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Why Does Stress Make Us Ill? · So That's Why

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Jen: Welcome to the So That's Why podcast, where we unpack the
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science behind everyday questions.
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I'm Jen.
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Jamie: I'm Chris.
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And I'm Jamie.
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Jen: Right, here's something that sounds completely back to
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front when you first hear it.
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Stress on its own isn't what makes us ill.
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So a little bit of stress is genuinely good for you.
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I know I need a bit of stress sometimes to help me complete those deadlines.
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But- Why can stress make us ill?
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Because a system that's brilliant in short bursts becomes a problem
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when it never gets switched off.
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Jamie: That's mildly irritating to hear, if I'm honest.
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I spent years blaming stress for everything, bad mood, lost keys, the lot.
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Now you're telling me it was on my side the whole time?
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Jen: Yeah.
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Well- But I think I'll carry on blaming it.
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Chris: Yeah.
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It's on your side in the right dose, I think, I think it's fair to say.
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So if it's the nerves before a big presentation that sharpen you up, or,
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you know, the push before a deadline that gets you focused, those types
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of stress can be really helpful.
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And in fact, there's even a name for it.
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It's called
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Jen: eustress.
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Which I am definitely gonna use that phrase in an argument.
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I'm not stressed, I'm eustressed.
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Of
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Chris: course, the trouble is, um, like most of us aren't living in these kind of
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short bursts of stress anymore, are we?
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It's kind of chronic stress normally.
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Jen: Yeah.
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Jamie: So how big is the problem?
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Jen: Okay.
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Well, we love our facts on this podcast, don't we- … and our research.
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So there was a survey of more than 145,000 adults in 144 countries, and they found
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that 37% had felt significant stress the day before they did the survey,
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and 39% experienced serious worry.
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And every one of those measures, stress, worry, sadness, is
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higher than a decade ago.
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Jamie: More than one in three people on an ordinary day, not a
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crisis week, just an ordinary day.
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Chris: I know.
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Jen: I've got to say- I know.
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It's huge.
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Yeah.
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It's really… It's sad, isn't it?
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Chris: Yeah.
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You did well to remember all those, uh, stats in one go as well.
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I mean, totally got them the wrong way around.
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Um, but the thing is, those stats, they add up, don't they?
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They stack up because the World Health Organization now counts
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over a billion people as living with a mental health condition.
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Um, so rates anxiety and depression, which are both tangled up with
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stress, as the second-biggest cause of long-term disability worldwide.
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Jen: That's huge, isn't it?
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Yeah.
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Absolutely huge.
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And, you know, the picture in the UK is just as stark,
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so some more figures for you.
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Across '24 and 2025, 964,000 workers were dealing with work-related
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stress, anxiety, or depression.
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And here's what is interesting.
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The year before, it was 776,000, so that's the sharpest single-year jump
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on record, and it actually costs the economy around 22 million working days.
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Matt: Wow.
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Jamie: 964,000 people.
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That's a city worth of workers signed off.
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And the real-life figure's probably higher because plenty of people
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just, just push through it.
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Jen: Yeah.
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I think that's a really helpful comparison, that it's a city worth.
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It gives people a bit of a-
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Chris: No, definitely,
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Jen: yeah … a picture, isn't it?
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Chris: Yeah.
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And you're right, Jamie, it's almost certainly gonna be higher, isn't it?
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For, for sure.
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Um, so around 80% of UK workers say they feel stressed regularly, which
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is no surprise, and statistics suggest that stress-related absences from
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work are up by over a third since 2020
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Jen: I think, I'll be honest, my first instinct reading those was to feel
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stressed about how stressed everyone is, which obviously helps nobody.
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Chris: Absolutely.
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And that's exactly why understanding the mechanism matters more than anything else.
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So shall we get into what's actually happening in the body?
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Jamie: Please do, because to me, stress has always been
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just a sort of vague concept.
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So what exactly is happening in your body when you're stressed?
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Chris: So when the brain decides there's a threat, whether it's, um, real or
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imagined, it fires up two systems.
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So the first is a fast one that floods your, well, floods you with adrenaline,
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so your heart rate speeds up, your blood pressure rises, and sugar pours into the
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blood to get energy to your muscles fast.
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Jen: Yeah, which obviously sounds like a good system.
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Your body needs that.
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But then after that, a slower one follows, and that releases cortisol,
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which is the main stress hormone.
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We've chatted about it in different episodes.
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So cortisol keeps your energy topped up, and to do it, it quietly turns
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down anything you don't need in an emergency, like digestion, repair, and
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even a chunk of your immune system.
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Jamie: So if you were to picture it like a kitchen, you get a text that guests
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are arriving at the door in five minutes.
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Mm. Everything urgent gets done immediately.
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The gas goes on, the hob's on full.
