Microbiota and psychiatric disorders: recent advances in research - Microbiota Care
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Definition of the intestine-brain axis

The gut-brain axis is a two-way communication system between the gut microbiota and the brain, involving complex interactions between the enteric nervous system (the 'second brain' located in the gut) and the central nervous system. This close link influences many aspects of our health, including our mental well-being. The communication pathways between these two systems include neural, hormonal and immune signals.

The importance of intestinal microbiota

The intestinal microbiota is made up of a multitude of bacterial species that coexist in symbiosis with their host. These bacteria play an essential role in digesting food, synthesising vitamins and protecting against infection. More and more studies are showing that the intestinal microbiota can also influence our moods, emotions and behaviour via the gut-brain axis.

Links between dysbiosis of the intestinal microbiota and mental pathologies

Recent studies have revealed significant links between the composition of the intestinal microbiota and various mental pathologies such as :

  • Depression
  • Anxiety
  • Alcohol addiction
  • Autism spectrum disorders (ASD)
  • Schizophrenia
  • Post-traumatic stress disorder (PTSD)
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Microbiota dysbiosis, characterised by an imbalance in bacterial diversity, can disrupt the normal functioning of the intestine-brain axis and contribute to the development of these pathologies.

Mechanisms involved

Several mechanisms have been proposed to explain how microbiota dysbiosis could contribute to the development of these pathologies:

  1. Chronic inflammation : Alterations in the microbiota can lead to chronic inflammation that affects the intestinal barrier. This allows toxins and bacteria to enter the bloodstream and reach the brain, triggering inflammatory reactions that are harmful to nerve cells.
  2. Production of neurotransmitters : Some bacterial strains can produce neurotransmitters such as serotonin, dopamine or GABA, which directly influence the neural pathways involved in cognitive and emotional processes.
  3. Immune regulation : The intestinal microbiota plays an important role in the development and maintenance of the immune system. Dysbiosis can disrupt this regulation, leading to abnormal immune responses that also affect the brain.
  4. Hypothalamic-pituitary-adrenal (HPA) axis : Stress can upset the balance of the intestinal microbiota, leading to activation of the HPA axis and increased release of cortisol. High levels of cortisol can have deleterious effects on the brain, notably by increasing vulnerability to mental disorders.
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The concept of psychobiotics as a future therapeutic approach

Psychobiotics are probiotics specifically designed to act on mental health by positively modulating the intestinal microbiota. By promoting a bacterial composition that is beneficial to the brain, psychobiotics could offer a promising new therapeutic strategy for treating psychiatric disorders. Preclinical studies have shown beneficial effects on certain symptoms associated with these conditions, such as :

  • Reduced stress and anxiety
  • Improved mood
  • Reducing compulsive or addictive behaviour
  • Improved cognitive function (memory, learning)

Need for further clinical studies

Although the preliminary results are encouraging, more clinical studies are essential to confirm the efficacy of psychobiotics in the treatment of mental pathologies. This research will also provide a better understanding of the underlying mechanisms involved in the interaction between the intestinal microbiota and the brain, as well as identifying the specific bacterial strains that could be used as psychobiotics.

Scientific references

  • Foster JA, McVey Neufeld KA. Gut-brain axis: how the microbiome influences anxiety and depression.Trends Neurosci. 2013;36(5):305-12.
  • Kennedy PJ, Cryan JF,Dinan TGet al.Microbiome in brain function and mental health.Trends Food Sci Technol2016;57:289-301.
  • Sarkar AYB & Lehto SMet al.Psychobiotics and the manipulation of bacteria-gut-brain signals.Trends Neurosci2016;39(11):763-781.
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With these exciting advances in research into the link between the gut microbiota and psychiatric disorders, we are witnessing a promising new era in the treatment of mental illness. The growing understanding of the gut-brain axis opens the way to innovative therapeutic approaches that could significantly improve the quality of life of patients suffering from these complex conditions.

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