A new study suggests that fecal microbiota transplantation (FMT)—a procedure that introduces healthy bacteria from a donor’s stool into a patient’s gut—might help reduce symptoms of depression.
The study found that the treatment appears even more effective when delivered through colonoscopy or enema instead of capsules.
The findings come from researchers at the Jiangsu Province Hospital of Chinese Medicine, affiliated with Nanjing University of Chinese Medicine.
Their research, published in Frontiers in Psychiatry, reviewed data from 12 clinical trials involving 681 people across several countries, including China, Australia, Canada, Finland, and the United States.
Depression affects more than 280 million people worldwide. Many people don’t fully recover with medication or therapy alone.
Scientists have recently focused on the gut–brain connection, showing that changes in the gut microbiome—the mix of bacteria and other microbes in our intestines—might influence mood and mental health.
Some conditions like irritable bowel syndrome (IBS) often occur alongside anxiety and depression. This makes gut-targeted treatments a possible way to improve both digestive and mental symptoms.
In this meta-analysis, researchers looked at clinical trials from 2019 to 2024 that tested FMT compared to a placebo or standard treatment.
The procedures varied—some used oral capsules, while others delivered the treatment directly into the gut using methods like colonoscopy, rectal enema, or endoscopic tubes. Patients were followed for different lengths of time, ranging from two weeks to one year.
Overall, the results showed that people who received FMT had greater reductions in depression symptoms than those in the control groups.
The improvements were more noticeable when the treatment was delivered directly into the intestines rather than by swallowing capsules. The strongest effects were seen in patients who also had IBS.
Benefits were seen in the short and medium term, but the long-term benefits (after six months) were not as clear. The researchers say more high-quality studies are needed to see if the effects last and how often treatment should be given.
The findings suggest that FMT could become a helpful add-on therapy for people with depression, especially those who also have IBS. While the idea of using gut bacteria to improve mood might seem unusual, this research adds to the growing evidence that the health of our gut can strongly influence how we feel mentally.
If you care about mental health, please read studies about Middle-aged women with no kids may have this mental issue and findings of scientists find a cause of mental illnesses induced by childhood abuse.
For more about mental health, please read studies about Frequent painkiller use linked to mental health risks in these people and findings of Common depression drugs may offer new treatment for bipolar disorder.
The study is published in Frontiers in Psychiatry.
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