Therapeutic Potential of the Microbiome in the Treatment of Neuropsychiatric Disorders

Abstract

The search for rational treatment of neuropsychiatric disorders began with the discovery of chlorpromazine in 1951 and continues to evolve. Day by day, new details of the intestinal microbiota–brain axis are coming to light. As the role of microbiota in the etiopathogenesis of neuropsychiatric disorders is more clearly understood, microbiota-based (or as we propose, “fecomodulation”) treatment options are increasingly discussed in the context of treatment. Although their history dates back to ancient times, the importance of psychobiotics and fecal microbiota transplantation (FMT) has only recently been recognized. Despite there being few preclinical and clinical studies, the evidence gathered to this point suggests that consideration of the microbiome in the treatment of neuropsychiatric disorders represents an area of significant therapeutic potential. It is increasingly hoped that such treatment options will be more reliable in terms of their side effects, cost, and ease of implementation. However, there remains much to be researched. Questions will be answered through germ-free animal experiments and randomized controlled trials. In this article, the therapeutic potential of microbiota-based options in the treatment of neuropsychiatric disorders is discussed in light of recent research.

Neuroinflammation, Gut-Brain Axis and Depression

“…7 The most important component of the gutbrain axis is the intestinal bacterial content, called microbiota. 14 The microbiota begins to form from the first day of birth. 7 In fact, according to some studies, the seeds of the gut microbiota are spread in the intrauterine period.…”

“…20 In brief, the gut microbiota directly affects the development and healthy functioning of the mammalian brain. 14 The leading evidence consolidating this view is that the gut microbiota composition of patients with depression is different from that of healthy individuals. The microbiota of patients with depression exhibits low-diversity dysbiosis.…”

A Gut Feeling: The Importance of the Intestinal Microbiota in Psychiatric Disorders

“…In EAE, the treatment with minocycline is protective (123)(124)(125), and several trials were done to determine the efficacy of the treatment against MS [for a review, (118)]. Different therapeutic approaches are currently being explored experimentally (126); This includes treatment with probiotics, purified microbial compounds, fecal microbiota transplantations (FMT), phage therapies, dietary changes, and dietary habits are being evaluated.…”

“…Although encouraging, the sample size is limited and larger groups are needed to be conclusive, as indicated by the authors of the study (137). Other studies reported beneficial effects of different probiotic formulations against stress (138,139), while others failed to provide positive outcomes of mental health in healthy individuals (126,140).…”

“…Prebiotics, nutritional supplements that favor the growth of proposed beneficial microbes, is now postulated as a novel mechanism to treat behavioral diseases (129). Although probiotics for the treatment of psychiatric disorders have been proposed and discussed (126,(130)(131)(132)(133)(134), few studies are sufficiently powered to assess their benefit in humans fully (126). As highlighted in the previous section, a probiotic mixture administered for 30 days to healthy volunteers in a double-blind group comparison with placebo study showed reduced psychological distress quantified by significant reductions in global severity index, somatization, depression, anger-hostility, as well as anxiety-related markers (116).…”