BDNF and depressive disorder: It is well‐known that some probiotics, strains like Bifidobacterium adolescentis and Lactobacillus reuteri, hold promise in averting anxiety/depression via inhibiting infiltration of Iba1+ and LPS+/CD11b + cells (activated microglia) into the hippocampus and inducing hippocampal BDNF expression (Jang et al., 2019).