SIBO

 

SIBO, Stress, and Burnout: Understanding the Vicious Cycle Between the Intestines, Stomach, and Nervous System

 

SIBO isn't just about bacteria

SIBO—Small Intestinal Bacterial Overgrowth—is often summed up as simply, “There are too many bacteria.”

But this explanation is far from sufficient.

SIBO is a multifactorial condition involving factors such as gastrointestinal motility, the migrating motor complex, anatomical abnormalities, immunity, bile, gastric acidity, and interactions between the microbiota and the nervous system. Recent studies also emphasize the role of the gut-brain axis. [14]

And among the factors that can perpetuate this imbalance, there is one that is often overlooked: chronic stress.

Even more interesting: the relationship works both ways.

Stress can disrupt digestive function, while chronic digestive disorders can themselves contribute to the activation of the stress response.

Chronic stress directly affects the digestive system

The brain and the digestive tract are constantly communicating with each other.

This communication occurs primarily through the autonomic nervous system, the vagus nerve, stress hormones, the immune system, neurotransmitters, and metabolites produced by the microbiota.

Today, we're talking about the microbiota-gut-brain axis.

And this connection works both ways: the brain influences the gut, but the gut also influences the brain. [2, 3]

Scientific data show that acute stress—and especially chronic stress—can alter several gastrointestinal parameters: motility, intestinal permeability, visceral sensitivity, immune function, and the microbiota. [1]

This helps explain why a person who has been under intense pressure for a long time may gradually develop or experience worsening digestive symptoms.

Stress, exhaustion, and burnout: It isn't necessarily depression

It is important to make a distinction.

Burnout is not the same as depression.

Burnout is a state of exhaustion associated with chronic work-related stress, whereas depression is a distinct psychiatric disorder.

However, both can share certain symptoms: fatigue, sleep disturbances, difficulty concentrating, loss of energy, or decreased motivation.

In the context of SIBO, what interests us most is the chronic stress burden and its physiological consequences.

When the stress response remains active for a long time, digestion can be disrupted.

Stress can affect, among other things, motility, digestive secretions, visceral sensitivity, the intestinal barrier, and the microbiota. [1]

The circle can also work the other way around

A person who suffers for months from bloating, abdominal pain, diarrhea or constipation, acid reflux, discomfort after meals, fatigue, food intolerances, or sleep disturbances may gradually develop a state of digestive hypervigilance.

Eating becomes a source of anxiety. Every symptom becomes a cause for concern. Sleep may suffer. And stress levels rise even further.

Studies of people with SIBO have found, in particular, higher levels of stress and anxiety than in control subjects, although these studies do not prove that SIBO is the direct cause of this psychological condition.

This is an important distinction: correlation does not imply causation.

But from a biological standpoint, a vicious cycle is plausible and consistent with the available data on the gut-brain axis.

What about the stomach? Stress can play a role there, too

The stomach has an extremely sophisticated defense mechanism against its own acidic contents.

This protection involves, in particular, mucus, bicarbonates, mucosal blood flow, cell turnover, the immune system, nitric oxide, and prostaglandins.

Prostaglandins play an important role, in particular, in maintaining the integrity of the mucosa, in its defense mechanisms, and in its ability to repair itself. [8]

The protection of the gastric mucosa therefore relies on a set of complementary and interdependent mechanisms.

When these defense mechanisms are disrupted, the mucosa may become more vulnerable to damage and less able to maintain its balance and repair capabilities.

Experimental studies show, in particular, that certain pathways involved in prostaglandin production play a role in the protection and repair of the digestive tract lining. [5, 6, 7]

It would therefore be more accurate to view the gastric mucosa as a dynamic protective system, whose balance depends on many factors: mucus, bicarbonates, blood supply, cell turnover, local mediators, the immune system, and nervous system regulation.

Severe forms of stress can, in particular, cause vascular changes and mucosal ischemia, contributing to stress-related gastrointestinal lesions. [8]

The gastric mucosa is therefore not protected by a single molecule: it is an entire defense system.

