Scientists have identified specific gut bacteria that are linked to the severity of depression and anxiety symptoms
A new study published in Neurology discovered that young people with major depressive disorder (MDD) did not have significant changes in their overall gut microbiome compared to healthy people. However, the study also identified some specific bacteria and functions that differed between the two groups, some of which were linked to the severity of depression and anxiety symptoms.
The gut microbiome is a complex community of bacteria and other microbes that live in the digestive tract. It can affect the brain through various pathways, such as producing chemicals that affect mood and cognition, and activating the vagus nerve, which is the connection between the gut and the brain.
Previous studies have suggested that the gut microbiome may play a role in the development and treatment of major depressive disorder (MDD), but results are inconsistent. Furthermore, only a few studies have focused on the gut microbiome in youth with major depressive disorder, who are at higher risk for developing chronic and severe depression.
Researchers from Renmin Hospital at Wuhan University in China sought to address this gap. The study team, led by Mian Mian Chen, recruited 40 young adults with MDD and 42 healthy controls from the China Comprehensive Depression Early Warning and Intervention System Project and collected stool samples from them.
Chen’s team used a laboratory technique known as metagenomic sequencing, which allows for a comprehensive, high-resolution analysis of the gut microbiome by sampling all the genes present in the samples.
Questionnaires were administered to collect data on factors that could affect the results, known as confounding factors. These factors included sex, age, body mass index, diet, alcohol and cigarette consumption, and bowel movement quality. They also controlled for other potential confounding factors, including exercise and defecation frequency.
The researchers compared the diversity, structure and function of the gut microbiome between the two groups, identifying specific bacterial types (species) and functional units (specialized groups).
They found that the total gut microbiome was not significantly different between MDD and healthy subjects, suggesting that depression does not alter the overall composition and function of the gut microbiome in young adults.
but, Sutterellaceae Bacteria decreased in the MDD group, but “the mechanism behind this decrease in MDD abundance remains unknown and requires further study.”
Chen and his colleagues also found 15 types of bacteria that differed between youth with MDD and healthy youth, mainly belonging to the groups. Clostridium, EubacteriumAnd Ruminococcus.
“We found that the species rich in healthy controls mainly belong to… Clostridium The authors explained that group XIVa, a bacteria important for the synthesis of short-chain fatty acids, benefits the human body by influencing the immune system.
Some of these bacteria were associated with symptom scale scores, e.g Sutterellaceae With anxiety, Ruminococcus With depression and Eubacterium With physical symptoms.
They also found an increase in the specialized microbial population associated with the breakdown of an amino acid, known as cysteine, in MDD. “Increased cysteine degradation in the MDD group may further influence oxidative stress and affect cellular signal transduction… by activating inflammatory and oxidative pathways and impairing neurogenesis, synaptic plasticity and neuroprotection,” Chen and colleagues noted.
Some limitations must be acknowledged. For example, the chemical stabilization of the samples meant that they could not be further analyzed using a technique called metabolomics in order to determine the metabolites and their concentrations to better understand the underlying biochemical activity. In addition, dietary preferences and education level were not well controlled, which may influence the composition of the gut microbiome.
The study, titled “Young adults with major depression show altered microbiome,” was authored by Mian-Mian Chen, Peilin Wang, Chen Hui Shih, Zhawen Ni, Xu-Qian Xu, Nan Zhang, Wei Wang, Lihua Yao, and Zhongchun Liu. .