Depression and gut bacteria: what's the connection?

Depression and gut bacteria: what’s the connection?

collage showing a portrait of a pensive young black man and microscopic slides of bacteriaShare on Pinterest
Could the intestinal microbiota influence the symptoms of depression? Image design by MNT; Photograph by Klaus Vedfelt/Getty Images & Debbie Marshall via Wellcome Collection.
  • Depression is a common mental health disorder and a leading cause of disability worldwide, according to the World Health Organization (WHO).
  • To research shows that the gut microbiota may play a role in depressive disorders and that levels of depressive symptoms vary across ethnic groups.
  • Now researchers from the UK and the Netherlands have shown that 13 types of bacteria found in the gut are associated with symptoms of depression.

A new study published in Nature Communicationshows how gut bacteria may play a role in depression through the production of neurotransmitters, such as serotonin and glutamate.

Depression is a chronic feeling of sadness, emptiness, or inability to experience pleasure. The causes of depression are not yet fully understood, however, it is likely that various factors are involved, such as:

  • genetic
  • changes in neurotransmitter levels in the brain
  • environmental factors such as exposure to trauma
  • psychological and social factors.

In this study, researchers from Oxford Population Health, in collaboration with colleagues in the Netherlands, investigated the relationship between the composition and diversity of the gut microbiota with symptoms of depression.

They looked at data from 1,133 participants in the Rotterdam study. As part of their analysis, they made sure to control for lifestyle factors and medication use. For example, they only included people who were not taking antidepressants.

This was to avoid measuring changes in gut microbiota that are a consequence of depression — or medication — rather than a cause.

Various bacteria identified have shown potential involvement in how people produce neurotransmitters, especially those linked to depression such as glutamate.

The researchers then replicated and validated these results using data from another observational study, called the HELIUS study.

The results of this research could one day lead to the development of new treatments for conditions such as depression.

Dr Najaf Amin, study author and senior research associate at Oxford Population Health, highlighted the main findings of Medical News Todayclaiming that the research team has “identified 13 types of bacteria [12 genera and one family] associated with depression. »

Eggerthella, Do not tell me, Selimonasand Lachnoclostridium are found more abundantly, while Coprocococcus, Lachnospiraceae UCG001, Ruminococcus gauvreauii band, Eubacterium ventriosum, SubdoligranuleRuminococcaceae (UCG002, UCG003, UCG005), and [the] family Ruminococcaceae were less abundant in people with higher depression symptoms,” she said.

“These bacteria are known to be involved in the metabolism of certain key molecules, including glutamate and butyrate, through which these bacteria can influence depression.”

-Dr. Najaf Amine

Dr. Amin said “extensive and carefully conducted studies on the association of the gut microbiome with depression were lacking.” According to her, “[s]These studies are the first step towards understanding pathogenesis, providing biomarkers and therapeutic targets for disease.

“Since the gut microbiome is primarily determined by lifestyle factors, diet in particular, once causality is established, therapy would be as simple as dietary modification or the use of probiotics. “, she noted.

“Furthermore, depression is both an under-diagnosed and an over-diagnosed disease. A biomarker will allow an objective measurement of depression, which is currently lacking, thus improving diagnosis,” explains Dr. Amin.

New York-based anti-aging and regenerative medicine doctor, Dr. Neil Paulvin, not involved in the study, said DTM that “we know that the microbiome affects our mood”.

“The microbiome produces neurotransmitters such as granny, serotonin and norepinephrine. This is part of the future of mental health,” he added.

“We need to find the specific combination of gut bacteria that are good and bad for anxiety. For example, which bacteria can activate GABA [gamma-aminobutyric acid, a neurotransmitter] to help anxiety, which can affect serotonin to help depression, and whether faecal microbiota transplant will be a response to depression and anxiety.

– Dr. Neil Paulvin

Dr. Paulvin pointed out that “there are pills psychobiotics [probiotics that affect mood] currently in development. »

“We are now cultivating the information to develop programs in the future,” Dr. Paulvin said.

Dr. James Giordano, Pellegrino Professor of Neurology and Biochemistry at Georgetown University Medical Center, also not involved in this research, said that “this is a very well conducted study that controlled for several variables potentially interfering and, in doing so, demonstrated the role of certain gut microbiome species in providing chemical modulators known to have both direct and indirect effect on brain chemistry involved in cognitive and emotional functions.

“Namely, these species of intestines, Eggerthella and Eubacteria pot-belliedhave been shown to produce butyrate – an important precursor molecule to GABA, a brain chemical that acts in the regulatory control of glutamate,” he explained..

“In addition, these species have been shown to produce serotonin, which has direct effects on the enteric nervous system, the gut-brain axis, and in this way can affect serotonin levels and activity in the brain, which in turn are important for aspects of cognitive, emotional and behavioral functions.

“Overactivity of glutamate transmission in the brain has been shown to contribute to several features of depressive and anxiety disorders, and thus the contribution of the gut microbiome to the GABA and serotonin-mediated control of brain glutamate activity. (primarily via modulation of the vagus nerve) may be an important mechanism for maintaining mental health.

– Dr. James Giordano

“[T]he studies [also] revealed that some other gut species [bacteria] may exert disruptive effects on the gut microenvironment, enteric nervous system, gut-brain axis, brain chemistry, and expression of signs and symptoms of depressive and anxiety disorders.

Thus, the proliferation of these species, and the undergrowth or underactivity of beneficial species can produce local and systemic inflammatory states, which can disrupt the biochemical and physiological stability of the brain, and contribute to the development and exacerbation neuro-psychiatric conditions,” Dr. Giordano explained.

Dr. Amin noted that “it is possible to alter the composition of these [populations of] bacteria. This is possible through the use of prebiotics and probiotics. For example, butyrate-producing bacteria can be impaired by eating high-fiber diets, such as fresh fruits, whole grains, and vegetables.

Dr. Giordano agreed, saying DTM that “an important message to take away from the results of this study is that gut health through [the] gut microbiome stability is important for maintaining brain functions involved in thought, mood, and behavior.

“Growing knowledge about the gut microbiome and the gut-brain axis reinforces that careful use of pre- and probiotics may be helpful in maintaining gut and brain health,” he said. .

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