern society is not kind to the Autonomic Nervous System. While humans are not often facing acute and life-threatening dangers like our ancestors before, they do often face constant micro-stressors. In a state of constant stress, the body can get stuck in fight-or-flight mode. Combat veterans and abuse victims are prime examples of people in sympathetic dominance; less appreciated examples are single parents, financially struggling people, students, and people with high-stress jobs. Being stuck in a chronic state of fight-or-flight can cause insomnia, digestion issues, autoimmune disease, frequent illness, slow healing, heart disease, and even cancer. If the body is prioritizing basic survival functions for too long, other bodily functions will slow or even stop completely. The adrenal glands may eventually struggle to keep up with producing any kind of hormones needed to function properly, causing a condition called Adrenal Fatigue. Chronic stress is harmful at a cellular level as well; oxygen feeds mitochondria, but stress may cause that oxygen to be depleted or directed elsewhere. Without adequate oxygen, mitochondria may struggle to produce ATP, the energy source for all cellular processes, which can lead to widespread cell death, inflammation, and more destruction throughout the entire body.

Hyperbaric Oxygen Therapy has been studied on patients with sympathetic dominance using heart rate variability (HRV) monitoring. This research has shown that hyperbarics can help calm the ANS and cause the signals from the hypothalamus to change from a sympathetic response to a parasympathetic response. Researchers can watch in real-time as patients switch from fight-or-flight over to rest-and-digest during a hyperbaric treatment. On a larger scale, research has been done on patients with Post Traumatic Stress Disorder and hyperbarics. Many of the studies confirmed positive responses for these patients, sometimes showing a full recovery. Increasing oxygen levels means more food for the cells as well. Mitochondria can produce adequate ATP to correct or replace damaged cells and tissues. Once the brain is able to stop sensing a constant threat, healing can take place everywhere, even in areas the patient doesn’t expect such as fatigue, muscle or joint pain, dysfunctional immune system, and many more.