Can anxiety cause stomach problems?

Yes. When your brain perceives a threat, it activates the fight-or-flight response, which diverts blood away from your digestive system and changes gut motility. This can cause nausea, cramping, diarrhea, or a churning feeling in your stomach — even when there is no physical danger.

Why does my stomach hurt when I'm anxious?

Your gut has its own nervous system — the enteric nervous system — with over 100 million neurons. It communicates directly with your brain through the vagus nerve. When anxiety activates your stress response, those signals travel to your gut and can cause pain, cramping, bloating, and changes in digestion.

Is there a link between IBS and anxiety?

There is a strong connection. Research consistently shows that people with irritable bowel syndrome are significantly more likely to have an anxiety disorder, and people with anxiety are more likely to develop IBS. The relationship goes both ways — gut distress can trigger anxiety, and anxiety can trigger gut symptoms.

Can improving gut health reduce anxiety?

There is growing evidence that supporting gut health may help reduce anxiety symptoms, though it is not a replacement for professional treatment. Eating a varied, fibre-rich diet, reducing processed foods, managing stress, and staying physically active all support a healthier gut microbiome, which in turn supports better communication along the gut-brain axis.

The Gut-Brain Connection: How Anxiety Affects Your Stomach (and Vice Versa)

You know the feeling. Something stressful happens — a difficult conversation, a looming deadline, a sudden wave of worry — and within minutes, your stomach responds. A knot tightens below your ribs. Nausea creeps in. Maybe your appetite vanishes, or you suddenly need to find a bathroom. This is not a coincidence, and it is not "all in your head." The gut-brain connection is one of the most well-documented pathways in the human body, and understanding how it works can change the way you think about both anxiety and digestion.

Your Gut Has Its Own Brain

Deep in the walls of your gastrointestinal tract, from your oesophagus to your rectum, lies a network of over 100 million neurons. This is the enteric nervous system (ENS) — sometimes called the "second brain" — and it is the largest collection of nerve cells outside your actual brain and spinal cord.

The ENS does not think in the way your brain does. It cannot write poetry or solve equations. But it independently controls digestion: the rhythmic contractions that move food through your intestines, the release of enzymes, the regulation of blood flow to the gut lining. And critically, it uses many of the same neurotransmitters your brain uses — including serotonin, dopamine, and GABA.

In fact, roughly 95 percent of your body's serotonin is produced in the gut, not the brain. Serotonin is best known for regulating mood, but in the gut it controls motility — how quickly food moves through your system. When something disrupts serotonin signalling in either direction, both your mood and your digestion can be affected.

How the Gut and Brain Talk to Each Other

The gut and brain are in constant two-way communication through what scientists call the gut-brain axis. This is not a single wire — it is a network of pathways working in parallel:

Pathway	What it does
Vagus nerve	The main physical highway — carries signals in both directions between the brainstem and the gut. About 80% of its fibres are afferent, meaning they send information from the gut to the brain.
HPA axis	The hypothalamic-pituitary-adrenal axis — your body's central stress-response system. When activated, it releases cortisol, which directly affects gut motility and permeability.
Immune signalling	Gut inflammation can trigger immune molecules (cytokines) that cross into the brain and influence mood and anxiety.
Microbial metabolites	The trillions of bacteria in your gut produce short-chain fatty acids, neurotransmitters, and other molecules that influence brain function.

The vagus nerve deserves special attention. It is the longest cranial nerve in your body and acts as a direct phone line between your gut and your brain. Research shows that vagal tone — how well your vagus nerve functions — is closely linked to emotional regulation. Higher vagal tone is associated with greater resilience to stress; lower vagal tone is associated with anxiety and difficulty recovering from stressful events.

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Why Anxiety Wrecks Your Stomach

When your brain perceives a threat — real or imagined — it triggers the fight-or-flight response. Your sympathetic nervous system fires up, flooding your body with adrenaline and cortisol. This is designed to prepare you for physical action, and it comes with a clear set of priorities: blood and energy go to your muscles, heart, and lungs. Everything non-essential gets deprioritised — including digestion.

