Zhuang Z, Yang R, Wang W, et al. - Via a two-sample bi-directional Mendelian randomization analysis, researchers sought to demonstrate the causal associations among gut microbiota, metabolites, and neuropsychiatric disorders including Alzheimer’s disease (AD), major depressive disorder (MDD), and schizophrenia (SCZ). In this study, they identified evidence suggestive of causal relationships of Blautia with AD, of Enterobacteriaceae family, Enterobacteriales order, and Gammaproteobacteria class with SCZ, and of Bacilli class with MDD. Interestingly, they identified a potential link between several neurotransmitters, such as GABA and serotonin produced by gut microbiota, and the risks of neuropsychiatric disorders, suggesting their relevant roles in microbiota-host crosstalk in the brain function and behavior. In the other direction, our results inferred that neuropsychiatric disorders, like AD, SCZ, and MDD might change the composition of gut microbiota.