Antibiotics are some of the most commonly used medicines in the world. They are very effective at treating bacterial infections and have saved countless lives. But when used too often or without real need, antibiotics can cause harm.
One of the main concerns is their effect on the gut microbiota—the millions of bacteria and other tiny organisms that live in our intestines and help us digest food and stay healthy.
These gut bacteria don’t just affect digestion. They also send signals to the brain through a system called the gut-brain axis. Some of these bacteria help control inflammation and support brain health. When antibiotics kill off helpful bacteria, it may disturb this connection and affect mental health.
Researchers from the First Affiliated Hospital of Chongqing Medical University in China recently studied how antibiotics might increase the risk of anxiety. Their findings, published in the journal Molecular Psychiatry, suggest that antibiotics can damage mood-regulating gut bacteria, leading to higher levels of anxiety.
The study involved experiments on both mice and humans. In the first part, the researchers gave antibiotics to adult mice and then compared their behavior to mice that didn’t get any antibiotics.
The mice that took antibiotics showed more signs of anxiety, such as acting nervous or avoiding open spaces. Tests on their feces showed big changes in their gut bacteria. Two groups of bacteria, called Firmicutes and Bacteroidota, were especially affected.
These mice also had lower levels of short-chain fatty acids, which are good for gut health, and a brain chemical called acetylcholine. Acetylcholine is important for memory and mood. It helps nerve cells communicate with each other. In the mice that received antibiotics, acetylcholine levels dropped not only in the gut but also in the brain.
Next, the researchers looked at humans. They studied three groups of people: one group had recently taken antibiotics, one had not taken antibiotics, and the third group was made up of healthy people. They collected stool and blood samples and asked each person how anxious they felt.
The results were similar to the mouse study. People who had taken antibiotics were more likely to report symptoms of anxiety. They also had lower levels of acetylcholine and different gut bacteria compared to the other two groups.
A closer look showed that certain types of Bacteroides bacteria, which are helpful to the gut and brain, were missing in people and mice who had taken antibiotics. The lower levels of these bacteria were linked to the drop in acetylcholine and the increase in anxiety.
The researchers also tested a possible solution. They gave an acetylcholine-like substance called methacholine to the anxious mice. It worked. The mice became less anxious, and their brains showed fewer signs of stress.
These findings suggest that taking antibiotics too often might not just affect digestion—it could also affect how we feel emotionally. Losing important gut bacteria may lower the levels of brain chemicals that help us stay calm and balanced.
The study opens the door to new ideas for how to treat anxiety caused by antibiotics. In the future, doctors might use probiotics, diet changes, or supplements like acetylcholine to help restore gut health after antibiotic use.
In short, while antibiotics are important and often life-saving, they should be used carefully. Overusing them might harm not just the body, but also the mind.
If you care about gut health, please read studies about how junk food harms your gut health, and how probiotics can protect gut health.
For more information about health, please see recent studies about how fiber affects weight loss and your overall health, and results showing why a glass of red wine is good for your gut.
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