The plethora of microbes living in the human gut not only affect people’s physical health, they may also influence mental health, according to a growing body of research.
Recent studies in animals show that changes in the gut bacteria community appear to make mice less anxious, and also affect levels of the stress hormone cortisol.
In humans, there is some very early evidence of a link between gut bacteria and mental health. A new study from England found that supplements that boost “good” bacteria in the gut (called “prebiotics”) may alter the way people process emotional information, suggesting that changes in gut bacteria may have anti-anxiety effects.
Scientists are now interested in studying whether probiotics (strains of good bacteria) or prebiotics (carbohydrates that serve as food for those bacteria) could be used to treat anxiety or depression, or if the substances improve patients’ response to psychiatric drugs, said study author Philip Burnet, a researcher in the University of Oxford’s department of psychiatry.
But experts caution that the idea that taking a probiotic or a prebiotic could improve mental health in humans is still an unproven hypothesis that needs to be investigated with further research.
“It’s becoming a very interesting question in the field,” said Dr. Roger McIntyre, a professor of psychiatry and pharmacology at the University of Toronto. “The animal data looks really interesting, and looks very suggestive, [but] we’re still waiting for that convincing human study,” McIntyre said.
Could bacteria reduce anxiety?
In the new study from England, 45 healthy people ages 18 to 45 took either a prebiotic or a placebo, every day for three weeks. At the end of the study, they completed several computer tests to assess how they processed emotional information, such as negative and positive words.
During one computer test, people who took the prebiotic paid less attention to negative information, and more attention to positive information, compared with people who took a placebo. A similar effect has been seen in people who take drugs for depression or anxiety, and the finding suggests that the people in the prebiotic group had “less anxiety about negative or threatening stimuli,” Burnet said.
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