Assistant Health Editor
Image by Ana Luz Crespi / Stocksy
October 20, 2025
Anxiety is on the rise, affecting nearly 60 million adults in the U.S. and close to a billion people worldwide. While medications and therapy remain the primary treatments, an unexpected player in mental health is emerging: gut bacteria.
A study published in EMBO Molecular Medicine suggests that these microscopic organisms may have a direct impact on brain function—specifically, anxiety levels—by regulating neuronal activity in a key fear-processing region of the brain.
The experiment: How gut bacteria influence anxiety
Researchers from Duke-NUS Medical School and the National Neuroscience Institute of Singapore conducted a preclinical study in mice to explore the gut-brain connection. They divided the mice into two groups:
- Normal mice: These mice had a typical gut microbiome.
- Germ-free mice: Raised in completely sterile conditions, these mice had no gut bacteria.
The results were striking: The germ-free mice displayed significantly more anxious behaviors than their normal counterparts.
When placed in an open-field test—a large box with both enclosed and open areas—the germ-free mice preferred hiding along the edges instead of exploring. In an elevated zero maze test, they spent less time in open sections, further confirming their heightened anxiety.
But behavior was just the beginning. The researchers examined the mice’s brains and found that the basolateral amygdala—a region responsible for processing fear and anxiety—was hyperactive in germ-free mice.
Their brain cells were firing excessively due to impaired SK2 channels, which normally act as brakes on neuronal excitability.
The key to a calmer brain
To see if gut bacteria could restore balance, the researchers introduced indole, a compound naturally produced by gut microbes, into the germ-free mice’s diet.
Remarkably, this simple addition reversed the brain hyperactivity and reduced their anxiety-related behaviors. The treated mice became more exploratory and exhibited activity patterns similar to normal mice.
This suggests that gut bacteria play an essential role in regulating anxiety by producing biochemical signals that influence brain function. In other words, gut microbes may act as natural mood stabilizers.
A potential breakthrough in mental health
This study offers strong evidence that the gut microbiome is directly linked to anxiety-related behaviors.
While it’s still early-stage research (and in this case, done on animals), the findings open the door to potential new treatments for anxiety disorders in humans—ones that don’t rely solely on traditional medications but instead target gut health.
Dietary interventions for more support
Probiotics (live beneficial bacteria):
Certain probiotics—especially Lactobacillus and Bifidobacterium strains—may help reduce stress, anxiety, and depression.
Prebiotics (food for gut bacteria):
Prebiotics, such as dietary fiber and galacto-oligosaccharides (GOS), can promote the growth of beneficial bacteria.
A study found that GOS supplementation helped reduce anxiety symptoms3 in healthy females by increasing Bifidobacterium levels.
Synbiotics (probiotics + prebiotics):
Combining probiotics and prebiotics may offer even greater benefits.
Fermented dairy products:
Yogurt, kefir, and other fermented dairy products naturally contain probiotics.
Spices with mental health benefits:
Certain spices contain bioactive compounds that may positively impact the gut-brain axis.
Fruits & vegetables:
The takeaway
Your gut microbiome isn’t just about digestion—it plays a powerful role in brain function and mental health. Research shows that gut dysbiosis is linked to anxiety, depression, and bipolar disorder, but dietary choices can help rebalance the microbiome.
By incorporating probiotics, prebiotics, fermented foods, and anti-inflammatory spices into your diet, you may support both gut and brain health naturally.
While we still have much to learn about the gut-brain axis, one thing is clear: What you eat doesn’t affect just your body—it shapes your mind too.