Effects of Psychotropics on the Microbiome in Patients With Depression and Anxiety: Considerations in a Naturalistic Clinical Setting

Medication use is associated with distinct microbial features in anxiety and depression

This study investigated the relationship between gut microbiota and neuropsychiatric disorders (NPDs), specifically anxiety disorder (ANXD) and/or major depressive disorder (MDD), as defined by Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV or V criteria. The study also examined the influence of medication use, particularly antidepressants and/or anxiolytics, classified through the Anatomical Therapeutic Chemical (ATC) Classification System, on the gut microbiota. Both 16S rRNA gene amplicon sequencing (16S) and shallow shotgun sequencing (WGS) were performed on DNA extracted from 666 fecal samples from the Tulsa-1000 and Neurocomputational Mechanisms of Affiliation and Personality Study Center for Biomedical Research Excellence (NeuroMAP CoBRE) cohorts. The results highlight the significant influence of medication use; antidepressant use is associated with significant differences in gut microbiota beta diversity and has a larger effect size than NPD diagnosis. Next, specific microbes were associated with ANXD and MDD, highlighting their potential for non-pharmacological intervention. Finally, the study demonstrated the capability of Random Forest classifiers to predict diagnoses of NPD and medication use from microbial profiles, suggesting a promising direction for the use of gut microbiota as biomarkers for NPD. Though the effect sizes were larger in females than males, similar trends emerged for both sexes. These findings encourage future research on the gut microbiota's role in NPD and its interactions with pharmacological treatments.

IUPHAR Review: Microbiota-Gut-Brain Axis and its role in Neuropsychiatric Disorders

The human gut microbiome, composed of a vast array of microorganisms that have co-evolved with humans, is crucial for the development and function of brain systems. Research has consistently shown bidirectional communication between the gut and the brain through neuronal, endocrine, and immunological, and chemical pathways. Recent neuroscience studies have linked changes in the microbiome and microbial metabolites to various neuropsychiatric disorders such as autism, depression, anxiety, schizophrenia, eating disorders, and neurocognitive disorders. Novel metagenome-wide association studies have confirmed these microbiome variations in large samples and expanded our understanding of the interactions between human genes and the gut microbiome. The causal relationship between gut microbiota and neuropsychiatric disorders is being elucidated through the establishment of large cohort studies incorporating microbiome data and advanced statistical techniques. Ongoing animal and human studies focused on the microbiota-gut-brain axis are promising for developing new prevention and treatment strategies for neuropsychiatric conditions. The scope of these studies has broadened from microbiome-modulating therapies including prebiotics, probiotics, synbiotics and postbiotics to more extensive approaches such as fecal microbiota transplantation. Recent systematic reviews and meta-analyses have strengthened the evidence base for these innovative treatments. Despite extensive research over the past decade, many intriguing aspects still need to be elucidated regarding the role and therapeutic interventions of the microbiota-gut-brain axis in neuropsychiatric disorders.

Persister Intestinal Bacteria, Epigenetics and Major Depression

The microbiota-gut-brain axis has been proposed as a potential modulator of mood disorders such as major depression. Complex bidirectional biochemical activities in this axis have been posited to participate in adverse mood disorders. Environmental and genetic factors have dominated recent discussions on depression. The prescription of antibiotics, antidepressants, adverse negative DNA methylation reactions and a dysbiotic gut microbiome have been cited as causal for the development and progression of depression. While research continues to investigate the microbiome-gut-brain axis, this review will explore the state of persistence of gut bacteria that underpins bacterial dormancy, possibly due to adverse environmental conditions and/or pharmaceutical prescriptions. Bacterial dormancy persistence in the intestinal microbial cohort could affect the role of bacterial epigenomes and DNA methylations. DNA methylations are highly motif driven exerting significant control on bacterial phenotypes that can disrupt bacterial metabolism and neurotransmitter formation in the gut, outcomes that can support adverse mood dispositions.

Neuroinflammation-A Crucial Factor in the Pathophysiology of Depression-A Comprehensive Review

Depression is a multifactorial psychiatric condition with complex pathophysiology, increasingly linked to neuroinflammatory processes. The present review explores the role of neuroinflammation in depression, focusing on glial cell activation, cytokine signaling, blood-brain barrier dysfunction, and disruptions in neurotransmitter systems. The article highlights how inflammatory mediators influence brain regions implicated in mood regulation, such as the hippocampus, amygdala, and prefrontal cortex. The review further discusses the involvement of the hypothalamic-pituitary-adrenal (HPA) axis, oxidative stress, and the kynurenine pathway, providing mechanistic insights into how chronic inflammation may underlie emotional and cognitive symptoms of depression. The bidirectional relationship between inflammation and depressive symptoms is emphasized, along with the role of peripheral immune responses and systemic stress. By integrating molecular, cellular, and neuroendocrine perspectives, this review supports the growing field of immunopsychiatry and lays the foundation for novel diagnostic biomarkers and anti-inflammatory treatment approaches in depression. Further research in this field holds promise for developing more effective and personalized interventions for individuals suffering from depression.

Altered oral health and microbiota in drug-free patients with schizophrenia

BACKGROUND

The oral microbiota is associated with neuro-psychiatric disorders. However, there is presently inadequate comprehension regarding the correlation between schizophrenia and the oral microbiota. Moreover, patients with schizophrenia frequently exhibit poor oral health, potentially influencing research outcomes. Therefore, this study aims to investigate changes in the oral microbiota and oral health status in drug-free schizophrenia patients.

