Psychobiotics and the microbiota–gut–brain axis

Abstract

Emerging evidence indicates that the microbiota–gut–brain axis plays a pivotal role in regulating brain function, behavior, and neurological homeostasis. Alterations in gut microbiota composition have been implicated in the pathogenesis of various mental, neurodevelopmental, and neurodegenerative disorders, leading to growing interest in psychobiotics as a promising therapeutic strategy. Psychobiotics, including probiotics, prebiotics, synbiotics, and other microbiota-targeted interventions, may exert beneficial effects by modulating gut microbial composition and activity, thereby influencing bidirectional communication along the microbiota–gut–brain axis. The beneficial effects of psychobiotics are thought to be mediated through multiple mechanisms, including regulation of the hypothalamic–pituitary–adrenal (HPA) axis, modulation of neurotransmitter synthesis, attenuation of systemic and neuroinflammation, enhancement of intestinal barrier integrity, production of microbial metabolites such as short-chain fatty acids, and interaction with the central nervous system through neural, endocrine, and immune pathways. This systematic review summarizes current evidence regarding the therapeutic potential of psychobiotics in mental disorders, including depression, anxiety, schizophrenia, and bipolar disorder, as well as neurodegenerative disorders such as Alzheimer’s disease and Parkinson’s disease, and neurodevelopmental disorders including autism spectrum disorder and attention-deficit/hyperactivity disorder. In addition, the underlying biological mechanisms through which psychobiotics influence the microbiota–gut–brain axis are comprehensively discussed.