Recent research suggests that the bacteria that naturally populate the human gut may play an extensive role not just in a person's physical health, but also in their mental well-being. One study drew a link between certain groups of bacteria and a higher risk of mental health conditions, including depression. Another suggested that our gut bacteria may influence certain brain mechanisms and contribute to anxiety.

Now, researchers from the Shanghai Mental Health Center at Shanghai Jiao Tong University School of Medicine in China have evaluated the evidence of 21 studies — involving 1,503 participants in all — that looked at different interventions set to regulate the intestinal microbiota and whether they had any effect on symptoms of anxiety. Among the researchers were Beibei Yang, Jinbao Wei, Peijun Ju, and Jinghong Chen. The findings, which appeared yesterday in the journal General Psychiatry, emphasize the idea that scientists should not ignore the possible role of the intestinal flora when providing solutions for mental health. In the introduction to their study paper, the researchers explain that although studies in mice have suggested that interventions that regulate the balance of intestinal bacterial populations can be helpful in reducing behaviors consistent with a state of anxiety, there is currently no scientific consensus regarding the effectiveness of these interventions.

Through their review and meta-analysis, the scientists hope to get closer to some of the answers sought by those interested in the relationship between the gut and the brain.