Main idea: Overall, fecal microbiota transplantation of impaired microbiota resulted in enhancing psychiatric-like disturbances (mainly depression and anxiety) in recipient animals, plausibly by impairing the immune system, inflammatory and metabolic pathways, neurochemical processes, and neuro-transmission. On the other side, preclinical and clinical data suggest that reversing or mitigating dysbiosis seems a promising strategy to restore behavioral impairments or to obtain psychiatric symptom relief.
The microorganisms residing within the gastrointestinal tract, namely gut microbiota, form a dynamic population proper of each individual, mostly composed of bacteria that co-evolved symbiotically with human species. The advances of culture-independent techniques allowed the understanding of the multiple functions of the gut microbiota in human physiology and disease, the latter often recognizing a predisposing condition in an imbalanced intestinal microbial ecosystem (dysbiosis). A complex mutual interconnection between the central nervous system (CNS), the intestine, and the gut microbiota, known as the “microbiota-gut-brain axis”, has been hypothesized to play a pivotal role in maintaining central and peripheral functions, as well as mental health. Fecal microbiota transplantation (FMT) consists of transferring the fecal matter from a donor into the gastrointestinal tract of a recipient. It is used to quickly modulate the gut microbiota and induce dysbiosis. Dysbiosis with specific microbiota imbalances seems to be strongly associated with the onset of psychiatric disorders. It alters neurodevelopment, enhancing neurodegeneration, affecting behavior and mood. It has been used to study disease development or to heal dysbiotic-related mental disorders. The study focuses on the uses of fecal microbiota transplants in psychiatric disorders.