Recent evidence has emerged regarding significant links between gut bacteria and various psychiatric disorders. But, do psychiatric disorders present with distinct or shared gut microbial alterations?
Preclinical studies have consistently demonstrated that fecal microbiota transplants from patients with a wide range of psychiatric conditions result in the development of the behavioral and physiological profile of the condition in germ-free mice. This suggests that psychiatric disorders may be associated with a distinct pattern of microbial perturbations, which may serve as a biomarker.
The current study included a total of 59 case-control studies, evaluating diversity or abundance of gut microbes in adult populations with major depressive disorder, bipolar disorder, psychosis and schizophrenia, anorexia nervosa, anxiety, obsessive compulsive disorder, posttraumatic stress disorder, or attention-deficit/hyperactivity disorder were included.
A total of 34 studies provided data and were included in alpha diversity meta-analyses. Significant decrease in microbial richness in patients compared with control participants were found. There was a small decrease in phylogenetic diversity.
Differences in beta diversity were consistently observed only for major depressive disorder and psychosis and schizophrenia. Depleted levels of Faecalibacterium and Coprococcus and enriched levels of Eggerthella were consistently shared between major depressive disorder, bipolar disorder, psychosis and schizophrenia, and anxiety, suggesting these disorders are characterized by a reduction of anti-inflammatory butyrate-producing bacteria, while pro-inflammatory genera are enriched. The confounding associations of region and medication were also evaluated.
Eggerthella is associated with gastrointestinal inflammation, while Faecalibacterium has known anti-inflammatory properties and is depleted in immune-mediated inflammatory diseases. These associations are likely mediated by short-chain fatty acid butyrate, as Faecalibacterium and Coprococcus are involved in its production, while Eggerthella has been associated with its depletion. Butyrate has a key role in maintaining mucosal integrity and reducing inflammation via macrophage function and decrease in proinflammatory cytokines, while increasing anti-inflammatory mediators.
Paradoxically, the family Lactobacillaceae and member genus Lactobacillus, strains from which are components of probiotic supplements and linked to positive health outcomes, were enriched in MDD, psychosis and schizophrenia, and bipolar disorder
This systematic review and meta-analysis found that gut microbiota perturbations were associated with a transdiagnostic pattern with a depletion of certain anti-inflammatory butyrate-producing bacteria and an enrichment of pro-inflammatory bacteria in patients with depression, bipolar disorder, schizophrenia, and anxiety.
Source: JAMA Psychiatry: doi:10.1001/jamapsychiatry.2021.2573
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