What Chronic Stress Is Actually Doing to Your Brain
By: Brian Hoeflinger, MD
February 22, 2026 | #77
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Disclaimer: Opinions are my own. Not medical advice.
Medical Trivia of the Week
Which part of the brain is most vulnerable to damage from chronic stress? (the correct answer is at the end of this email)
- A) Cerebellum
- B) Hippocampus
- C) Brainstem
- D) Occipital lobe
Stress Isn’t Just in Your Head, It’s in Your Brain
We all know stress feels bad. You know the feeling, racing mind, knotted stomach, trouble sleeping. But most people have no idea that chronic stress is also doing something much more serious: it is physically changing the structure of your brain.
As a neurosurgeon, one thing still surprises people when I tell them: the brain physically changes in response to your life. Scientists call this neuroplasticity. Your brain is not fixed. It grows stronger with the right habits, and it weakens under the wrong ones. And chronic stress is one of the most damaging forces your brain can face.
Here is what is actually happening inside your head when stress becomes a way of life.
The Stress Hormone You Need to Know About
When you encounter a threat, real or perceived, your body releases a hormone called cortisol. This is a good thing in short bursts. Cortisol sharpens your focus, boosts your energy, and helps you respond quickly. It is your body’s built-in alarm system.
The problem is when that alarm never shuts off.
Modern life is full of low-grade, ongoing stressors: work pressure, financial worry, relationship conflict, social media, lack of sleep. These stressors may not feel life-threatening, but your brain and body respond to them the same way they would respond to a physical danger. That means cortisol stays elevated, day after day, week after week.
And that is where the real damage begins.
What Chronic Stress Does to the Brain
It shrinks the hippocampus.
The hippocampus is a small, seahorse-shaped region deep inside your brain. It is your memory and learning center, the part of your brain responsible for forming new memories and helping you navigate the world.
Chronic stress and prolonged cortisol exposure cause the hippocampus to physically shrink. Dendrites, the tiny branches that allow brain cells to communicate, retract and weaken. In some cases, the brain stops producing new cells in this region altogether. Research has shown that people who experience chronic stress can have a noticeably smaller hippocampus over time, which affects memory, learning, and the ability to think clearly.
The good news? Studies also show that when stress is brought under control, some of this damage can reverse. The brain has more capacity for recovery than most people realize.
It overactivates the amygdala.
The amygdala is your brain’s threat detection center. Under normal conditions, it works together with your prefrontal cortex (the rational, thinking part of your brain) to assess whether something is truly dangerous.
Chronic stress throws this balance off. The amygdala becomes hyperactive, scanning constantly for danger and triggering anxiety, irritability, and fear responses even when no real threat exists. At the same time, the prefrontal cortex, which is supposed to be the brakes on these reactions, gets weakened. The result is a brain that is stuck in alarm mode, making it harder to think rationally, stay calm, or feel in control.
It weakens the prefrontal cortex.
Your prefrontal cortex is what makes you human. It handles decision-making, impulse control, planning, and emotional regulation. It is the part of your brain that says, “wait, let me think about this before I react.”
Chronic stress reduces the connectivity of this region and makes it less effective over time. People under prolonged stress often notice they are more impulsive, more reactive, and have a harder time concentrating or making good decisions. That is not a personality flaw, it is what stress does to the brain.
Long-Term Risk You Can't Ignore
What is most concerning about chronic stress is not just how it affects you today. It is the long-term risk.
Elevated cortisol over many years has been linked to accelerated cognitive decline and increased vulnerability to conditions like Alzheimer’s disease. The hippocampal damage I described earlier is the same kind of structural change we see in the early stages of dementia. Stress does not just make you tired and anxious, it may be quietly accelerating the aging of your brain.
This is not meant to just scare or alarm you. It is meant to motivate you. Because unlike many risk factors, chronic stress is something you can actually do something about.
What You Can Do About It
The research is clear: interventions that reduce stress also protect the brain. Here is what has the strongest evidence:
Exercise regularly. Even moderate physical activity, such as 30 minutes of daily walking, lowers cortisol, promotes new brain cell growth in the hippocampus, and strengthens the prefrontal cortex. Exercise is probably the single most powerful tool we have for brain protection.
Prioritize sleep. Poor sleep raises cortisol and compounds every negative effect of stress on the brain. Getting 7 to 9 hours of quality sleep each night is not a luxury, it is essential maintenance for your brain.
Practice some form of daily stress reduction. This does not have to be complicated. Five to ten minutes of deep breathing, meditation, prayer, journaling, or even a quiet walk outside (without your phone!) can meaningfully lower your stress response over time. The key is consistency, not perfection.
Protect your social connections. Strong relationships buffer the effects of stress on the brain. Regular time with people you care about is not just good for your mood, it is genuinely protective for your long-term brain health.
Limit what you can control. You cannot eliminate all stress from your life. But you can reduce unnecessary exposure. Limit negative news consumption, reduce social media scrolling, and be intentional about where your time and attention go.
Stress is real, and it is powerful. But so is your ability to respond to it. The brain you have today is not fixed. It is constantly changing in response to your habits, your choices, and your lifestyle. That is both a warning and an opportunity.
Take care of your brain. It is the only one you have.
Impactful Quote of the Week
"Nothing is permanent in this wicked world, not even our troubles."
- Charlie Chaplin
All my best,
Brian Hoeflinger
P.S. - if you enjoyed this newsletter, you may enjoy my book that details my life as a neurosurgeon and the loss of my oldest son, Brian (see below a synopsis) and/or my podcast where I explain topics in further detail.
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Check out My Book
Life and Death . . . Two words with such opposite meaning and which inflict such contradictory emotions and yet are so closely intertwined in our lives. As parents, we bring meaning and life into this world through our children. Our lives become defined as a result. We learn the joy, hardship, and responsibility of shaping an innocent life. But a day will come when that life will be taken. For some, death will come too soon. This is the story of my son, Brian Nicholas Hoeflinger, who died unexpectedly at age 18.
https://doctorhoeflinger.com/products/the-night-he-died-the-harsh-reality-of-teenage-drinking
Check out My Podcast
The Dr. Hoeflinger Podcast is about more than medicine, it’s about living a fuller, healthier, and more meaningful life. My son, Kevin, and I discuss medicine, health, fitness, lessons learned from personal tragedy, family, and purpose. Along the way, we invite inspiring guests to bring fresh insights and perspectives. Watch or listen to the podcast below.
YouTube: Click here
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Medical Trivia Answer:
The correct answer is B) Hippocampus
*Disclaimer: This newsletter and blog is for general informational purposes only and does not constitute the practice of medicine, nursing, or other professional health care services, including the giving of medical advice, and no doctor/patient relationship is formed. The use of information on this newsletter and blog or materials linked from this newsletter and blog is at the user’s own risk. The content of this newsletter and blog is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Users should not disregard or delay seeking medical advice for any medical condition they may have and should consult their healthcare professionals for any such conditions.
