Potential of Probiotics as an Adjunct for Patients with Major Depressive Disorder.

Major depressive disorder (MDD) is an enfeebling disease with a lifetime incidence of 20%. While accumulating studies implicate a correlation between the disease and gut microbiota, data show that not every patient responded to probiotic treatments. To comprehensively assess the potential role of probiotics in MDD, this study first summarizes the current pathological hypothesis of the disease from a life-stage perspective, focuses on the potential role of "depression gut microbiota." Currently available managements are then briefly summarized and novel bio-materials having potential therapeutic effects on MDD are also evaluated. To harness the positive effect of probiotics, prebiotics, and postbiotics, clinical evidence and their applications on MDD patients are listed. Factors that may counteract the pre/probiotic applications, such as diet, physiology, gender difference, and use of antibiotics and antidepressants are also discussed. The endocannabinoid (eCBs) system may be promising targets for probiotic therapy. More evidence is needed to demonstrate the hierarchical factors in the complex network driving the disease, and probiotic can be one promising adjunct for patients with MDD.