And what about stomach acid in all of this?

Gastric acidity serves as an important antimicrobial barrier.

Experimental and human studies have shown that stomach acid can destroy a large proportion of ingested bacteria. When stomach acid is significantly reduced or absent, this barrier becomes much less effective. [9]

This explains why hypochlorhydria is considered a factor that may promote bacterial overgrowth in the small intestine.

But we need to correct a very common misconception here: stress or burnout does not automatically lead to a loss of stomach acid.

The response of gastric secretion to stress is complex and can vary depending on the type and duration of the stress. Therefore, studies do not allow us to simply say, “Stress = more acid” or “Stress = less acid.”

The physiological reality is much more nuanced.

On the other hand, a reduction in the acid barrier is likely to promote the survival and passage of bacteria into the intestine.

When acidity decreases, conditions may become more favorable for SIBO

This, in particular, explains the scientific interest in medications that significantly reduce gastric acid secretion, such as proton pump inhibitors (PPIs).

Several meta-analyses have found an association between the use of PPIs and an increased risk of SIBO. A 2013 meta-analysis had already identified such an association, and subsequent studies have confirmed this trend. [10, 11, 12]

However, we must remain cautious: these results primarily show an association, with significant heterogeneity among the studies.

Therefore, it cannot be said that taking a PPI will automatically cause SIBO.

Can SIBO contribute to stress?

That's where the model becomes particularly interesting.

A person who develops SIBO may begin to experience severe bloating, followed by pain, digestive issues, and persistent fatigue. They change their diet, cut out more and more foods, sleep less well, and worry about their symptoms.

His stress levels are rising.

However, stress itself can disrupt motility, digestive sensitivity, intestinal permeability, and the microbiota. [1]

We can therefore conceptualize the phenomenon as follows:

SIBO → digestive symptoms → stress → disruption of the gut-brain axis → digestive dysfunction → conditions that promote the persistence of symptoms.

This does not mean that stress is the cause of all cases of SIBO.

This means that, for some people, stress can become a factor that perpetuates the problem.

SIBO, a fragile digestive lining: Why We Need to Be Cautious with Antimicrobials

We need to move away from a very simplistic way of thinking: “I have too many bacteria, so I have to kill the bacteria.”

Treating SIBO first requires understanding why it developed and why it keeps coming back.

Is motility normal? Is there hypochlorhydria? Has the patient been taking PPIs for a long time? Is there an anatomical abnormality? Is there an underlying digestive disorder? Is there a Helicobacter pylori infection? Is there severe constipation?

The condition of the digestive tract lining is also important.

A person with a particularly sensitive or compromised stomach lining may not tolerate a concentrated antimicrobial agent as well.

What about essential oils, like oregano?

Oregano essential oil is often mentioned in natural approaches to SIBO because of the antimicrobial activity of some of its compounds.

There is indeed some interesting clinical data on herbal preparations [14]

Why "killing bacteria" isn't always enough

If the underlying problem is poor motility, hypochlorhydria, an anatomical abnormality, or another condition that promotes bacterial overgrowth, temporarily eliminating the bacteria does not necessarily address the underlying cause.

This is one of the reasons why SIBO often recurs.

We must therefore consider the underlying factors: microbiota, motility, gastric acidity, the mucosal lining, diet, sleep, stress, the autonomic nervous system, and any underlying digestive disorders.

The Real Vicious Cycle

Chronic stress --> disruption of the gut-brain axis and digestive function --> changes in motility, secretions, the intestinal barrier, and the microbiota --> a potentially favorable environment for digestive disorders and, in some people, SIBO --> bloating, pain, bowel movement issues, fatigue, sleep disturbances --> increased stress and digestive hypervigilance --> further disruption of the gut-brain axis

Contemporary research increasingly confirms the importance of this two-way communication between the brain, the gut, and the microbiota, although the precise mechanisms and causality in humans have yet to be better defined. [2, 3]

Conclusion

SIBO should therefore not be viewed solely as a problem caused by “bad bacteria.”

