CRYSTAL CITY, VA. – Individuals with mood disorders might have an altered microbiome, but more information is needed to understand how the microorganisms that make up the microbiome affect patients’ health, an expert said at Focus on Neuropsychiatry presented by Current Psychiatry and the American Academy of Clinical Psychiatrists.
“An increased understanding of the neurobiology of the microbiome is required so that the benefit that these microorganisms serve to human health can be fully harnessed,” said Emily G. Severance, PhD, assistant professor of pediatrics at John Hopkins University, Baltimore.
Diseases that involve the microbiome include those with a single identifiable infectious agent that produces persistent inflammation, central nervous system diseases with mucosal surface involvement, and diseases with “variable response to antibiotic and anti-inflammatory agents.”
“It’s becoming clear that [the microbiome is] integral for the modulation of the central nervous system,” which occurs through neurotransmitter production, Dr. Severance said at the meeting presented by Global Academy for Medical Education.
“We have an extensive enteric nervous system that has the very same receptors that the brain does,” she said. “If you have those receptors activated in the gut or [are] having the neurotransmitters produced in the gut, and if there’s a way for those neurotransmitters to reach the brain, that’s a very powerful mechanism to illustrate the gut-brain axis.”
In addition to neuropsychiatric diseases, the microbiome also can be involved in inflammatory gastrointestinal, systemic rheumatoid and autoimmune, chronic inflammatory lung, and periodontal diseases, as well as immune-mediated skin disorders. Mood disorders in particular have evidence for dysbiosis in low-level inflammation and leaky gut pathology, which is present in patients with depression, Dr. Severance said. “All these data suggest that We can do that because gut bacteria are easily accessed and can be altered through probiotics, prebiotics, diet, and fecal transplant, and in patients, Lactobacillus and Bifidobacterium combinations may improve mood, reduce anxiety, and enhance cognitive function.”
In addition, epidemiological studies show that antibiotic exposure can be a risk factor for developing mood disorders. One recent study found that anti-infective agents, particularly antibiotics, increased the risk of schizophrenia (hazard rate ratio, 2.05; 95% confidence interval, 1.77-2.38) and affective disorders (HRR, 2.59; 95% CI, 2.31-2.89), which the researchers attributed to brain inflammation, the microbiome, and environmental factors (Acta Psychiatr Scand. 2016 Nov 21. doi: 10.1111/acps.12671). In mice, other researchers found that those that received a fecal transplant with a “depression microbiota” showed symptoms of major depressive disorder, compared with mice that received a “healthy microbiota.” Those results suggest that change in microbiota can induce mood disorders (Mol Psychiatry. 2016 Apr 12. doi: 10.1038/mp.2016.44).
The evidence for probiotics is mixed, primarily because the study population in trials are so heterogeneous, but there is evidence for its efficacy in patients with mood disorders, Dr. Severance said. Probiotics have been shown to prevent rehospitalization for patients in mania. For example, one study showed reduced rehospitalization in patients with mania (8 of 33 patients) who received probiotics, compared with placebo (24 of 33 patients). Also, probiotic use was associated with fewer days of rehospitalization (Bipolar Disord. 2018 Apr 25. doi: 10. 1111/bdi.12652).
Meanwhile, a pilot study analyzing patients with irritable bowel syndrome and mild to moderate anxiety and/or depression found use of B. longum in this population reduced depression scores, but not anxiety or irritable bowel syndrome symptoms, compared with placebo (Gastroenterology. 2017 May 5. doi: 10.1053/j.gastro.2017.05.003).
Probiotic efficacy can be variable for patients with mood disorders, but the intervention is a “relatively low-risk, potentially high reward” option for these patients, Dr. Severance said. “Clinicians should inquire about patient GI conditions and overall GI health. Dietary interventions and the use of probiotics and their limitations should be discussed as supplemental therapeutic options.”
Dr. Severance reported no relevant financial disclosures.
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