Page 37 - JCBP-3-3

Journal of Clinical and
Basic Psychosomatics Microbiota in psychosomatic disorders

quinolinic acid, has been implicated in neurodegenerative perpetuating a cycle of dysfunction. In IBD, stress worsens
diseases and mood disorders such as depression. 63 inflammation by impairing gut barrier function and
promoting immune dysregulation, triggering flare-ups.
2.4. Psychological conditions and their impact on In addition, stress-induced “leaky gut” allows LPS and
gut microbiota other microbial products into the bloodstream, causing
Stress, whether acute or chronic, plays a significant systemic inflammation that contributes to metabolic and
role in gut health by influencing the gut–brain axis, the neuroinflammatory disorders, such as obesity, type 2
communication system linking the CNS and the GI tract. diabetes, anxiety, and depression. 75-77
Through pathways involving hormonal changes, immune Anxiety and depression, two of the most common
activation, and alterations in gut motility and permeability, mental health disorders, are closely linked to changes in
stress disrupts gut function and microbiota composition. the gut microbiota. Individuals with these conditions often
This dynamic relationship between stress and the gut show reduced microbial diversity and a decline in beneficial
microbiota can create a vicious cycle where stress bacteria, such as Lactobacillus and Bifidobacterium, which
exacerbates microbial imbalances, leading to worsening play a role in producing neurotransmitters critical for
health outcomes. Chronic stress amplifies these effects, mood regulation. 71-75 Chronic low-grade inflammation has
contributing to various digestive and systemic problems by been implicated in the pathophysiology of both anxiety
altering gut motility, increasing gut permeability, changing and depression, as it interferes with neurotransmitter
the microbial ecosystem, or causing dysbiosis in the production and signaling, particularly serotonin, a key
inflammatory bowel. 65
regulator of mood, appetite, and sleep. 69,78 Dysbiosis
One key pathway is the activation of the HPA impacts the production and regulation of several key
axis, which leads to the release of cortisol and other neurotransmitters. As mentioned before, approximately
glucocorticoids that affect both the brain and gut. Stress 90% of the body’s serotonin is produced in the gut
66
also impacts the vagus nerve, a critical component of the and beneficial bacteria, such as Lactobacillus and
gut–brain axis, transmitting signals between the brain and Bifidobacterium help synthesize serotonin pre-cursors.
the gut. This stress response can alter gut motility, often Dysbiosis reduces serotonin and GABA levels, potentially
leading to diarrhea or constipation, as seen in conditions, contributing to symptoms of depression and anxiety.
such as IBS. In addition, stress increases gut permeability, GABA dysregulation due to stress can lead to heightened
allowing pathogens and toxins, such as LPS, to enter the anxiety and stress sensitivity, given that it is an inhibitory
bloodstream, triggering systemic inflammation linked neurotransmitter that reduces anxiety. Dopamine,
to disorders such as IBD and mental health conditions which influences motivation and pleasure, is another
such as depression. 67,68 Stress-induced dysbiosis also neurotransmitter affected by dysbiosis, as microbial
impacts neurotransmitter production, including imbalances disrupt its synthesis and signaling. The gut
71
serotonin, dopamine, and GABA, which are crucial for microbiota also influences norepinephrine levels, which
mood regulation. Furthermore, dysbiosis-induced are involved in the body’s stress response and arousal.
69
inflammation further disrupts neurotransmitter systems,
with pro-inflammatory cytokines, such as IL-6 and TNF-α 2.5. Clinical evidence of the gut–brain connection
interfering with mood regulation and contributing to Growing clinical data have shown that disruptions
neuroinflammation. in gut microbial composition, or dysbiosis, can have
Stress has been shown to reduce microbial diversity in significant effects on mental health. One landmark study
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the gut, depleting beneficial bacteria, such as Lactobacillus by Sanada et al. found significant differences in the gut
and Bifidobacterium, which are essential for maintaining microbiota of individuals with major depressive disorder
gut barrier integrity, immune modulation, and SCFA (MDD) compared to healthy controls, particularly
production. This depletion weakens the gut’s defense against the genus Corprococcus, the family Prevotellaceae, and
harmful bacteria, allowing the overgrowth of pathogenic Faecalibacterium.
species, such as those in the Proteobacteria phylum, which Patients with depression exhibited lower levels of
are associated with inflammation and disease. Reduced Bifidobacterium and Lactobacillus, beneficial bacteria
microbial diversity is a hallmark of stress-induced dysbiosis known for their role in maintaining gut barrier integrity
and is linked to increased susceptibility to infections, and producing neuroactive compounds, such as GABA.
chronic inflammation, and autoimmune disorders. 70-74 Furthermore, probiotic supplementation with these
The bidirectional nature of the gut–brain axis implies beneficial strains has shown promise in alleviating
that gut symptoms can increase anxiety and stress, depressive symptoms. A randomized controlled trial

Volume 3 Issue 3 (2025) 31 doi: 10.36922/JCBP025040008