Many people living with chronic digestive issues notice that their symptoms often get worse when they’re stressed, and their mood often drops when their gut is flaring. Yet patients are frequently told, “it’s just anxiety,” or “your symptoms are in your head.”

Current research paints a very different picture. The gut and the brain are deeply interconnected, and disruptions in one can directly influence the other. Stress can slow digestion and worsen SIBO symptoms. SIBO, in turn, can influence mood, energy, and emotional well-being through biological pathways we now understand much more clearly.

The SIBO Awareness team explains how the gut–brain connection works, how SIBO can affect mental health, how mental health can affect SIBO, and what you can do to support both systems.

I. The Gut–Brain Axis: Your Body’s Internal Communication Network

Scientists often describe the gut and the brain as being in “constant conversation.” This communication loop is called the gut–brain axis, and it includes the vagus nerve, neurotransmitters made in the gut, the immune system, and chemical signals released by intestinal microbes.

About 95% of the body’s serotonin¹—a neurotransmitter important for mood, sleep, and emotional balance—is produced in the gut, not the brain. When the gut is inflamed, overgrown with bacteria, slowed by motility problems, or disrupted by SIBO, its communication with the brain becomes strained. Signals that normally support calm digestion and balanced mood can instead amplify discomfort, stress, or emotional symptoms.

Research also shows that people with depression and anxiety often have measurable differences in their gut microbiome², including lower microbial diversity and higher inflammatory activity. Because SIBO is a form of dysbiosis—specifically an overgrowth of microbes where they don’t belong—it can contribute to similar disruptions.

II. How Gut Health Influences Mental Health

The connection between gut health and emotional well-being is strong and well documented. A balanced gut supports the production of neurotransmitters, regulates stress responses, and influences how the brain processes emotional information. A disrupted gut can shift these signals, increasing stress sensitivity or contributing to low mood.

One well-studied example involves tryptophan, an amino acid used to make serotonin. In people with both SIBO and depression, research shows that tryptophan is diverted away from serotonin production and toward the kynurenine pathway³—a process associated with inflammation and low mood. When SIBO is treated, both gut and emotional symptoms often improve together⁴.

III. How SIBO Can Affect Mental Health

SIBO can influence mood, energy, emotional resilience, and the body's stress response through several mechanisms. Studies show that individuals with SIBO often have higher depression scores⁵, likely related to altered serotonin pathways, inflammation, or nutrient malabsorption. Treatment of SIBO has been shown to improve emotional well-being in some patients.

Anxiety is also common among people with SIBO. Some anxiety arises from the symptoms themselves—bloating, discomfort, and food fear—but physiological mechanisms play a role as well. People with SIBO show higher stress and anxiety scores⁶ than healthy controls, and improvements in SIBO are often associated with improvements in anxiety levels and overall quality of life⁷.

Chronic symptoms such as bloating, brain fog, fatigue, and nutrient malabsorption can understandably affect emotional health. This combination of physiological and psychological factors makes emotional support a meaningful part of comprehensive SIBO care.

IV. How Mental Health Can Make SIBO Worse

Mental health, especially stress and anxiety, can directly influence the development, severity, and persistence of SIBO. Chronic stress slows gut motility—the muscle contractions that keep food and bacteria moving through the small intestine. When motility slows, bacteria have more time to accumulate, increasing the likelihood of SIBO.

Research on hydrogen sulfide–producing bacteria shows that norepinephrine, a stress hormone, can stimulate the growth of the microbes involved in H₂S-dominant SIBO⁸. Stress also weakens vagal tone, decreasing the body’s ability to regulate digestion. Irregular eating patterns, common during times of stress or anxiety, weaken the migrating motor complex, further increasing SIBO risk.

V. Breaking the Cycle: Supporting Gut and Mental Health Together

Because SIBO and mental health influence each other, the most effective healing strategies support both sides of the gut–brain axis. Treating SIBO directly—through antimicrobial therapy, diet, and motility support—can improve both gut symptoms and emotional well-being⁹. For many people, improvements in digestion naturally improve energy, mood, and clarity.

Supporting mental health is also essential. Practices such as slow breathing, gentle movement, structured eating, restorative sleep, and emotional support help strengthen the nervous system’s “rest and digest” response, improving motility and supporting the gut’s ability to heal. These practices complement medical treatment and make long-term recovery more stable.

Over time, routines that support both the gut and the brain—regular meals, balanced nutrition, hydration, and consistent stress reduction—help restore the communication pathways that keep the digestive system functioning smoothly.

VI. You Are Not Imagining It: A Message of Validation

Many people with SIBO are told that their symptoms are “just anxiety,” or that emotional distress means their condition is psychological. The science tells a different story. SIBO can influence mood, focus, and emotional resilience, and stress can physiologically worsen SIBO by slowing motility and altering microbial growth. These interactions are real and well documented.

As we move into seasons of higher stress—holidays, travel, busy schedules—remember that caring for your mind is part of caring for your gut. And caring for your gut is part of caring for your mind. Both sides of the gut–brain connection deserve support and compassion. Healing the gut–brain axis takes time, but it can transform not only digestive symptoms—it can transform overall well-being.