Mood disorders, like depression, used to be related only to the Central Nervous System.
Today, depression is not only considered a mental health problem but a multifactorial disorder.
The current knowledge shows that there is a gut-brain communication. This communication is bidirectional, involving the Central Nervous System, Autonomic Nervous System, neuroendocrine connections, immunological systems, and intestinal flora.
Not only commercials link constipation to worries?
It has long been known that neurons in the gastrointestinal tract also use the neurotransmitter serotonin. A study conducted on mice shows that a lack of serotonin in neurons of the intestine can cause constipation, just as the lack of serotonin in the brain can lead to depression. That could be one reason some scientists talk about “gut feelings” or “second brain”.
The gastrointestinal tract, together with the gut-associated lymphoid tissue, represents the largest lymphoid organ in the human body.
Gut can be also a major source of antigenic material. Increased gut permeability and activation of the immune-inflammatory response have critical effects on brain function and mental health.
It has been showed that changes in intestinal flora are favored by stress. The stress response acts on the immune system, causing a decrease in microbial diversity.
Changes in gut flora lead to bacterial production of various substances that stimulate the enteric nervous system, contributing to additional activation of stress response. These substances are associated with increased gut permeability, the “leaky gut phenomenon”, a phenomenon that exposes certain substances into the blood flow.
Are mental disorders gut disorders?
Of course not, but some novel findings are leading researchers to focus on new targets.
1) An increasing body of evidence shows that children with Autism Spectrum Disorder have altered gut microbiota.
2) Some other studies suggest that low flora diversity promotes inflammation (an unrecognized underlying factor in Bipolar Disorder).
3) Bacterial translocation and deficits in the compensatory immune system may cause negative symptoms and cognitive impairment in schizophrenia.
4) Current findings show an association between microbiome and gut-brain hormones with cognitive processes in schizophrenia and other mood disorders.
5) The gut microbiome has also been associated with insomnia. However, available data in this area remains limited and related scientific work has only begun.
6) In terms of sleep, patterns of diurnal activity differ from person to person, with early risers and late sleepers “chronotypes”. When investigated, chronotypes are associated with differential gut microbiome composition. A unique signature was associated with each chronotype involving two bacterial genera: Alistipes, increased in larks, and Lachnospira increased in owls.
7) Associations between gut microbiome and mood disorders in obese patients were shown. The fecal gut microbiota showed, in subjects with elevated negative mood, increased levels of Coprococcus and decreased levels of Sutterella and Lactobacillus.
The gut microbiota can have a negative impact on overall mental health. Chemicals secreted by these bacteria can play an important role in anti-inflammatory responses and contribute to the relief of psychiatric symptoms.
Treatment of schizophrenic and bipolar patients with probiotics eased symptoms, autistic children were benefited from probiotic treatment, and OCD-like behaviors were controlled.
The effects of gut structure alterations on depression, stress, and anxiety remain to be studied in depth. How gut microbiota controls cognitive behavior, mood, and neuropsychiatric disorders is still limited.
Although preclinical and clinical studies have shown that treatment with probiotics can improve mood, extensive controlled clinical trials need to be conducted to evaluate efficacy in treating mental disorders.
The interactions between drugs used in treatment and the gut microbiota need to be studied in more detail. Identification of changes in the gut microbiome associated with mental disorders may provide valuable information for treatment choices.
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