Why Zebras Don't Get Ulcers — and Why You Probably Do
There's a book I find myself recommending often, written by a Stanford neuroscientist and primatologist named Robert Sapolsky.
It's called Why Zebras Don't Get Ulcers. The title sounds almost like a joke, but the question underneath it is deeply serious. Why do humans suffer so much more from chronic stress-related illness than other animals?
Sapolsky's answer changed how I think about stress, and about the work I do with clients. I want to share some of his thinking here, because it lands a particular kind of clarity on what so many of the people I see are actually living through, and on what it might take to live differently.
The Zebra and the Lion
Picture a zebra on the African savanna. A lion appears. The zebra runs.
Its body does what bodies are designed to do. Heart pounding, muscles firing, blood diverted to the limbs that need to move, digestion temporarily suspended, immune function paused, reproduction shelved. Every system gets recruited toward the single goal of survive this next sixty seconds.
If the zebra survives, and most do, what happens next is what matters. Within minutes, sometimes within seconds of being out of immediate danger, the zebra's body returns to baseline. The heart slows. The breath settles. Digestion resumes. The whole emergency apparatus stands down.
The zebra goes back to grazing.
It does not lie awake that night replaying the chase. It does not develop chronic anxiety about lions. It does not lose its hair from the worry. It does not, as Sapolsky's title gestures toward, get ulcers.
The stress response, in a zebra, does exactly what it evolved to do. It activates in the presence of acute threat, mobilizes resources for survival, and shuts off when the threat passes.
Then there is us.
The Problem of the Human Mind
Sapolsky's central insight is that humans have invented something other animals largely don't have: the capacity to generate the same physiological stress response without any actual present threat.
We can sit in a chair, in a safe building, in a country with no lions, and produce the full cascade of fight-or-flight chemistry, meaning cortisol, adrenaline, elevated heart rate, suspended digestion, immune suppression, all of it, by thinking.
We worry about a meeting tomorrow. We replay a conversation from two weeks ago. We imagine a future in which we lose our job, our home, our health, our partner, our standing, our peace. We rehearse arguments that may never happen. We grieve losses that haven't occurred yet. We brace for outcomes that exist nowhere except in our minds.
And our bodies, which evolved to respond to threats with action, respond to all of it as if it were the lion.
The zebra has no language for next month's deadline. The hippopotamus does not lie awake worrying about retirement. The savanna baboon never composes the email he wishes he hadn't sent. We are smart enough and verbal enough to generate the conditions for chronic stress through pure thought.
That is a uniquely human achievement. It is also slowly making us sick.
What Chronic Stress Actually Does
Sapolsky spends much of the book documenting what happens when the stress response stays on too long.
Heart disease. High blood pressure. Damaged blood vessels. Suppressed immune function. Disrupted sleep. Reproductive problems. Memory and cognitive impairment. Increased vulnerability to depression and anxiety. Greater susceptibility to addiction. Damage to the hippocampus, a part of the brain involved in memory and emotional regulation. Even some forms of accelerated aging.
The list is long, and it's sobering. The stress response itself, the same chemistry that lets a zebra outrun a lion, is corrosive when it doesn't shut off. The body wasn't built to live under emergency conditions for years on end. It was built to use emergency conditions briefly, then return to baseline.
Most of the chronic illness Western medicine treats today, Sapolsky argues, is downstream of this single mismatch: a stress system designed for episodic crisis, running continuously in a species that has invented a continuous source of psychological threat.
If you want the mechanics of how that system actually works, from amygdala to HPA axis to the parasympathetic brake that's supposed to switch it off, I've laid that out separately in why your body won't stop bracing.
Why This Hits High Achievers Especially Hard
What I find most useful about Sapolsky's framing, and what often lands hardest for the clients I work with, is what it reveals about a particular kind of suffering that's hard to name from the inside.
Many of the people I see are not in crisis, exactly. Their lives are objectively going well. They have careers that work. Families they love. Resources, options, security.
And their bodies are running as if they were being chased.
They wake at four a.m. with a heart already pounding. They notice they haven't taken a full breath all day. Their digestion is off. Their sleep is fractured. Their patience is thin in a way that doesn't match the actual stakes of their actual life.
Sapolsky's framework helps explain something that's easy to misunderstand. The body isn't reacting to the present. It's reacting to the constant low-level threat the mind is generating on a hundred different fronts: the meeting, the parent, the kid, the news, the relationship, the vague sense of falling behind, the inner critic, the future. Each of these is a small lion. Each fires the same ancient system. None of it ever resolves cleanly. The system never gets to stand down.
This isn't weakness. It isn't bad coping. It's a body running its evolutionary programming in conditions that programming wasn't designed for. The wonder isn't that so many people have ulcers, anxiety, sleep problems, or chronic exhaustion. The wonder is that any of us are okay at all.
