- Scientists have discovered a direct link between gut microbes and anxiety-related behaviour.
- Microbial metabolites, particularly indoles, help regulate brain activity linked to fear and stress.
- This research suggests that probiotic treatments targeting the gut-brain connection could offer new solutions for anxiety management.
For years, the relationship between gut health and mental wellbeing has intrigued researchers. A new study from Duke-NUS Medical School and the National Neuroscience Institute has now uncovered compelling evidence that the microbes in our gut may play a crucial role in regulating anxiety.
The study, published in EMBO Molecular Medicine, highlights the potential for probiotic-based therapies to help manage anxiety by restoring microbial balance in the gut.
The research team investigated how microbes influence anxious behaviour by studying mice raised in a germ-free environment, meaning they were never exposed to live microbes.
These mice exhibited significantly more anxiety-related behaviour than those with a typical microbial composition.
Further analysis revealed that the heightened anxiety was linked to overactivity in the basolateral amygdala (BLA), a region of the brain responsible for processing emotions such as fear and anxiety.
The team identified a key mechanism behind this effect. In the presence of gut microbes, specialised proteins called SK2 channels act as a regulatory system, preventing neurons from becoming overly excited.
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Without exposure to microbes, these SK2 channels failed to function properly, leading to increased neuronal activity in the amygdala and, in turn, greater anxiety.
Can probiotics help reduce anxiety?
To explore whether gut bacteria could help regulate this anxiety response, researchers reintroduced live microbes into germ-free mice.
The results were striking. The neuronal overactivity in the amygdala decreased, and the SK2 channels resumed their regulatory function.
The mice showed significantly less anxiety-related behaviour, bringing them in line with those naturally exposed to microbes.
Additionally, researchers tested indoles, microbial metabolites produced by certain bacteria, to see if they could replicate this effect. When germ-free mice were given indoles, their amygdala activity returned to normal, and their anxiety levels dropped.
These findings suggest that certain gut microbes play an essential role in maintaining emotional balance, with indoles acting as a key factor in this process.
How gut microbes influence mental health
Professor Sven Pettersson, a lead author of the study, explained that this discovery reinforces the idea that gut bacteria contribute to emotional resilience.
He noted that different levels of circulating microbial metabolites in the blood may influence an individual’s sensitivity to stress and their likelihood of experiencing anxiety.
The research also draws connections to early life development.
At birth, infants are exposed to breast milk, which contains microbes that produce indoles.
This microbial exposure could play a vital role in shaping stress responses and emotional regulation later in life.
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A new treatment for anxiety?
The findings pave the way for new approaches to treating anxiety-related disorders by targeting the gut-brain axis. Scientists believe that therapies designed to restore microbial balance – such as dietary supplementation with indoles or probiotics containing indole-producing bacteria – could provide a natural alternative to traditional anxiety medications.
Professor Patrick Tan, Senior Vice-Dean for Research at Duke-NUS, highlighted the significance of these findings: “Our research underscores the deep evolutionary links between microbes, nutrition, and brain function. This has huge potential for people suffering from stress-related conditions, such as sleep disorders or those unable to tolerate standard psychiatric medications.”
The research team now hopes to explore clinical trials to determine whether indole-based probiotics or supplements can be effectively used in humans as a natural anxiety treatment.
