Modulation of the Gut Microbiota by Prebiotics, Probiotics, and Psychobiotics and Its Impact on the Gut Microbiota–Brain Axis: A Systematic Review

Abstract

Simple Summary The gut microbiota–brain axis is a highly integrated bidirectional communication network that plays a fundamental role in maintaining central nervous system homeostasis and regulating neurological function, cognition, and behavior. However, uncertainty remains regarding the effectiveness of microbiota-targeted interventions for improving neurological outcomes through modulation of the gut microbiota. This systematic review analyzed 81 original studies (48 preclinical studies, 27 randomized clinical trials, and six non-randomized clinical intervention studies) to evaluate the effects of prebiotics, probiotics, and psychobiotics on the gut microbiota and gut–brain communication. The available evidence suggests that these interventions may alleviate symptoms of neurodegenerative diseases and mood disorders by modulating neuroendocrine, immune, and metabolic pathways implicated in neuroinflammation. Overall, this review provides a comprehensive synthesis of the therapeutic potential of prebiotics, probiotics, and psychobiotics as complementary interventions, highlighting the emerging role of psychobiotics as strain-specific therapies and the need to move beyond empirical dosing strategies toward precision microbiota-based interventions supported by high-quality clinical evidence.