It is sometimes a visible symptom of a digestive system in which several regulatory mechanisms are disrupted.

Chronic stress may play an important role in this process, particularly through the gut-brain axis, motility, intestinal permeability, and the microbiota.

For its part, SIBO and its symptoms can contribute to maintaining stress.

The gastric mucosa also has its own protective mechanisms, including mucus, bicarbonates, blood supply, cell turnover, and prostaglandins. Together, these various mechanisms help maintain the mucosa’s integrity and repair capacity. [5, 6, 7, 8]

Finally, gastric acidity serves as an important antimicrobial barrier. A reduction in this barrier can promote bacterial survival and has been associated with an increased risk of SIBO in several studies, particularly among people taking PPIs. [9, 10, 11, 12]

So the question isn't just:

"How do you kill bacteria?"

But also:

"Why were these bacteria able to take hold? And what is preventing my digestive system from regaining its balance today?"

That is probably where a truly comprehensive approach to treating SIBO begins.

Scientific References – PubMed

1. Leigh SJ, et al. The impact of acute and chronic stress on gastrointestinal physiology and function: a microbiota-gut-brain axis perspective. J Physiol. 2023. PMID: 37756251.

2. Margolis KG, Cryan JF, Mayer EA. The Microbiota-Gut-Brain Axis: From Motility to Mood. Gastroenterology. 2021.

3. Kim YK, et al. Understanding the Connection Between the Gut-Brain Axis and Stress/Anxiety Disorders. Curr Psychiatry Rep. 2021. PMID: 33712947.

4. Santos J, et al. Stress, the microbiota, and the gut-brain axis in mental and digestive health. Med Clin (Barc). 2025. PMID: 39824687.

5. Peskar BM, et al. Role of cyclooxygenase isoforms in gastric mucosal defense. J Physiol Paris. 2001. PMID: 11595412.

6. Brzozowski T, et al. Expression of cyclooxygenase (COX)-1 and COX-2 in adaptive cytoprotection induced by mild stress. J Physiol Paris. 2000. PMID: 10791687.

7. Wallace JL. Prostaglandins, NSAIDs, and gastric mucosal protection: Why doesn't the stomach digest itself? Physiol Rev. 2008. PMID: 18923189.

8. Laine L, Takeuchi K, Tarnawski A. Gastric Mucosal Defense and Cytoprotection: From the Lab to the Clinic. Gastroenterology. 2008. PMID: 18549814.

9. Giannella RA, Broitman SA, Zamcheck N. The gastric acid barrier to ingested microorganisms in humans: in vivo and in vitro studies. Gut. 1972. PMID: 4556018.

10. Lo WK, Chan WW. Proton pump inhibitor use and the risk of small intestinal bacterial overgrowth: a meta-analysis. Clin Gastroenterol Hepatol. 2013. PMID: 23270866.

11. Su T, et al. Meta-analysis: Proton pump inhibitors moderately increase the risk of small intestinal bacterial overgrowth. J Gastroenterol. 2018. PMID: 28770351.

12. Khurmatullina AR, et al. The Duration of Proton Pump Inhibitor Therapy and the Risk of Small Intestinal Bacterial Overgrowth: A Systematic Review and Meta-Analysis. J Clin Med. 2025. PMID: 40649078.

13. Chedid V, et al. Herbal therapy is as effective as rifaximin for the treatment of small intestinal bacterial overgrowth. Glob Adv Health Med. 2014. PMID: 24891990.

14. Small Intestinal Bacterial Overgrowth: Microbiome Dysregulation, Disruption of the Gut-Brain Axis, and Systemic Consequences. 2026. PMID: 42378001.

Important note: This article is intended for general information purposes only. It is not intended to diagnose SIBO, hypochlorhydria, or burnout. Persistent or severe digestive pain, vomiting, gastrointestinal bleeding, or unexplained weight loss require medical evaluation. Oral use of essential oils, particularly oregano essential oil, requires special caution in cases of an irritated digestive tract lining, such as gastritis.