It was raining again. It's been raining for what feels like most of what we've been calling spring. Dexter — my Bull Shih, which is what you get when you cross a French Bulldog with a Shih Tzu, and yes, we do use the other version of the name occasionally at home, and no, I will not be putting it in the opening paragraph of a professional blog post — was pulling me back toward something he'd missed on the way out.
And I could feel it starting. That thing that happens somewhere around 5pm on a Sunday evening. The invisible hand that reaches into what should be a peaceful hour in the fresh air and starts turning the dial marked "Monday" up, slowly, without asking permission.
The inbox. The messages I'd parked over the weekend — some of which needed a quick yes or no, some of which needed ten minutes of thinking, all of which were sitting there accumulating a kind of quiet gravitational pull. The week ahead, already taking shape in my head while my feet were still technically in Sunday.
Dexter stopped to sniff something. I got annoyed.
And then — because this is what happens when you spend 37 years studying the human body and a reasonable amount of time studying your own — I caught myself. I was watching my HPA axis firing up in real time. Anticipatory stress. The body responding not to a threat that existed, but to a threat that might exist, sometime tomorrow, in a meeting or a message or a cashflow spreadsheet. Cortisol rising for a Monday morning that hadn't happened yet, on a Sunday evening walk with a dog who was just being a dog.
Robert Sapolsky wrote the book on this. Literally. Why Zebras Don't Get Ulcers is one of the most important books on stress biology ever written, and the central observation is elegantly simple: zebras experience acute stress (lion appears, they run, they survive or they don't, the stress response ends) and then they go back to grazing. The HPA axis fires and then resolves. The cortisol spike serves its purpose and clears.
Humans don't do this. Humans manufacture stress from things that haven't happened yet, replay things that already have, catastrophise things that probably won't, and spend Sunday ruining Sunday worrying about Monday. The HPA axis cannot tell the difference between a lion and an inbox. It responds to the thought of Monday morning with the same physiological urgency it would bring to an actual emergency. Not as intensely, but persistently. Chronically. Day after day, week after week, year after year.
"The HPA axis cannot tell the difference between a lion and an inbox. It responds to the thought of Monday morning with the same physiological urgency as an actual emergency. Not as intensely — but persistently. Chronically. Day after day."
What Actually Happens in Your Body
When you perceive a threat — real or anticipated — the hypothalamus releases corticotropin-releasing hormone (CRH). This signals the pituitary to release ACTH. ACTH signals the adrenal glands to produce cortisol. The whole cascade takes minutes. It's exquisitely well-designed for the problem it evolved to solve: short-term physical danger requiring immediate action.
The problem is the resolution. Acute stress — the kind Sapolsky's zebras experience — has a clear end point. The lion is gone. Cortisol drops. The system resets. Parasympathetic tone returns. Digestion resumes. Sleep quality improves. The body goes back to the business of repair, restoration, and maintenance that chronic stress perpetually defers.
Anticipatory stress — the kind humans are uniquely talented at generating — doesn't resolve cleanly. The Monday morning meeting is still there tomorrow. The cashflow concern is still there next week. The background hum of things undone, messages unanswered, decisions deferred — it doesn't switch off when you put your phone down. It runs at a lower level, persistently, keeping cortisol slightly elevated, keeping the sympathetic nervous system slightly engaged, subtly disrupting every system in the body that requires parasympathetic tone to function properly.
Which is most of them. Digestion. Sleep architecture. Immune regulation. Sex hormone production. Thyroid conversion. Gut barrier integrity. The body is not good at running these systems and a stress response simultaneously. It prioritises survival over everything else. Given a chronic low-level signal that survival might be at stake, it deprioritises everything else chronically.
The DUTCH Plus cortisol pattern I see most often in people who describe this kind of chronic background stress is not the dramatic high-cortisol picture of acute HPA axis activation. It is the flattened curve — a blunted cortisol awakening response, a lack of the morning cortisol peak that should provide the physiological momentum to start the day, and a slow, unresolved cortisol that runs a little too long into the evening. The adrenals have been asked to produce cortisol persistently for so long that the system is beginning to adapt — not by resolving, but by blunting.
This is the pattern that explains why people feel simultaneously wired and tired. Why they can't get going in the morning and can't switch off at night. Why the effort required to do normal things feels disproportionate to the task. The system is compensating for a problem it was never designed to run chronically.