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That's the adrenaline, the heart racing, energy flooding your
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body to deal with the threat.
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And everything that can be is dropped, the washing up, the post
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on the mat, the laying the, putting flowers in vases on the table.
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That's your digestion and your immune system being put on hold.
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All the effort goes into the emergency, none to the upkeep.
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Jen: Yeah.
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Chris: That's a very passionate analogy.
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I'm, I'm assuming you've had some kind of house party
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recently- I just love my cooking
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… Jen: that got you quite stressed about it.
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I love the flowers on the vase as
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Chris: well.
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I know, definitely.
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Um, but the thing is, when it comes to these kind of short scrambles of, of
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stress, your body really is brilliant at coping with that short scramble.
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So back to Jamie's analogy, the hope is that the guests
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actually leave at some point.
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So once you've kicked everybody out and done the washing up, you can
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have a little sit down and a relax.
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The heart rate settles, digestion comes back to normal, and everything resets.
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Jen: But coming back to stress, the problem is the version where the guests
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never leave, so the hobs stay on full day after day, and that upkeep never happens.
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The post piles up, the washing up festers, and the kitchen, after
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a while it starts to fall apart.
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Chris: Is this Jamie's house party again?
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The flowers
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Jen: are dead in the vase.
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Well, potentially.
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I don't, I don't know.
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Chris: I want to went to the… I want to get an invite to the next one.
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Jen: But that's, that's like chronic stress, and your body's
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stuck in that emergency mode with no time to actually repair itself.
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Jamie: And you're telling me that's what does the damage?
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Not the scramble, but the scramble that never ends.
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Mm. Anyone can run a five-minute panic.
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Nobody's built to run it for a long time.
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Chris: Yeah, and that's it in one line.
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So in short bursts, this saves you, but if you run permanently, the same
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chemistry that helped you starts wearing the body down system by system.
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Jen: And the heart shows it the most clearly.
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So chronic stress is now, uh, treated as an independent risk factor for
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cardiovascular disease, and it's ranked alongside high blood pressure,
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high cholesterol, and smoking.
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I think that's fascinating.
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Wow.
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Jamie: Hang on.
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So you're putting long-term stress into the same bracket as smoking?
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Jen: Yeah.
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And- The effect on the body
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… Chris: I know.
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And it, I mean, it sounds dramatic, but there is actually method
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to the madness, isn't there?
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So, um, adrenaline and cortisol keep your heart rate and your blood pressure
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up, but over time, that damages blood vessels and builds plaque in the arteries.
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And in fact, there was, um, there was a 2023 study that found that depression and
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anxiety, which sit right next to chronic stress, they raised the risk of a major
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heart event by about 35% and brought the warning signs forward by about six months
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Jen: It's huge.
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And people with the highest cumulative stress scores, they showed roughly a
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22% higher risk of that arterial plaque and a 20% higher risk of cardiovascular
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disease independent of the usual suspects.
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Jamie: So although stress doesn't hand you a heart attack on
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the spot, it quietly moves the whole- Yeah … timeline forward.
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Chris: Yeah.
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Absolutely.
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And that's the shift that matters.
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So if you've already, if you already know you've got kinda hearth- heart
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risk factors, it's a reason to have a kind of sensible conversation with your
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GP, but it's not a reason to panic.
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Jamie: Yeah.
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So be wary of it if you're in the high risk category, but carry on calmly.
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Chris: Absolutely right.
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Yeah.
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And, um, in terms of the immune system, so the immune system's
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response to stress can be useful, but it can also be counterintuitive,
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and it depends on the timeframe.
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So in the short term, as we mentioned earlier, a burst of stress actually
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sharpens your defenses and your body braces for a possible injury.
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Jamie: So the five-minute stress version is the immune
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system rolling up its sleeves.
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Mm-hmm.
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Jen: For a few minutes, yes.
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But run it for months and it flips.
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So sustained cortisol, that suppresses parts of your immune response, so it
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slows your T-cells, and there's ev- even evidence it blunts how well vaccines work.
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Mm.
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Jamie: That's the cruel timing everyone knows.
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You're never ill during a busy stretch, and then as, as soon as the holidays
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come along, you get ill the first day.
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Jen: Oh, that's happened to me so many times.
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Chris: I know.
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Everyone.
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It's like it knows, isn't it?
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Jen: I know.
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Chris: Yeah.
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And it's a genuinely common pattern, isn't it?
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And the timing fits because, um, there's reasonable evidence that this low-grade
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inflammation feeds into some autoimmune conditions too, so things like, uh, lupus
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or rheumatoid, rheumatoid arthritis.
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Though, it's worth saying that this is an association researchers are still focusing
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on, so there's not full-on conclusions yet, just to put the caveat out there.
