How Chronic Stress Rewires Your Brain

Last Updated July 2, 2025

Many researchers and doctors would agree that stress can be as dangerous to the brain as drugs, and nobody is immune. We already know that stress over time makes you vulnerable to a number of adverse health conditions, but what about its impact on the brain in particular?

Until relatively recently, we thought that once a brain cell died, that was it — you were born with all of the brain cells you would ever have. Today, however, we know that isn’t the case. That was before we discovered neurogenesis (the formation of new brain cells) and neuroplasticity (the adaptive power of the brain). Our brains continue to grow and change over time, often in response to stressors.

Modern life presents a whole new challenge to the stress management systems of the brain, but there are ways to overcome negative effects of stress.

What is Stress? Understanding the Body’s Response

While we often consider stress a negative sensation, stress itself is neutral: “your body’s response to anything that requires attention or action.”  In other words, it’s how we respond to a stressor that determines its real flavor. Consider the feelings of excitement versus anxiety. One has a positive connotation, the other negative, but overall, they feel very similar. They are two sides of the same coin.

Most of the time, our bodies understand how to respond to a stimulus.  In the interest of efficiency, the brain automates almost everything that it can. If you perform the same activities the same way every day, you probably don’t need to think about it much. That’s why you can get all the way home from work without any actual memory of the drive — your brain is essentially on autopilot.

The brain switches to a more active mode when it experiences something new and different. That’s when its problem solver, your cerebral cortex, gets involved. For example, if while you were on that drive home, a deer ran across the road in front of your car. Since that’s not “normal,” your brain immediately alerts your cortex, which instantly tells your foot to slam on the brakes.

It should be noted that not everything unusual is going to cause stress. Dropping your keys on the way out of the door might get your attention, but it doesn’t necessarily cause stress. According to Lazarus and Folkman, a stressful situation is one in which the demands on you exceed your current available resources. Stress occurs when you’re pushed past your limit, and you literally cannot handle more.

Luckily, the body has a response for that.

How the Human Brain Evolved to Handle Stress

Because stress is completely natural and expected, our bodies and brains have evolved accordingly to deal with threats.

For our hunter-gatherer ancestors, stress might have meant an immediate threat to their survival, like stepping on a poisonous snake. Their brains would have kicked the body into high gear to meet that threat.

Upon encountering a stressor, this ancient human’s brain would have immediately engaged the adrenal and autonomic nervous systems, which release adrenaline and cortisol into the bloodstream, which quickly floods the body and prepares it to do what it needs to do to survive.

Specifically, here’s how the brain and body respond:

• Increased heartbeat and respiration. You breathe quickly and shallowly into your lungs and the heart pounds, helping to oxygenate your blood and quickly supplying vital organs with nutrients.
• Increased energy. Your liver starts pumping glucose out to the bloodstream, instantaneously providing you with enough physical energy to do what’s needed.
• Systems prioritized. The brain coordinates a response that diverts the most energy and resources to the areas that need it, like your muscles. It also and tones down activity in less-than-essential systems, such as your digestive system.
• Tunnel-vision. Your pupils dilate, allowing more light in; this serves to improve your central vision, which is presumably focused on the current threat. Hearing and peripheral vision actually worsen in an effort to focus attention on the central threat.

You may have heard this referred to as the “fight or flight” response. It means that we’re highly adapted to deal with acute stress because stress management is wired into our DNA. Ostensibly, that’s a very good thing: We’re stil here, so it seems it worked out for our ancestors fairly well.

When Stress Overloads the Brain’s Natural Defenses

While our brains haven’t changed much in the last 40-50 thousand years (a blink of the eye in terms of evolution), our lifestyles have changed drastically. Threats from wild animals have become threats of deadlines, traffic, bills, family conflict, and more. These modern stresses aren’t actually going to eat you alive, but your brain doesn’t necessarily understand that.

And so we’re faced with stressors almost constantly. While we’re wired well for acute stress, our brains haven’t caught up to cope with the onslaught of our present-day mental attacks.

