Meta-analysis of the gut-brain axis and mental disorder

The gut-brain axis refers to the bidirectional information communication network between the brain and the gut. Microbiome and gut-brain axis have been implicated in mental disorders and have become the focus of neuroscience research. A meta-analysis was conducted to summarize the evidence regarding this link. A filtering search was performed using Hollis, PubMed, and Google Scholar to identify considered studies and trials. A keyword search identified 5500 articles. Seven provided analytically valuable and eligible data and were finally included for consideration and analysis. The data offered relevant studies on depression or anxiety, Schizophrenia, and Alzheimer's disease. Of the seven papers, four used correlational analysis (n=952) on depression and anxiety, two (n=384) on Schizophrenia, and one (n=80) on Alzheimers disease. These correlation analyses were designed to investigate the differences in gut microbial abundance between normal individuals and patients with mental disorders. In addition, three studies (n=314) identified a causal link by comparing the changes in mental health status by altering or influencing the gut microbiota. These causal analyses aimed to explore the differences in gut microbial abundance before and after the onset of mental disorders. In this case, mental illnesses were 2.8 to 14 times higher in the experimental groups than in the control groups. The findings support the hypothesis that the health of the gut-brain axis (microbial abundance) is inversely correlated to the incidence of many psychological disorders. However, how the gut-brain axis facilitates the pathogenesis of mental disorders remains to be further studied.