Bacteria in the gut may affect our mental well-being and could be linked to depression, said a study published in the journal Nature Microbiology on Monday. The World Health Organisation says an estimated 300 million people suffer from depression, and there are known links between a patient’s physical and mental health. Scientists in Belgium now believe that a wide range of gut bacteria can produce chemicals that significantly impact the brain, including several microorganisms linked — positively or negatively — to mental health. The experiment, known as the Flemish Gut Flora Project, examined depression data and stool samples from more than 1,000 people. People with depression had consistently low levels of bacteria — Coprococcus and Dialister — whether they took antidepressants or not. “The notion that microbial metabolites can interact with our brain — and thus behaviour and feelings — is intriguing,” said lead researcher Jeroen Raes, of KU Leuven University. Mr. Raes stressed, however, that while the study showed a link between gut bacteria and an individual’s mental well-being, that didn’t mean that one thing directly caused the other. Mr. Raes said his team’s research could pave the way for new, smarter treatments for the illness. After studying the genomes of over 500 types of gut bacteria, they found that several of them produced neuroactive compounds linked to a variety of mental processes.