How stress shows up in the body

The jaw that aches on waking. The stomach that has opinions about Sunday evenings. The shoulders that have been up near the ears since March. The chest tightness at the top of a difficult week, the eczema that returns with the deadline, the cold that arrives on the first day of the holiday.

Somebody will eventually say it is probably just stress, and the word doing the damage in that sentence is just. It lands as a dismissal — nothing is really wrong, you are producing this. It should land as a mechanism, because what is actually being described is a chain of physiology with names at every link, and those links do real things to real tissue.

The stance here: the symptoms are not imaginary, and that is precisely why "it is stress" has to be a conclusion you arrive at after the alternatives have been checked, not a way of avoiding checking them.

Robert Sapolsky's framing remains the clearest. The stress response is an emergency system built for a short, physical crisis: mobilise glucose, raise blood pressure, sharpen attention, and postpone everything that can wait — digestion, repair, reproduction, parts of immune function. Over minutes it is superb. It was never designed to run for a fiscal year.

Two pathways do most of the work. The fast one is sympathetic: adrenaline, within seconds, giving you the heart and the hands. The slow one is the HPA axis — hypothalamus to pituitary to adrenal — which releases cortisol over minutes to hours and keeps it available for as long as the signal continues. Chrousos' review of the stress system is the standard account of what happens when that signal does not stop.

Bruce McEwen's term for the accumulated cost is allostatic load: the price of maintaining stability through repeated or sustained adjustment. Not one system failing, but many systems held slightly off their set points for long enough that the holding itself becomes the problem. That is the physiological content of a difficult year.

What it produces, plausibly and mechanistically:

• Muscle. Sustained low-grade tension in jaw, neck, shoulders and lower back. Tension-type headache. Teeth-grinding at night.
• Gut. Digestion is one of the first things postponed. Altered motility, cramping, and a well-documented worsening of irritable bowel symptoms under stress.
• Sleep. Cortisol has a daily rhythm and is meant to be low at night. Chronic activation interferes with it, which is most of what the tired but wired state is made of.
• Immune. Short stress mobilises immune function; prolonged stress suppresses parts of it. Slower wound healing and more frequent minor infections are the reliable findings.
• Cardiovascular. Raised blood pressure over long periods, with the associated risk that carries.
• Skin. Flares in eczema and psoriasis are among the most consistently reported stress associations.

There is a second half, and leaving it out makes this page less useful.

Symptoms are not transmitted from the body to awareness like a meter reading. As the entry on interoception sets out, the brain is predicting the body's state and adjusting. Van den Bergh and colleagues call the step from bodily signal to experienced symptom an inferential leap — the brain is deciding what the signal means, using expectation, attention and context.

This explains things that a pure tissue account cannot. Why attention makes a symptom stronger. Why a symptom you have been warned about is more likely to appear. Why symptoms cluster with worry about symptoms. And why two people with the same measured physiology report very different amounts of suffering.

Two cautions come with it, in both directions. The leap does not make the symptom fake — the pain is the pain regardless of which part of the chain produced it. And the leap is not a licence to stop looking: "the brain is predicting it" is a hypothesis about a symptom, not a diagnosis of one.

This is the part we want to be unambiguous about, because pages like this one are read by people deciding whether to bother anyone.

Go and be examined. Chest pain, breathlessness, palpitations, unexplained weight loss, persistent abdominal pain, a change in bowel habit, a new severe headache, numbness or weakness, and anything that wakes you from sleep get assessed medically. Thyroid disease, anaemia, coeliac disease, diabetes and sleep apnoea all present as "stress" and all are found with ordinary tests. A stress explanation for a symptom nobody has examined is a guess wearing a lab coat.

Being told the tests are normal is information, not a dismissal. Henningsen and colleagues' work on bodily distress is clear that the best outcomes come from taking both halves seriously at once — investigating properly, and then treating the distress as real rather than leaving the person with nothing but a negative result. A normal scan does not mean nothing is happening. It means the thing happening is not the thing that scan looks for.

And this page is not a diagnosis of anything. It is background for a conversation, and it is a better conversation when you can say what has been happening and for how long.

Treat the pattern as data about your life, not about your character. The body is often the first honest reporter in the system — it registers the job, the situation or the relationship that everybody has agreed to describe as fine. The question worth asking of a symptom that has a schedule is not what is wrong with me, it is what does it track.

Know your own signature. People are consistent: for one person it is always the gut, for another the jaw, for a third the sleep. Knowing yours gives you a week or two of warning before things get expensive, which is the entire practical value of knowing it. The Stress Response test reads which way your system tends to go under load, and the entry on fight, flight, freeze and fawn describes those four settings in the moment.

Interrupt the physiology, not just the thinking. Because the fast pathway is bodily, the reliable interventions are bodily: slow exhalations, which pull on the parasympathetic side directly; movement, which completes the response the body was prepared for; and sleep, which is where the repair postponed by the stress response is meant to happen — sleep debt is the other half of the loop.

And watch for the point where it stops being stress and starts being exhaustion. If the symptoms have stopped tracking events, if the recovery no longer happens on holidays, and if the flatness is now the baseline rather than the bad weeks, that is the territory of burnout and emotional exhaustion, which do not resolve on their own.