What Sapolsky Suggests Helps
Sapolsky is a scientist, not a self-help author, but the last sections of the book do offer some insight into what actually helps. They're worth taking seriously, partly because they're grounded in the science he spends the rest of the book laying out.
A few of his most useful points:
Predictability and control matter enormously. Stress is far more damaging when we feel we have no control over what's happening to us, and when we can't predict what's coming. Even the illusion of control reduces stress. This is part of why so many people respond well to small, manageable practices they get to choose for themselves, and why being micromanaged or living in chronic uncertainty is so corrosive.
Outlets matter. Some way of discharging the activation, whether that's physical movement, expressive activity, hobbies, or creative work, gives the body somewhere to put the energy the stress response generates. Sapolsky is quick to note that outlets only help if they don't harm someone else. Venting at a person who didn't earn it just relocates the ulcer.
Social connection is protective at a biological level. Real social support, not just being around people but being known and held by them, measurably buffers the stress response. People with strong relational bonds have better cardiovascular health, better immune function, and better outcomes across the board.
Perspective matters. The same external event can land very differently depending on the meaning we make of it. Stress responses are partly modifiable by how we frame what's happening, though Sapolsky is honest that this is harder than self-help books often suggest. A practice like the Triangle of Awareness is one concrete way in, because it works on noticing the frame rather than arguing with it.
What His Framing Doesn't Quite Capture
Sapolsky's book is brilliant on the biology and the behavior. What it doesn't go as deeply into, because that wasn't his project, is what therapy reveals. For many people, chronic stress isn't just a response to current life. It's also the lingering signature of older experiences.
Trauma, early relational dynamics, formative experiences in childhood: all of these shape the threshold at which your stress response fires. People with histories of chronic uncertainty in childhood tend to have nervous systems that stay vigilant even in stable adulthood. People who grew up needing to manage other people's emotions tend to scan for threat in every relationship. People whose bodies experienced things they couldn't process at the time often carry that material somatically, where it continues to fire the alarm long after the original event is over. Sometimes the anxiety isn't really about now at all.
This is the part I think is most important to add to Sapolsky's frame. Chronic stress in adulthood is often layered. There's the genuine stress of current life, meaning real work, real responsibilities, real challenges. And there's also the older material running quietly underneath, shaping how your nervous system interprets every present-day situation.
You can do all the right current life interventions, including exercise, sleep, social support, and mindfulness, and still find yourself unable to settle, because the deeper layer hasn't been touched. It's also why understanding the mechanism doesn't calm the system. Reading this post will not lower your cortisol.
This is part of where therapy comes in. Not as a replacement for the practical changes, but as the work that addresses what the practical changes can't reach on their own.
What I Take From This
Sapolsky's book has stayed with me for a few reasons.
It honors the body. It takes seriously that chronic stress isn't a character flaw or a thinking problem. It's a physiological state with real consequences, and reversing it requires more than telling yourself to relax. It's part of why, in my experience, healing has to reach the body.
It honors the strangeness of being human. We are the only species that can suffer from imagined futures and remembered pasts, and that capacity comes with both gift and cost. The same minds that build civilizations, write poetry, and love deeply also generate the chronic background hum that makes us sick.
And it points toward what real intervention might look like. Not just stress management in the small-fix sense, but a deeper relationship with the body that's been carrying all of this, and with the older patterns that may be feeding the activation underneath.
For the people I work with, this often involves several layers of work at once. Real changes in daily life. Practices that engage the nervous system directly. Therapy that addresses the older material still firing in the present. Sometimes body-based tools like the Shiftwave chair or BrainTap, which can help a system experience regulation it has forgotten is possible.
None of this is fast. The patterns of chronic stress took years to develop, and they take time to soften. But softening is genuinely possible. The same body that learned to brace can also learn to settle. The same nervous system that's been on high alert can also relearn rest.
It's not the same as becoming a zebra. The capacity to generate stress through thought is part of what makes us human. But we can, slowly and with the right support, develop a different relationship to that capacity, so it serves us instead of slowly making us sick.
A Last Thought
If your body has been running on emergency settings for years, and you've been wondering whether something is wrong with you, Sapolsky's book offers a quietly useful reframe. Nothing is wrong with you. You have a body running its evolutionary programming in a world that's generating more threat signals than the system was ever designed to metabolize.
The path back isn't to override the system or to muscle your way to calm. It's to slowly help your body learn that the lion isn't actually here. That requires more than information. It requires lived, repeated experiences of safety, in your body, in your relationships, in the places you can find rest.
If you'd like a place to do that work, I'd be glad to hear from you. You can book a free consultation here.