Anxiety is a very common emotional state, the incidence of anxiety disorders in recent years has also shown an upward trend, there are currently a considerable number of patients with anxiety disorders in the clinic under the usual treatment of poor results. Recent studies have shown that the diversity and variety of gut flora is associated with anxiety and depressive behaviors.
The microbial community in the human gut is large and complex in structure, and is known as the second brain of humans. A growing body of research shows that the gut microbiome – the trillions of microbes in the gut – plays an important role in the immune system and metabolism by providing essential mediators of inflammation, nutrients and vitamins. In addition, the gut microbiome can affect brain function and behavior through the microbiota-gut-brain axis[1].
The human genome is made up of about 25,000 genomes, but the microbiota in the gut expresses about 3 million different genes. These genes help build molecules that help us digest food, stop the proliferation of harmful microbes, and can even help us feel emotions. Bacteria in the gut produce about 90% of Serotonin, which regulates mood and promotes health. In 2009, when researchers sampled and sequenced gut bacteria from over-stressed mice, they found that over-stressed animals and animals more likely to have mental health problems had fewer types of gut microbes or microbiomes [1].
Over the past decade or so, more and more labs have discovered that gut bacteria produce large numbers of compounds that can affect the human brain. For example, some bacteria in the genus Clostridium produce propionic acid, which improves inflammation and produces dopamine and serotonin, which regulate mood. Microbes like Bifidobacterium increase the production of butyrate, an anti-inflammatory substance that prevents intestinal toxins from entering the brain. Given an overly stressed mouse regularly fed bifidobacterium gut microbes for five weeks, the mice will be more flexible and active than before, and more willing to interact and explore [2].
Multiple innovative studies since 2016 have shown that fecal transplantation can affect emotional behavior. Fecal transplantation has been applied to some intestinal diseases and psychiatric disorders, including irritable bowel syndrome and autism, and most studies have shown that patients' symptoms have improved [3]. In one study, when mice transplanted feces from other healthy mice, their behavior remained the same. But when the mice received fecal transplants from patients with signs of anxiety and depression, the mice began to show signs of mood disorders. After the over-stressed mice received a fecal transplant from a non-stress animal, their mood was greatly relieved [2].
It can be seen that the intestinal flora can regulate our central and peripheral nervous systems by influencing a variety of factors such as neuroendocrine, stress pathways, and cytokines, thus affecting the occurrence and development of anxiety, depressive states and related behaviors. In the future, with more research on intestinal flora, anxiety disorders and depression, it will be more conducive to the diagnosis and treatment of these psychological diseases.
Zhang Yi, Zhao Yingying, Zhao Jingjie, et al. Research advances on the effects of intestinal flora on anxiety and depression. Journal of Clinical and Experimental Medicine, 2018, 17: 3
[2] Yang B, Wei J, Ju P, et al. Effects of regulating intestinal microbiota on anxiety symptoms: A systematic review. General psychiatry, 2019, 32:
Meng Danli, Guo Xianwen, Liang Liexin. Research progress on the relationship between intestinal microbiota and anxiety and depression. Journal of Clinical Gastroenterology, 2018, 30: 4