Medical researchers from Saint Petersburg State University, as part of an international scientific team, have presented a comprehensive analysis of the role of gut microbiota in the functioning of the central nervous system and its impact on psycho-emotional state, cognitive functions, and the development of serious conditions—from depression to Alzheimer’s disease and Parkinson’s disease. The study results were published in the journal Communicative & Integrative Biology.

The study of neurodegenerative diseases remains one of the most pressing challenges in modern medicine, as their underlying mechanisms are still not fully understood, while their progression leads to severe damage to the body. For instance, Alzheimer’s and Parkinson’s diseases result in irreversible loss of memory, personality, and autonomy, placing a significant burden on families and society. Currently, there are no treatments capable of stopping or curing these conditions—existing therapies are only symptomatic, alleviating their manifestations.

According to the scientists, understanding the fundamental mechanisms of neuron death is the only path toward developing effective drugs and early diagnostic tools. Without such knowledge, the spread of these diseases will continue, and their economic and social costs will keep rising.

Researchers conducted a large-scale analysis of connections within the “gut–brain axis” and identified characteristic changes in microbiota composition across a wide range of disorders, including bipolar disorder, anxiety, schizophrenia, epilepsy, autism spectrum disorders, as well as Alzheimer’s disease, Parkinson’s disease, and multiple sclerosis.

“We have proven that the community of gut bacteria is interconnected with brain function. This is important because disturbances in this community (dysbiosis) can lead to various abnormalities in the nervous system, primarily affecting the patient’s psycho-emotional state. Accordingly, many neurological and neurodegenerative diseases are also accompanied by changes in microbial balance, which should be considered in treatment, including the use of probiotic therapy,” said Grigory Berdichevsky, assistant at the Department of Fundamental Problems of Medicine and Medical Technologies at Saint Petersburg State University.

The authors suggest that the human gut–brain axis emerged during evolution to assess the quality of incoming food and to form healthy eating habits. This system relies on enteroendocrine cells in the gut, which release signaling molecules (hormones and mediators). These activate receptors that transmit signals to the brain via the vagus nerve, reinforcing beneficial dietary behaviors.

Since the gut microbiota has adapted to live within the human body over millions of years, its members—such as bacteria—have learned to integrate into this axis. The human body, in turn, has adapted to their influence. Therefore, disruptions in this relationship can negatively affect the nervous system.

Thus, the brain does not function in isolation. Its health is closely linked to the overall health of the body, particularly the gut. This highlights the importance of microbiota diagnostics in clinical practice. Moreover, the findings may contribute to the development of new therapeutic approaches for neurological and neurodegenerative diseases. Researchers suggest that the rising prevalence of such conditions may, in part, be linked to poor diet and imbalances in gut microbiota composition.