New research has found that the microorganisms living in the human gut may have a much deeper connection to mental health than previously known, offering new hope for improving conditions like depression and anxiety that affect millions of people around the world.
A team of scientists from the University of South Australia has found strong evidence that changes in the gut microbiome — the community of trillions of bacteria and other microbes in the digestive system — can directly influence brain chemistry and behaviour.
Their findings, published in Nature Mental Health, bring fresh insight into how the brain and gut communicate and how that connection could be used to improve mental wellbeing.
The researchers reviewed a large body of scientific studies exploring the “gut–brain axis”, which links the two organs through networks of nerves, hormones and chemical messengers. They found that the composition of gut bacteria can affect mood, stress responses and cognitive function, and that disturbances in these microbes are commonly seen in people with depression, anxiety and schizophrenia.
Evidence from animal studies showed that altering gut bacteria could change stress hormones and emotional behaviour. The review also found that when people with mental health conditions were treated with probiotics, dietary changes or faecal microbiota transplants, many experienced improvements in mood and anxiety symptoms. In addition, several psychiatric medications were found to alter the gut microbiome, further supporting the connection between gut bacteria and mental health.
Mental health conditions are among the leading causes of disability globally, affecting nearly one in seven people, or about 970 million individuals. Depression and anxiety account for a large share of this burden, yet existing medications and therapies often fail to help up to a third of patients.
The new findings suggest that studying the gut could open new paths for understanding why current treatments do not work for everyone and for developing safer, more accessible options.
Researchers said that treatments targeting the gut microbiome — such as probiotics, prebiotics and diet-based interventions — could potentially complement traditional approaches like medication and psychotherapy. Such methods are considered less invasive and could be adapted to different cultures and healthcare systems.
The study team emphasised that more research is needed to confirm how gut bacteria influence the brain over time and how lifestyle, diet and environment shape this relationship. They called for larger, more diverse studies that follow people over long periods to identify patterns and prove cause and effect.
As scientists continue to explore the link between the digestive system and the mind, the findings point to the possibility that improving gut health may one day become an important part of treating mental illness — a step towards tackling one of the world’s most urgent health challenges.
