Psychobiotics: The Potential Therapeutic Promise of Microbes in Psychiatry

The recognition of the importance of human microbiome for health and disease is a relatively recent issue. Studies suggest that the microbiome may contribute to the regulation of multiple neurochemical pathways that interconnect the gastrointestinal tract and other organs with the central nervous system. The microorganisms play a vital role in the immunological development of the host. Therefore, a selection between beneficial and harmful microbes is needed, and this vital role is guided by the immune system of the host. Probiotic therapy is the application of potentially beneficial microorganisms to support the balance of beneficial and harmful microbiota in our body system. The probiotic microorganisms not only compete with the pathogens of the host but also improve the immunological state of the host. As they colonize in the human intestine, they intricately involve with different systems of the body. Organisms used as probiotics are bacteria that exist naturally in the gut and are most frequently of the Lactobacillus, Bifidobacterium, Enterococcus, and Pediococcus species. The concept of modulating the microbiome is a novel and promising idea in various areas of medicine. “Vaginal seeding” is one of the most popular issues in the press, related to modulation of the microbiome. The term “vaginal seeding” describes the use of a gauze swab to transfer maternal vaginal fluid, and hence vaginal microbiota, on to an infant born by caesarean section. The composition of the early microbiota of infants is heavily influenced by mode of delivery. In infants born by caesarean section, the microbiota resembles that of maternal skin, while in vaginally born infants it is similar to that of the maternal vagina. These early differences in the microbiota have been suggested to determine susceptibility to some common diseases. In theory, vaginal seeding might rebuild the microbiota of infants born by caesarean section to a more “natural” state and decrease the risk of disease. Strong evidence supports a therapeutic role for probiotics in the treatment of inflammatory bowel disease, irritable bowel syndrome, atopic dermatitis, and arthritis. Probiotics have immunomodulatory, hypocholesterolemic, antihypertensive, and anti-allergic properties. They are proclaimed to lighten postmenopausal symptoms and have an effect of protection toward lung emphysema. While probiotics have been suggested as an adjuvant therapy for depression, our knowledge is limited about the potency of probiotic treatments to modulate CNS function.