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Jen: Yeah.
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And that caution matters because the honest version is more
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useful than the scary one.
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The better established story is the brain, the hippocampus, which is central to
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your memory and learning, is especially sensitive to a long soak in cortisol,
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and it can actually shrink a little, which makes your memory, it can make
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your memory and focus feel foggier.
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Mm. Which is never a good thing when you're trying to live day to day.
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Jamie: So the walking into a room and forgotting, forgetting why you went there
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thing is, uh, is not you being hopeless.
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It's just chemistry.
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Chris: Largely, yes.
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And, uh, naming it that way is actually kinder, I guess, a
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bit more generous and accurate.
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Um, and th- there's even work or research that's shown that our brain's cell, um,
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telomeres, which are the protective caps that are on the end of our DNA, were
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about twice as long in healthy people as in people with major depression.
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So chronic stress does actually seem to age people faster.
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Jen: And the simplest effect of it all is the muscles.
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So under stress, your muscles brace like almost like a flinch and, you
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know, they're meant to let go once it passes, but stay braced for weeks
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and you get those, like, tension headaches, your tight neck, your
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aching lower back, and you probably don't think of stress as the cause.
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Jamie: Tight neck I can confirm, and the gut's on the same list.
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That off-your-food feeling when you're feeling stressed.
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Chris: Absolutely.
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It's de- it's definitely on the same list.
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Mm. So digestion actually is one of the first jobs that the body
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drops in order to kind of deal with a, an immediate emergency,
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um, when it's being stressed out.
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So when you are stressed, that's why you often get this kind of knotted
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or queasy feeling in the tummy.
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Jen: Oh, that's such a horrible feeling, isn't it?
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Mm. I get that sometimes.
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But it, these effects, they don't hit everyone the same.
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So there was a Mental Health UK burnout report found 9 in 10 people had felt high
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or extreme stress in the past year, and the 18 to 34s are the, are carrying most
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of it, and a lot of those stresses were tied to work, money, and working hours.
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Chris: It makes sense, doesn't it?
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'Cause, you know, the 18 to 34, you know, the age group we're all in-
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Jen: Yeah, yeah, yeah … of course, yeah.
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Chris: Yeah.
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That's often the stage of life that we've got the kinda least control, um, over
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your time, but the most uncertainty ahead.
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So the same pressure lands harder when you're rushing around or, you know,
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you can't see the wood for the trees.
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Jen: Yeah, yeah.
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Jamie: And can we kill the unhelpful myth while we're at it,
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it's all in your head, just relax?
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As if you could think your blood pressure back down by deciding to.
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Jen: Can you imagine if you could do that?
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Chris: Yeah.
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The power
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Jen: Yeah, I agree.
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You know, but thoughts are real.
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We have to acknowledge that.
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And then, but so is everything downstream of them, so like the
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raised heart rate, the cortisol, the suppressed immune response.
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None of it's imaginary, and so telling someone it's all in their head, which
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I'm sure happens a lot, it's both unkind and it's frankly wrong, isn't it?
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Chris: Yeah, absolutely right.
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And of course, it, it cuts both ways, doesn't it?
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Because, because the response is physical, the things that calm it when it comes
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to stress are often physical too.
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So you don't have to somehow win an argument with your own brain to make
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a difference, and in fact, you might get a few funny looks if you're trying
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to argue with yourself in public.
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Let's be honest.
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Jamie: Right.
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The bit I've been waiting for, what actually moves the needle, and
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what's just a nice-sounding noise?
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Chris: So by a distance, the strongest evidence is for
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movement, probably unsurprisingly.
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Mm. So research consistently shows that physical activity reliably lowers
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cortisol and improves sleep, and this has been reported in multiple studies.
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Um, importantly though, it's the dose is far gentler than most people realize.
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So you're only talking about 20 minutes or so of something moderate.
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So most days, if you do s- some kind of moderate exercise, even
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brisk walking, that makes a colossal difference to managing stress.
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Jen: Which I love this because as a runner, I'll take any excuse, um, to
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get outdoors and to move your body.
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But the real headline is consistency beats intensity, doesn't it?
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So a steady walk you keep up does far more than that occasional heroic session
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that you dread and abandon- Yeah … and then you're sore for days afterwards.
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Jamie: Yes, and without sounding like a motivational quote, the best exercise
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is one that you will actually do.
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Jen: Yeah, absolutely.
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Chris: You always sound like a motivational quote.
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Uh, but you're absolutely right.
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And, um, then we've got the kind of in the, in-the-moment
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option, I suppose we'll call it.
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Which, uh, so the fastest tool to kind of de-stress is to work on your breathing.
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So we should all do this together.
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So a double inhale through the nose, then a long, slow exhale through the
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mouth, and in this kind of exercise, it's the out breath that, which is
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the active part because it's gently putting the brakes on your heart rate.
