Your brain is constantly scanning its environment for signs of danger, ready to activate bodily processes and reflexes to keep you safe from anything it perceives as a threat. When danger is detected, all animals, from mice to humans, respond physically with an almost instantaneous sequence of hormonal and physiological changes preparing them to run or battle for their lives.

It was the Harvard University physiologist, Walter Canon, who first used the term fight-or-flight to describe this instinctual, biological reaction of all animals to fear back in the 1920s. Now, this phenomenon is also commonly referred to as the stress or fear response.

This life-saving response was a good thing which helped our ancestors survive, but it was only meant to activate infrequently in life or death situations. However, this trigger still exists in your brain today, and kicks in too frequently for common occurrences, like getting stuck in traffic, a work deadline, or an unexpected bill. Because of the accompanying bodily reactions, a frequent or chronic stress response has negative health consequences for your brain and body over time. However, the good news is that there are many ways you can turn down your stress response.

The Sympathetic Nervous System

Your sympathetic nervous system (SNS) manages your body’s stress response. When your brain initiates it, your body quickly increases your heart rate and breathing, dilates the pupils, redirects blood flow to your muscles, shuts down your brain’s frontal lobe, and releases stress hormones, cortisol, adrenaline, and noradrenaline. The parasympathetic nervous system is the “brake” that helps calm your body once the threat has faded.

Unlike other animals, humans are unique because danger doesn’t have to be imminent or actually happening to warrant a SNS response. Often, our thoughts are enough to trigger a stress response when there isn’t any real threat present. Our big sophisticated brains can go into high alert when just remembering, anticipating, or imagining something upsetting or scary. You can put yourself into a full-blown panic when there’s no actual danger.

Thankfully, the converse is also true. You can work yourself out of a stressful state solely with your mind and thoughts.

Benefits of the Stress Response

In actuality, stress is not all bad. For example, the nervous tension you feel when going on a first date, speaking in front of a crowd, or starting a new job is called eustress. The stress created by these situations can actually be helpful, making sure you perform better in circumstances where you are under pressure to do well.

On a biological level, stress is a normal physical response that happens whenever you ask your body to adapt or respond in some way. It’s an essential part of living. Technically, you are stressing your body when you ask it to get up out of a chair, learn a new skill, or go for a run. When stress is not severe or chronic and neurons are given time to recover, connections and pathways in your brain actually become stronger, and stress is not a bad thing. The problem arises when your brain sounds the alarm too often, and stress becomes a constant state for your body, and your sympathetic nervous system is always “on.”

wild animals in the desert, giraffe, lion, deer

When a Good Thing Goes Bad: Toxic Stress

Robert M. Sapolsky, a Stanford University biologist, explains in a TED talk, The Psychology of Stress:

“What stress is like for 99% of the beasts on this planet is three minutes of screaming terror on the savannah after which either it’s over with or you’re over with. We turn on the identical stress response for a thirty-year mortgage.”

Toxic stress is prolonged exposure to high levels of stress, particularly in situations where an individual lacks the necessary support and coping skills to deal with it. Unfortunately, many events can lead to toxic stress, such as childhood trauma, adverse life events, or ongoing environmental and life circumstances, and have significant adverse consequences for your mind and body.

Toxic Stress Damages Your Brain

Too much stress long-term harms your physical brain and it’s functioning. A system that was originally designed to help our species is now a threat to it in many ways. Chronic stress makes it hard to remember, concentrate, and make decisions and increases your risk of anxiety, depression, Alzheimer’s and many mental illnesses. Here’s how it damages your brain:

  • Cortisol initially helps your brain by increasing synapse strength in the hippocampus, which is vital for memory, as well as the flow of some other helpful neurochemicals. However, it eventually suppresses these same things when chronic.
  • Too much stress causes physical damage to the hippocampus, vital for memory, from a surplus of glutamate, a signaling neurotransmitter, and cells die resulting in memory loss.
  • In time, cortisol wires pathways between the hippocampus and amygdala, forming a vicious loop creating a brain that’s in a constant state of fight-or-flight arousal.
  • The dendrite branches at the end of brain cells pull back, complicating signal transmission, and interrupting neurogenesis, the birth of new brain cells.
  • While stress is shrinking dendrites, killing brain cells, and preventing new cell growth in the hippocampus, it’s sending the amygdala, the brain’s fear center, into overdrive. Stress causes the amygdala to create more connections, which keep firing and keep the cortisol flowing — even though there’s already an abundance. The more the amygdala fires, the stronger it gets. Soon, a persistent feeling of stress, anxiety, and fear predominates in your brain, regardless of what’s happening. Your amygdala is now running the show instead of other “intelligent” brain regions which would be more rational and in touch with the present.

