Scientists have found that when the stomach and brain are synced too strongly, it may signal worse mental health, linking anxiety, depression, and stress to an overactive gut-brain connection.
The abundance of recent research into the gut-brain connection has demonstrated how important the link is between the two organs, and how their communication can affect mood and mental health. There has been less research into the link between the stomach’s inherent rhythmic activity and mental well-being.
In a new study, researchers from Aarhus University in Denmark set out to discover whether the strength of the stomach-brain connection is linked to a person’s mental health profile.
“The stomach’s connection to the brain may actually be too strong in people under psychological strain,” said the study’s co-lead and corresponding author Leah Banellis, PhD, a postdoctoral researcher at Aarhus’ Department of Clinical Medicine and the Center of Functionally Integrative Neuroscience (CFIN).
The complex enteric nervous system, which controls the digestive system, is often referred to as the “second brain” or the “brain in your gut” because it contains more neurons than the entire spinal cord – over 100 million – and can operate somewhat independently from the central nervous system. The stomach is always contracting and expanding, even when it’s not moving food through the digestive tract, with rhythmic bioelectrical waves occurring roughly once every 20 seconds.
While these contractions are part of normal digestion, recent research has shown that the stomach’s rhythm is closely linked to brain activity via the vagus nerve. Changes in this synchrony may influence mood, stress responses, and cognitive function, making it a promising, but underexplored, area for mental health research.
The researchers recruited 243 people aged 18 to 47, ranging from mentally healthy to those with significant symptoms of mood disorders such as anxiety and depression, in addition to those with ADHD, autism, insomnia, and other issues. Electrogastrography (EGG) was used to measure the stomach’s natural electrical rhythm, functional MRI (fMRI) measured brain activity while participants were at rest, and 37 validated, self-report questionnaires scored anxiety, depression, stress, fatigue, sleep, quality of life, social support, and more.
The researchers used machine learning to find patterns linking the stomach-brain coupling strength to mental health profiles. They checked that the results weren’t explained by heart or breathing rhythms, brain connectivity alone, baseline stomach activity, or demographic factors like age and gender.
There was a clear link between stomach-brain coupling and mental health. Somewhat counterintuitively, stronger stomach-brain coupling in fronto-parietal brain regions (areas involved in attention and cognitive control) was associated with worse mental health, such as higher anxiety, depression, stress, and fatigue. Weaker coupling in these regions was linked to better mental health, greater well-being and quality of life.
“Intuitively, we assume stronger body-brain communication is a sign of health,” said Micah Allen, senior author on the study and professor at CFIN. “But here, unusually strong stomach-brain coupling seems linked to greater psychological burden – perhaps a system under strain.”
There are some limitations to the study. Importantly, the study shows an association, not cause-and-effect. It’s unclear whether stronger stomach-brain coupling causes poor mental health, or vice versa. Additionally, participants were skewed toward young adults, so findings may not generalize to older populations. A higher-than-usual number of EGG recordings were also excluded for quality reasons, although the authors confirmed this didn’t bias results. And, the study looked at symptoms across individuals rather than formally diagnosed disorders.
The researchers suggest that, based on their findings, more research should be done in this area.
“This part of the gut has been largely ignored,” Banellis said. “Most research focuses on the microbiome and lower digestive system. Our results suggest stomach rhythms are also deeply tied to emotional well-being.”
If future research confirms a causal role, therapies could aim to modify stomach-brain coupling, possibly using non-invasive vagus nerve stimulation, medications, or mechanical interventions. The study supports the idea that mental health involves the whole body, not just the brain, and that understanding someone’s stomach-brain activity could help tailor mental health interventions.
The study was published in the journal Nature Mental Health.
Source: Aarhus University
