Abstract
The microbiome gut brain (MGB) axis consists of bidirectional routes of communication between the gut and the brain. It has emerged as a potential therapeutic target for multiple medical specialties including psychiatry. Significant numbers of preclinical trials have taken place with some transitioning to clinical studies in more recent years. Some positive results have been reported secondary to probiotic administration in both healthy populations and specific patient groups. This review aims to summarise the current understanding of the MGB axis and the preclinical and clinical findings relevant to psychiatry. Significant differences have been identified between the microbiome of patients with a diagnosis of depressive disorder and healthy controls. Similar findings have occurred in patients diagnosed with bipolar affective disorder and irritable bowel syndrome. A probiotic containing Lactobacillus acidophilus, Lactobacillus casei, and Bifidobacterium bifidum produced a clinically measurable symptom improvement in patients with depressive disorder. To date, some promising results have suggested that probiotics could play a role in the treatment of stress-related psychiatric disease. However, more well-controlled clinical trials are required to determine which clinical conditions are likely to benefit most significantly from this novel approach.
Highlights
Psychiatric illness is estimated to account for over 32 percent of years lived with disability and 13 percent of disability-adjusted life years [1]
This review aims to summarise the current understanding of the microbiome gut brain (MGB) axis within a psychiatric context, the functioning of the MGB axis, the pre-clinical and clinical results published to date and the direction of ongoing study
Serotonin is a key neurotransmitter at both ends of the gut brain axis, with the gut microbiota controlling tryptophan catabolism along the kynurenine pathway
Summary
Psychiatric illness is estimated to account for over 32 percent of years lived with disability and 13 percent of disability-adjusted life years [1]. A change in gut microbiota can produce behavioural signs of depression [17] This was shown via FMTs from depressed patients into rats with a depleted microbiome. From the possibility of alterations of the gut microbiota producing improvements in symptoms of disease, the concept of psychobiotics has emerged. GF and SPF mice trials of infection, probiotic ingestion, and FMTs have been used to research the role of the gut microbiome [13]. FMTs have resulted in the transferral of behavioural phenotypes between patients diagnosed with depression and rats with a depleted microbiome This highlights the possible role modifying the gut microbiota could play in treating psychiatric disease [14]. This review aims to summarise the current understanding of the MGB axis within a psychiatric context, the functioning of the MGB axis, the pre-clinical and clinical results published to date and the direction of ongoing study
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