Robert Sapolsky
Built for escape, left switched on
The problem is that it won't turn off
Why Zebras Don't Get Ulcers
People and zebras run the same stress system. Why only one of them gets sick from it.
What actually happened?
The title is the whole argument. Zebras don't get ulcers because their stress response runs for a few minutes. A lion charges: heart rate up, glucose released, immune function paused — and the moment they've escaped, it shuts off. Ours is identical, and we run it against mortgages, managers and an unanswered email. So Sapolsky's verdict is that what makes people ill isn't the stress, it's the response staying on. Its price is suspended repair, digestion and long-term building. Fine briefly. Left on, it diverts the maintenance budget indefinitely.
It isn't intensity, it's duration
A week-long sprint doesn't damage anyone. Two years of being permanently on call does. To assess your own state, the question isn't how tired you've been lately. It's when the system was last genuinely switched off.
One project straight into the next for two years. The body never entered repair mode, which is more dangerous than any single hard week.
The cost is charged somewhere you can't see
What gets paused under stress is immunity, digestion and tissue repair, and those debts don't show up the same day. So people misjudge how well they're coping. By the time symptoms appear the account has usually been running a long while.
Rarely ill through a punishing stretch and flattened the moment the holiday starts. Relaxing didn't weaken you.
The specifically human problem is imagination
A zebra starts the response on seeing an actual lion. A person can start the entire thing by thinking about something that might happen. That's the core mechanism of chronic human stress, and why working on the thoughts themselves is a real intervention.
Rehearsing the worst version of a conversation that hasn't happened produces much the same physiology as having it.
How do I use it today?
Where you are: tense for a long time, unable to point at what's wrong.
Ask first: when did this system last actually switch off? Has there been any stretch where I wasn't on call?
Where it goes wrong: hearing it as 'stress is all in your head' — real pressure has real physiological consequences. This is about duration, not whether it's genuine.
Lines to keep
Zebras don't get ulcers because the response runs for minutes.
What makes people ill is the response that won't switch off.
A person can start the whole thing by imagining it.