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And so just like the movement approach, it's something really straightforward
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to do that makes a big difference.
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Jen: Yeah.
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Jamie: But a word of warning with the breathing technique,
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do it discreet, discreetly.
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A big dramatic sigh in a meeting might reflect badly on the last
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person's comment who just spoke.
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Jen: Yeah.
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Chris: That's true.
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It takes me back to the yawning episode we did.
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I, I couldn't stop yawning- … all the way through that, uh, episode.
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Yeah.
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Jen: You know, and that office sigh is a loaded gesture, but it, it
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works maybe without the theater.
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Um, but the slower tools are, are strong too.
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So there's good evidence that an eight-week mindfulness course around
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10 to 20 minutes a day actually lowers cortisol, um, and gives the
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brain a bit of a nudge as well.
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Chris: Yeah, definitely.
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And, um, there was one trial that found that kind of course held up about as well
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as a common anxiety medication, actually.
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Uh, but I need to put my Captain Sensible hat on again, as always.
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Always.
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Uh, that please don't take that comment as a recommendation to
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swap your medication for an app.
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Jen: Yeah,
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Chris: definitely.
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So if you're taking medication and thinking about changing direction,
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always speak to your doctor.
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Jen: Yeah.
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Jamie: Sensible.
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Easy to run too far with a headline like that.
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Jen: Yeah, definitely.
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Chris: Uh, yeah.
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I've always got to put the disclaimers in, you know-
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Jen: Yeah,
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Chris: um- … just, just in case
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… Jen: we love a, a Captain Sensible
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Chris: air.
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Yeah.
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I know.
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I have to fight for the Captain Sensible fit.
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In fact, where's Matt?
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Uh, Matt will sometimes try to take it off me.
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Oh, so two more points that have solid backing here.
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So the first is sleep and stress feed each other, which is no surprise.
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Mm. So we know that poor sleep, oh, sorry, poor stress makes you, you more
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reactive, and stress wrecks your sleep.
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So working on your sleep has a huge impact on stress, but indeed,
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working on stress has a huge impact on sleep Um, the other is simply
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actually being around other people.
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Yeah.
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So regular social contact measurably steadies the stress chemistry.
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Jen: That's interesting.
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Jamie: So a walk with a friend is basically a double dose, movement
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and socializing at the same time.
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Chris: Absolutely.
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Jen: Yeah.
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It ticks several boxes at once.
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Um, and diet is another one people think about.
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So just to be straight, the evidence with diet impacting stress, it's much thinner.
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Um, there is early work that omega-3 fatty acids might blunt the body's
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blood pressure response to stress a little, but it is emerging, it's not
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proven, and I wouldn't oversell it.
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Jamie: And I'm the last person who should oversell it, given that I
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co-own a company that sells omega-3.
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Our omega-3 is a good product.
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It's not a stress cure, and I'd rather tell you that plainly
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rather than dressing it up.
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Jen: Yeah.
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Chris: I think we've got to kind of flash a product in
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front of the screen, you know.
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Yeah.
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We're not trying to sell it, you know, or make any claims.
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Um, I'm gonna put my last Captain Sensible hat on again- Yeah … if you don't mind.
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Um, if stress is genuinely affecting your health, your sleep, your mood,
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et cetera, that's a conversation with a doctor, not a podcast.
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So the support out there is strong when it comes to stress, and using it is smart.
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It's not a failure.
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No.
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It's really important to
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Jen: point that
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Jamie: out.
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Mm. So why does stress make us feel ill?
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Jen: Because the body has a fast, powerful emergenc- emergency response that it's
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super for, like, a short scramble.
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It raises your heart rate, floods you with energy, and switches
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off everything non-essential.
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The harm isn't in switching it on.
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It's n- in never switching it off.
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So the heart, the immune system, brain, the gut, they all spend months
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running in a state that was actually only ever meant to last minutes.
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Jamie: So the goal was never a stress-free life.
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That doesn't actually exist anyway.
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Mm. It's actually making sure the guests at my dinner
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party- … actually leave eventually.
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Hobs back down, washing up done, the kitchen back to itself, um,
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before the next lot turn up.
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Chris: And that's the key point.
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Maybe not the dinner party, but the key point is you're not broken for feeling it.
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Jen: Yeah.
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Chris: You just need the off switch to work as well as the on switch
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does when it comes to stress.
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Jen: Yeah, definitely.
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So that is it for this week.
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Make sure you hit that subscribe button.
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We're unpacking the science behind everyday questions each week.
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Tell us in the comments what you'd like us to explore next.
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Thanks for geeking out with us, but for now, that's it from me.
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Jamie: That's it from me.
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Chris: And that's it from me.
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Jen: Bye for now