Gut microbes in neurocognitive and mental health disorders

Abstract

Introduction: As individuals age, the prevalence of neurocognitive and mental health disorders increases. Current biomedical treatments do not completely address the management of these conditions. Despite new pharmacological therapy the challenges of managing these diseases remain.There is increasing evidence that the Gut Microbiome (GM) and microbial dysbiosis contribute to some of the more prevalent mental health and neurocognitive disorders, such as depression, anxiety, obsessive-compulsive disorder (OCD), post-traumatic stress disorder (PTSD), schizophrenia, bipolar disorder (BP), and dementia as well as the behavioural and psychological symptoms of dementia (BPSD) through the microbiota-gut-brain axis. Methodology: Scoping review about the effect of gut microbiota on neurocognitive and mental health disorders.

Results: This scoping review found there is an evolving evidence of the involvement of the gut microbiota in the pathophysiology of neurocognitive and mental health disorders. This manuscript also discusses how the psychotropics used to treat these conditions may have an antimicrobial effect on GM, and the potential for new strategies of management with probiotics and faecal transplantation.

Conclusions: This understanding can open up the need for a gut related approach in these disorders as well as unlock the door for the role of gut related microbiota management. KEY MESSAGES Challenges of managing mental health conditions remain in spite of new pharmacological therapy. Gut dysbiosis is seen in various mental health conditions. Various psychotropic medications can have an influence on the gut microbiota by their antimicrobial effect.

Keywords: Gut microbiota; antimicrobial activity; mental health.

Figure 1.

The Brain-Gut-Microbiome Axis. Depiction of the bidirectional (two-way) communication between the brain and gut through the vagus nerve (A) and the immune system. Communication is achieved through various mechanisms including microbial by-products, such as SCFA, LPS and peptidoglycans (B), release of neurotransmitters (GABA, Norepinephrine, Serotonin, Acetylcholine, and others) and endocrine messengers via the enteroendocrine cells (C) as well as chemokine and cytokine release that can lead to neuroinflammation (D). Stress can influence the microbiota causing dysbiosis leading to an alteration of the immune system, SCFA and tryptophan levels, increasing gut permeability (“Leaky gut) (E) and activation of the HPA axis (F). Adrenocorticotropic hormone (ACTH), Cortisol Releasing Hormone (CRH), Enteroendocrine cells (EEC), y-aminobutyric acid (GABA), Lipopolysaccharides (LPS), Neurotransmitters (NT), Short Chain Fatty Acids (SCFA).