Chronic Stress and the Breakdown of Brain Regulation

Stress management is mostly about how well you’re able to regulate your nervous system. The autonomic nervous system, the one that controls all of your involuntary functions, has two components. The sympathetic nervous system is designed solely for the fight-or-flight response mentioned above. It engages whenever a threat, real or perceived, is presented.

But you also have a parasympathetic nervous system, which is often called the “rest and digest” system. As you might guess, this system takes over when we’re not under stress. Its main job is to undo all of the changes the body undergoes when responding to stress; in other words, it helps you calm back down and “reset.”

The mismatch between our genetics and our environment means our alarm systems don’t work as intended. If the alarm system stays on all the time, or if something repeatedly triggers it, the end result is chronic stress.

How Long-Term Stress Impacts Brain Health

Stress and trauma are well known by now as contributing to a number of serious health conditions, including heart disease, stroke, and cancer. But how specifically does stress affect the brain?

Stress and Brain Rewiring in Mental Health Conditions

This probably isn’t surprising: Chronic stress can lead to mental health concerns. Doctors and researchers know, for example, that patients with PTSD have a pathological imbalance of grey and white matter in the brain. Researchers at UC Berkeley showed that chronic stress leads to a similar imbalance by creating more white matter that may lead to communication disruptions in the brain.

The study also showed how the brain may be literally rewired in some mental health conditions. Stronger neuronal and communication pathways between the hippocampus and the amygdala, for example, may lead to a quicker and stronger fear response. Conversely, less connectivity to the prefrontal cortex, where logical thinking and decision-making occur, can mean your emotional brain becomes the “louder” voice in your head that drowns out the thinking brain.

Can Stress Kill Brain Cells? What the Science Says

As mentioned before, neurogenesis, or the formation of new brain cells, can occur in the hippocampus, responsible in part for mood, memory, and learning. Chronic stress has been shown to slow down or impair that neurogenesis. A recent study also confirmed that even acute stress affected not the formation of, but the survival of new neurons in the hippocampus.

How Stress Affects Memory and Learning

Think that getting older is having an effect on your memory? More than likely, it’s related to stress, not just age. Research has shown that even acute stress can affect your memory. Stress appears to affect both the formation of new memories, as well as the retrieval of previously formed ones.

Interestingly, stress even appeared to affect your cognitive flexibility. Under stress, you’re less likely to “update” your memories or knowledge in light of new information, meaning stress could make you stubbornly stick to errant information.

3 Ways to Reset Your Stress Response and Protect the Brain

Stress is a fact of life. You can’t change it, but you can change how you react to stress. Here are three ways you can practice training your body to reset its stress response:

• • • Step 1: Recognize the Signs of Stress in the Moment
      

  The first, and often hardest part of dealing with stress is simply recognizing that it’s there. Often, we unconsciously (or consciously) run from stress before we even have a chance to deal with it, often in less than healthy ways. But instead of running away or avoiding it, what about just looking at it? By stopping and just recognizing “oh, this is stressful” can go a long way towards diffusing the situation.

  • • Step 2: Notice How Stress Shows Up in the Body
      

  When we feel stress, we often carry it in our bodies. If you could do a mental inventory the moment you’re under stress, you’re likely to notice tense, raised shoulders, a tight belly and jaw, or various aches and pains. Everyone is different, and stress presents differently for each of us. But paying attention to where you actually physically feel stress in the body can help release it.

  • • Step 3: Shift Your Mindset Toward Resilience

  Remember that stress is really neutral. It’s up to you to decide how you choose to deal with it. Modupe Akinola of Columbia Business School talks about a “contracted” stress response versus a “flow state” response. A contracted response would be to pull back, avoid, and withdraw. A more open state is like that of athletes or musicians during a game or performance. Both are heightened states of arousal and attention, but with different attitudes held towards them.

Yes, Stress Changes the Brain — But So Can You

Both acute and chronic stress can affect the brain as well as the body. Even though we know now that brain cells can be restored, it’s important to learn to deal with the ever-present stress that inevitably affects our lives. By learning to respond more positively to stress, we can help the body and brain recover and heal.

Keep going! Learn about cortisol (the stress hormone), stress management, and how the connection between nutrition and stress.