Aim Probiotics are live microorganisms that are part of the human microbiota. The intestines are the habitat for approximately 1013-1014 microorganisms, mainly Firmicutes and Bacteroidetes. The gut microbiota is an individual characteristic for each person and can change due to many factors, including: age, diet, and health status. The gut microbiota plays a key role in the proper functioning of the brain-gut axis, thus contributing to human health and mental well-being. The aim of this study was to present the effect of probiotic use in the course of selected psychiatric disorders. Material and methods The literature review was performed using information from PubMed/Medline, ScienceDirect, and Polish Psychiatry databases that were published before 2022. Results and discussion: A factor associated with disorders such as depression, autism, Alzheimer's disease, and mental anorexia is the generalized inflammation taking place in the patient's body. Research indicates that the inflammatory response may be caused by an imbalance in the intestinal barrier and disruption of its continuity, which may result in translocation of bacteria into the blood and activation of the immune system. The use of probiotics may play a significant role in maintaining the bacterial balance in the gastrointestinal tract and the proper functioning of the gut-brain axis, which provides a link between gut function and the emotional and cognitive centers of the brain. Conclusions Probiotics may improve mental health and cognitive function, but more clinical studies are needed on the clinical significance of the effects and how they compare to current therapies.