The Sunday-to-Monday Shift Is Real
Research on what's sometimes called "anticipatory work stress" consistently demonstrates measurable physiological changes in the days leading up to the working week. Heart rate variability — a sensitive marker of autonomic nervous system balance — declines on Sunday evenings in people with high work stress. Cortisol patterns shift. Sleep quality changes. The body is already preparing for Monday before Monday has arrived.
What makes this particularly interesting — and particularly frustrating for people who care about their health — is that knowing this doesn't automatically fix it. I know the HPA axis biology better than most people. I have written clinical frameworks for managing cortisol dysregulation. I have coached clients through adrenal recovery protocols. And I still felt that cortisol edge creeping in on a Sunday dog walk in the rain.
Because this isn't primarily a knowledge problem. It's a nervous system problem. And the nervous system responds to signals, not to arguments.
What Actually Helps
A long exhale. Genuinely, physiologically, measurably — a slow, extended exhale activates the vagus nerve and shifts autonomic tone toward parasympathetic. The exhale is longer than the inhale. Four counts in, six to eight counts out. Do this five times. Cortisol doesn't evaporate, but the physiological momentum toward it eases. It's not a metaphor. It's vagal tone, and it works.
Gratitude — and I say this as someone who is deeply suspicious of wellness clichés — has a real neurobiological mechanism. The prefrontal cortex, when genuinely engaged, down-regulates amygdala reactivity. You cannot ruminate about Monday and simultaneously be genuinely present to what is actually in front of you. The trick is genuine presence, not performative gratitude. Actually looking at the trees. Actually hearing the birds. Actually noticing the dog — who, it turns out, is not trying to waste your time but is doing the one thing he is perfectly designed to do, which is live completely and only in the present moment.
Dexter, it occurs to me, has solved this. He has never once worried about Monday.
My dad — who is 82, 83 in under four months, has survived what felt like monthly heart attacks for a period, has dementia that is quietly advancing, lost my mum, and lives alone — still gets up every day and gets on with things. He phones me what feels like too much. He repeats himself. He is sometimes mid-sentence when the story stops making sense, or talking about my sister being in the house when she isn't there. He drives me quietly mad with the daily logistics of supporting him.
But here is the thing I know and don't say enough: he is phoning because he is bored and lonely and can pick up the phone any time he wants and he is phoning to speak to his child. His son. And there are times I have not had the time for him — genuinely busy, genuinely pressured — and that is the saddest sentence I know how to write. Because his heart is not right, and it has not been right for years. And one of these times it is going to get him. And he will not be there for that phone call. And I will end up desperately wanting to have it.
He doesn't have the luxury of Sunday dread. He just has today. And he gets up anyway.
The Practical Reality
I am not suggesting you stop working. I am not suggesting Monday is optional. I am saying that the Sunday-to-Monday cortisol shift is not inevitable, it is not healthy, and it is not a fixed feature of modern working life — it is a pattern the nervous system has learned, which means it is a pattern the nervous system can unlearn, with the right signals given consistently over time.
The signals that help: physical movement (the walk itself, if you can actually be on it); slow breathing; genuine sensory engagement with what is in front of you; contact with nature, which has measurable effects on cortisol and autonomic tone; and — critically — a clear, pre-agreed boundary around when work starts on Monday morning, so that Sunday genuinely has an end point.
The signals that don't help: checking messages on Sunday to "get ahead." Mentally rehearsing difficult conversations that haven't happened. Mentally writing emails in your head instead of watching the trees.
I walked Dexter home. He was happy. He'd had a good sniff. The rain had stopped for about four minutes, which felt like a gift. I gave him a cuddle at the door and told him how gorgeous and cuddly he is, which he accepted with characteristic dignity.
Then I came in, made a list of what actually needed to happen tomorrow morning, crossed off everything that didn't, and felt — immediately, measurably, physiologically — better. Not because the work went away. Because the nervous system had been given a signal it could use: there is a plan, the plan is specific, and tonight is not part of it.
Zebras don't get ulcers because they don't ruminate. They don't rehearse tomorrow's threat. They graze, they rest, they respond to what is actually in front of them, and then they return to grazing.
Dexter has been trying to teach me this for years. I'm a slow learner. But I'm getting there.
Want to know what your cortisol is actually doing?
The DUTCH Plus hormone panel maps your diurnal cortisol curve across four time points — showing exactly whether your HPA axis is firing correctly, blunting, or running too long. It's part of the TDG Five-Test Programme.
Learn about the TDG Programme → Take the free symptom quiz