Here is what that looks like in your gut:

Blood flow to the digestive tract drops. Your body redirects it to your skeletal muscles. This can cause that hollow, churning feeling in your stomach.
Gut motility changes. Stress can either slow digestion (leading to bloating and constipation) or speed it up dramatically (leading to cramping and diarrhea). The direction depends on the individual.
Stomach acid production shifts. Anxiety can increase acid secretion in some people, contributing to nausea and acid reflux.
The gut barrier becomes more permeable. Chronic stress can weaken the tight junctions between cells in the intestinal lining — sometimes called "leaky gut" — allowing inflammatory molecules to pass through.
The gut microbiome changes. Sustained stress alters the composition of your gut bacteria, reducing beneficial species and increasing those associated with inflammation.

The result is that anxiety does not just make your stomach feel bad — it physically changes how your gut operates.

The Bidirectional Problem: Your Gut Talks Back

Here is the part that most people miss: the connection works in both directions. A troubled gut does not just respond to anxiety — it can generate it.

Research published in multiple journals has found that people with gastrointestinal conditions like irritable bowel syndrome (IBS) are significantly more likely to have anxiety or depression than the general population. For a long time, doctors assumed the anxiety came first and the gut symptoms followed. But newer research suggests it often works the other way around — gut disturbances send distress signals up the vagus nerve to the brain, which can trigger or amplify anxiety.

Harvard Health describes it clearly: "A person's stomach or intestinal distress can be the cause or the product of anxiety, stress, or depression." The brain and the gut are so intertwined that trying to treat one without addressing the other often fails.

This is why people with chronic gut issues sometimes develop health anxiety — the constant discomfort creates a feedback loop where gut symptoms trigger worry, and worry worsens gut symptoms.

What You Can Actually Do About It

Because the gut-brain axis is bidirectional, calming either end of the connection can help the other. Here are approaches supported by evidence:

Slow your breathing. Deep, diaphragmatic breathing directly stimulates the vagus nerve, which is the fastest way to shift your nervous system from fight-or-flight to rest-and-digest. A breathing pace of roughly six breaths per minute has the strongest calming effect on vagal tone.
Eat more fibre and fermented foods. A diverse, fibre-rich diet supports a healthier gut microbiome. Foods like vegetables, whole grains, legumes, yoghurt, kefir, and kimchi provide both fibre and beneficial bacteria. A meta-analysis found that probiotics and synbiotics may help reduce anxiety symptoms, though the evidence is still developing.
Move your body. Regular physical activity improves gut motility, increases microbial diversity, and reduces cortisol. You do not need intense exercise — even a daily walk has measurable effects on both gut health and anxiety.
Reduce ultra-processed foods. Diets high in refined sugar and additives are associated with reduced microbial diversity and increased gut inflammation — both of which can worsen anxiety through the gut-brain axis.
Address the anxiety directly. If gut symptoms are being driven by chronic stress or an anxiety disorder, techniques like cognitive behavioural therapy (CBT) have strong evidence for improving both the psychological and gastrointestinal symptoms. The American Gastroenterological Association now recognises brain-gut behaviour therapies as a treatment for IBS.
Talk to a professional. If you have persistent gut symptoms alongside anxiety — especially if they are affecting your daily life — see a healthcare professional. Conditions like IBS, functional dyspepsia, and anxiety disorders are treatable, and addressing both the gut and the mind together tends to produce better outcomes than treating either alone.

Try It in Unxiety

When anxiety hits your stomach, the fastest way to intervene is through the vagus nerve. Open Unxiety and head to the Breathe tab — guided patterns like box breathing and extended-exhale breathing directly stimulate vagal tone, shifting your body from fight-or-flight to rest-and-digest. If anxious thoughts about your symptoms are spiralling, the Cards tab offers cognitive reframing prompts to help you challenge the catastrophic thinking that feeds the gut-brain loop.