When your gut feels your stress: understanding the IBS and mental health link
You've had a stressful week. Deadlines have stacked up, sleep has slipped, and by Friday your stomach is bloated, your bowels are unpredictable, and you feel wiped out.
If you have IBS, this isn't a coincidence. The gut and the brain are wired together, and what happens in one shows up in the other. Here's how that actually works.
The gut–brain axis, in plain English
The main connection between gut and brain is the vagus nerve, which runs from the brainstem all the way down into the abdomen. Signals go both ways, but mostly upward. The gut has more to say to the brain than the other way round.
The gut also runs its own nervous system, the enteric nervous system. Hundreds of millions of nerve cells, sometimes called the "second brain." It handles most of digestion without needing input from above. It also makes a lot of the body's serotonin, which is where this gets misunderstood.
You've probably seen the line that 90% of your serotonin is in your gut, usually followed by something about mood. It's true that most serotonin is made in the gut. It just doesn't reach the brain. There's a barrier in the way, and the two pools stay separate. What gut serotonin actually does is regulate motility and local signalling. Mood is influenced by the gut, yes, but through different routes: the vagus nerve, microbial metabolites, immune and hormonal signalling.
Add the microbiome to that, with its own effects on nerves and immunity, and you've got a system where stress, sleep, mood and digestion are genuinely tangled up in each other. Not metaphorically. Physically.
Why stress and mood affect IBS symptoms
Under sustained pressure, the nervous system shifts gear. A few things follow.
Motility changes. Food moves through the gut faster or slower than usual. Some people get diarrhoea under stress, others get constipated. Same trigger, different output.
Visceral hypersensitivity. The nerves in the gut become more reactive, so sensations that wouldn't normally register start to feel uncomfortable or painful. This is thought to be one of the core mechanisms in IBS, and it's a big part of why symptoms can feel out of proportion to what you've eaten.
Sleep gets worse. Poor sleep raises stress hormones the next day, which can worsen gut symptoms, which then disrupts sleep again. It becomes a loop, and it's surprisingly hard to break without doing something deliberate about it.
Eating patterns shift. Skipped meals, eating on the go, more caffeine, fewer plants. None of this is a moral failing, it's what stressed humans do, but the gut notices.
This is why two people on the same diet can have completely different symptoms, and why the same person can react differently to the same meal on different days. Diet matters. It's just rarely the whole story.
Five practical things you can try this week
None of these are quick fixes. They're foundations, and they consistently help.
- Anchor your meals. Three meals a day, roughly the same times, sitting down, away from your laptop. Erratic eating is one of the most common drivers of IBS symptoms I see in clinic, and one of the easiest to change.
- Slow down before you eat. Sixty seconds of slower breathing before a meal shifts the nervous system into a state that's actually built for digesting food. Long exhales are the part that does the work.
-
Protect sleep like it matters. Consistent sleep and wake times, low light in the evening, screens off before bed. None of this is glamorous, all of it helps.
- Move daily, gently. A twenty to thirty minute walk, outside if possible. Motility, mood and sleep all benefit from it. You don't need to train hard for any of this to work.
- Track patterns, not foods. A short daily note covering meals, sleep, stress level and bowel habit, kept for two or three weeks, usually tells you more than any elimination diet. Look across the week, not at single meals.
When self-management isn't enough
These are foundations, not diagnostics. If your symptoms are persistent, or if you've noticed unexplained weight loss, blood in your stools, symptoms that wake you at night, or there's a family history of bowel cancer or inflammatory bowel disease, please see your GP. IBS is a diagnosis of exclusion. Other conditions need to be ruled out first.
Beyond that, if you've already been diagnosed and you're still stuck in a cycle of restriction, flare-ups and second-guessing every meal, more structured support is usually what shifts things. The aim isn't fewer foods. It's a calmer gut, a calmer nervous system, and a clearer picture of what's actually driving your symptoms.
Reframe how you view things
The gut and the nervous system aren't separate systems that occasionally interfere with each other. They're one system, observed from two angles. Treating them that way, in how you eat, sleep, move and recover, is usually where progress comes from. That's true whether or not it's Mental Health Awareness Week. This is just a good week to say it.
About the author
Teddy is a UK-based nutritional therapist specialising in chronic digestive issues including IBS and SIBO. He helps clients move from restriction and confusion to structured, root-cause clarity, with a focus on practical, evidence-informed support rather than restrictive protocols.
You can find out more about his work here:
https://berkeleynutrition.co.uk/ and make sure you're following him on IG for tips and advice: @berkleynutrition
