Probiotics—often thought of as simply gut-friendly bacteria—may also play a powerful role in improving emotional well-being.
New research using daily mood reports revealed that taking probiotics for just a few weeks significantly reduced negative feelings like stress, anxiety, and fatigue.
Probiotics May Help Ease Negative Emotions
Taking probiotics may help reduce negative emotions, according to new research by Katerina Johnson and Laura Steenbergen, published in npj Mental Health Research. The study also explored which individuals are most likely to benefit from these so-called “good” bacteria.
Probiotics are beneficial bacteria available in supplement form—such as tablets or drinks—and are also found in fermented foods like yogurt, cheese, and sauerkraut. While they’re well-known for supporting digestive health, there’s growing interest in their potential impact on mental health as well.
“The gut–brain connection provides various routes through which bacteria in the gut can influence how we feel and behave, including via the vagus nerve, immune system, and hormones,” says Johnson.
Daily Mood Reports Reveal Subtle Changes
Although animal studies have shown promising effects of probiotics on brain function and behavior, human results have been mixed. To get a clearer picture, Johnson and Steenbergen combined multiple research methods to examine how probiotics might affect emotional regulation. These included psychological surveys, daily mood tracking, and computer-based tests that measure how people process emotional information. The study involved healthy young adults who took a daily probiotic containing strains such as Lactobacillus and Bifidobacterium for one month.
This is the first study to use daily mood reports to assess the effects of probiotics. It clearly shows that probiotics can reduce negative feelings compared to a placebo. This could mean a reduction in feelings such as anxiety, stress, fatigue, or depressive tendencies. “It is striking that by simply asking participants how they were feeling each day, we could detect the beneficial effects of probiotics on mood,” says Steenbergen. “In contrast, the standard psychological questionnaires that are common in this field were not sensitive enough to pick up these changes.”
Not a Replacement for Antidepressants
The researchers found that it took about two weeks for the probiotics to improve negative feelings. It takes about the same amount of time for antidepressants to work, but whereas antidepressants tend to reduce both negative and positive mood, the results showed that the probiotics only reduced negative mood. This could be a possible benefit, although the researchers stress that probiotics should not be considered a substitute for antidepressants.
Risk-Averse People May Benefit More from Probiotics
When the researchers observed the decrease in negative feelings, they were keen to explore whether they could predict who would benefit most from probiotics. “We found that various traits, most notably a propensity for risk avoidance, were associated with a greater effect of probiotics on mood,” says Johnson.
In addition, the researchers found evidence that probiotics may affect the way participants process emotional cues. The participants who received probiotics were slightly more accurate at recognising facial expressions.
A Hopeful Future for Mood-Boosting Microbes
Many questions remain unanswered about how exactly probiotics work and their long-term effects. “Perhaps in the future probiotics could be used in a targeted way as an early intervention to reduce the chances of negative feelings progressing to mental health conditions such as depression, though more research would be needed to confirm that,” says Steenbergen.
Johnson and Steenbergen hope their findings will also spur other mental health researchers to include simple daily measures of mood in their studies. As they conclude in their paper, “In an attempt to delineate the complexity of the human brain and emotion, we cannot lose sight of asking the obvious. Sometimes the most simple questions reveal the most meaningful answers.”
Reference: “Probiotics reduce negative mood over time: the value of daily self-reports in detecting effects” by Katerina V.-A. Johnson, and Laura Steenbergen, 9 April 2025, npj Mental Health Research.
DOI: 10.1038/s44184-025-00123-z
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7 Comments
What took so long!
I could have used this information years ago.
Probiotics is a general term, like Arthritis or Cardiology Medicine. Just saying they work is poor journalism. There are hundreds of different probiotics delivered in capsules, liquids, etc. Some need to be refrigerated, or they will lose potency. The statement in the article, “The study involved healthy young adults who took a daily probiotic containing strains such as Lactobacillus and Bifidobacterium for one month,” is false; the packets in the study have nearly eight different probiotics in each packet. Which probiotic caused the difference, which were detrimental, and which prevented others from working in the gut? Nothing is mentioned about how one could even purchase such a product or use it in a medical practice. Poorly written article, study not much better.
“Which probiotic caused the difference, which were detrimental, and which prevented others from working in the gut?” The study wasn’t intended to answer these question, nor are the results intended to be consumed by the general public and immediately put into practice. If you want to benefit from research of this nature, consider finding a good naturopath in your area.
This article is basically useless because the exact strains of probiotics are not specified. Between Lactobacillus and Bifidobacterium, there are over 200 bacteria species. Which ones do we take?? Good grief. How a person can write an article like this and leave out such crucial information is beyond me.
You definitely sound like someone who could use stress relief! This article reports the results of a scientific experiment, it’s not yet medical advice that is broadly applicable to the general public.
Be sure to read the primary source (the original study).
“Following the pre-intervention testing, participants assigned to the probiotics condition were provided with 30 sachets (one for each day of intervention plus two reserves) containing 2 g (2.5 × 109 colony forming units (CFU) per gram) freeze-dried powder of the probiotic mixture Ecologic® Barrier (Winclove Probiotics B.V.). This mixture contains nine bacterial strains: Bifidobacterium bifidum W23, B. lactis W51 and W52, Lactobacillus acidophilus W37, Levilactobacillus brevis W63 (formerly classified as Lactobacillus brevis W63), Lacticaseibacillus casei W56 (formerly classified as Lactobacillus casei W56), Ligilactobacillus salivarius W24 (formerly classified as Lactobacillus salivarius W24) and Lactococcus lactis W19 and W58.”
You mean if I have a cup of Ginger tea with Probiotics in them, I can relieve some of the anxiety I been dealing with??