The Health Effects of Toxic Stress

Chronic activation of the SNS leads to a multitude of health problems, including:

  • Cardiovascular issues: Chronic stress can contribute to high blood pressure, increased risk of heart disease, and other cardiovascular problems.
  • Weakened immune system: The release of stress hormones can suppress the immune system, making individuals more vulnerable to infections.
  • Mental health conditions: Toxic stress is associated with a higher risk of mental health disorders, including anxiety, depression, Alzheimer’s, and many other mental illnesses.
  • Metabolic changes: Stress-induced cortisol release can lead to weight gain and disturbances in glucose metabolism.
  • Inflammation: Chronic stress and sympathetic system activation can contribute to chronic inflammation, which is linked to a range of health issues.
  • Digestive problems: Stress can exacerbate or contribute to gastrointestinal problems, such as irritable bowel syndrome.

Prevention and Management

When you understand how and why your brain activates the stress response, you can take steps to lessen it to live a calmer life. Basically, anything that helps turn down your brain’s arousal, release stress, and engage your “rest and digest” parasympathetic nervous system (PNS) is going to be of benefit. Some strategies to manage toxic stress include:


One of the best ways to turn down your brain and body’s arousal and prevent damage to your brain from stress is exercise. While you’re probably familiar with the ways exercise helps your brain while you’re doing it with increased oxygen and blood flow, it’s what happens after exercise that really benefits the brain long-term. The protective effects after exercise include:

  • Exercise calms the amygdala raising the fight-or-flight activation threshold.
  • It kickstarts the cellular recovery process by increasing the efficiency of intercellular energy production. This allows neurons to meet fuel demands without increasing toxic oxidative stress.
  • Exercise triggers the production of more receptors for insulin which means better use of blood glucose and stronger cells. It also increases the level of insulin-like growth factor which helps insulin manage glucose levels, and increases synaptic strength, neuroplasticity. and neurogenesis.
  • Exercise increases brain-derived neurotrophic factor (BDNF) production. BDNF acts as a fertilizer to help brain cells function, grow, and make new neurons.
girl doing cardio in gym


Sleep is one of the biggest influencers of your brain health and is a powerful stress reducer. Following a regular sleep routine calms and restores the body, boosts your immune system and hormones, improves concentration, regulates mood, sharpens judgment and decision-making, and lowers cortisol. You can handle stress better when you are well-rested. Not getting enough sleep can make your stress worse.

Social Support Network

Strong relationships with friends and family members can also bolster your mood, improve your outlook, and preserve your mental well-being. Research shows that people with high levels of social support are more resilient in the face of stressful situations. Social support may best help reduce stress by providing the resources we need to thrive, increasing hormones that combat stress and help us feel good, improving overall health, and decreasing the risk of death.


Neurofeedback training can help turn down your SNS stress response by calming the brain’s fear center, the amygdala. Having a less reactive amygdala takes you out of chronic SNS activation fight-or-flight mode, calms your brain and body, reduces stress hormones, and encourages your brain to operate from a baseline state of PNS activation. In this state, your brain and body will be calmer, healthier, happier, and more relaxed.

Mindfulness Practices

One way to activate your PNS is through mindfulness practices, like yoga, visualization, mindful moments, or meditation. Research is showing that mindfulness practices can have significant positive benefits on mental health and health, in general. Practicing mindfulness literally changes your brain and body’s default states to be less anxious and more balanced.

Slow Deep Breathing

Taking slow, deep breaths through your nose into your diaphragm with slow exhales engages the PNS instantly and turns down your body’s SNS stress response. It also allows more carbon dioxide to exit. Slowing down your breath has many benefits for your brain and body. It’s one of the simplest ways to improve your health, both physically and mentally. Relaxed breathing tells your body it’s OK to relax.

A Calmer Brain Means a Calmer You

Our brain advocates at Grey Matters understand your nervous system and how to guide it to be less activated. Our brain training experts can literally retrain your brain to be calmer and less reactive — in a way that alleviates problematic mental and physical symptoms for you.

Neurofeedback successfully improves many conditions, including depression, autism, ADD and ADHD, brain injuries, OCD, stroke recovery, PTSD, addictions, seizure disorders, migraines, chronic pain, IBS and gut issues, and more. By fine-tuning the brain’s performance, neurofeedback can also improve focus and concentration. For example, neurofeedback brain training could enhance a person’s performance at school, golf or other sports, or work.

At Grey Matters, we’re passionate about helping people live their best lives. Give us a call at (317) 215-7208 or send a message today to find out how we can help you.