METHODS

Oral microbiota samples were collected from 50 drug-free patients with schizophrenia and 50 healthy controls (HCs). The downstream microbiota analysis was based on Illumina sequencing of the V3-V4 hypervariable region of the 16 S rRNA gene.

RESULTS

The alpha diversity of SCZ group is increased, such as the Shannon index (p < 0.001) and Simpson index (p = 0.004), while the community structure also displays variance compared to the HC group (p < 0.001). Key discriminative taxa were found in LEfSe analysis, including the phyla Fusobacteriota, Firmicutes, and Actinobacteriota. The differential taxa and microbial functions showed a strong correlation with clinical oral conditions. Further analysis demonstrated that models based on the entire oral microbiota effectively distinguished SCZ patients from HC (AUC = 0.97).

CONCLUSIONS

The significant changes in the microbiota of Drug-free SCZ patients appear to be closely associated with the poor oral environment.

Trajectories of pharmacological therapies for treatment-resistant depression: a longitudinal study

BACKGROUND

Treatment-resistant depression (TRD) in major depressive disorder (MDD) is defined as the failure of two or more antidepressants. Few studies have characterized the natural history and treatment patterns of these patients. This study aims to identify the natural history of disease and treatment trajectories for patients with TRD.

METHODS

A retrospective longitudinal study used claims data linked to electronic health records (EHRs) from January 1, 2017, to October 31, 2021. Inclusion criteria were age ≥ 18 years, ≥ 1 MDD diagnosis, no antidepressant use at baseline, and an index date within 90 days of MDD diagnosis. Exclusions included psychiatric disorders other than MDD. TRD patients were defined as receiving third-line antidepressant treatment within two years of first-line initiation. Second- and third-line antidepressant treatment was defined as a switch to or addition of a different antidepressant with an adequate dose/duration or initiation of an augmentation treatment.

RESULTS

Out of 301,821 individuals with MDD using antidepressants or augmentation medications during the study, 2,409 incident TRD patients were selected out of 50,374 meeting the criteria. The median time to TRD (time from first to third line index date) was 11.5 months, and the TRD episode duration was 10.8 months. Initial treatment was predominantly antidepressant monotherapy, declining from 91.0% in the first line to 39.4% in the third line. Combination therapy including antidepressants and augmentation medications increased over lines, reaching 55.6% in the third line. During the TRD episode, SSRIs were the most prescribed antidepressants with the longest duration of use. Cognitive-behavioral therapy was used by 53.5% of TRD patients, while other nonpharmacological therapies were rarely used. Treatment trajectories varied by age, sex, and anxiety.

CONCLUSIONS

This study identified contemporary treatment patterns in TRD patients, with combination therapy and augmentation medications increasingly used, highlighting the need for precision treatment based on individual trajectories.

Evaluating the Efficacy of Secondary Metabolites in Antibiotic-Induced Dysbiosis: A Narrative Review of Preclinical Studies

BACKGROUND/OBJECTIVES

Drug-induced dysbiosis, particularly from antibiotics, has emerged as a significant contributor to chronic diseases by disrupting gut microbiota composition and function. Plant-derived secondary metabolites, such as polysaccharides, polyphenols, alkaloids, and saponins, show potential in mitigating antibiotic-induced dysbiosis. This review aims to consolidate evidence from preclinical studies on the therapeutic effects of secondary metabolites in restoring gut microbial balance, emphasizing their mechanisms and efficacy.

METHODS

A narrative review was conducted using PubMed, Scopus, and Web of Science. Studies were selected based on specific inclusion criteria, focusing on animal models treated with secondary metabolites for antibiotic-induced dysbiosis. The search terms included "gut microbiota", "antibiotics", and "secondary metabolites". Data extraction focused on microbial alterations, metabolite-specific effects, and mechanisms of action. Relevant findings were systematically analyzed and summarized.

RESULTS

Secondary metabolites demonstrated diverse effects in mitigating the impact of dysbiosis by modulating gut microbial composition, reducing inflammation, and supporting host biological markers. Polysaccharides and polyphenols restored the Firmicutes/Bacteroidetes ratio, increased beneficial taxa such as Lactobacillus and Bifidobacterium, and suppressed pathogenic bacteria like Escherichia-Shigella. Metabolites such as triterpenoid saponins enhanced gut barrier integrity by upregulating tight junction proteins, while alkaloids reduced inflammation by modulating proinflammatory cytokines (e.g., TNF-α, IL-1β). These metabolites also improved short-chain fatty acid production, which is crucial for gut and systemic health. While antibiotic-induced dysbiosis was the primary focus, other drug classes (e.g., PPIs, metformin) require further investigation.

CONCLUSIONS

Plant-derived secondary metabolites show promise in managing antibiotic-induced dysbiosis by restoring microbial balance, reducing inflammation, and improving gut barrier function. Future research should explore their applicability to other types of drug-induced dysbiosis and validate findings in human studies to enhance clinical relevance.

Impact of antidepressants on the composition of the gut microbiome: A systematic review and meta-analysis of in vivo studies

BACKGROUND

There is a growing body of evidence suggesting that antidepressant drugs (ADs) alter the gut microbiome of persons with depressive disorders. Herein, we aim to investigate the gut microbial profile of AD-treated animal models of depression (MoD) and persons with major depressive disorder (MDD).

METHODS

We conducted a systematic review and meta-analysis investigating the gut microbiome community-level diversity and relative abundance of microbial taxa in AD-treated animal MoD and persons with MDD.

RESULTS

24 human studies (898 participants) and 48 animal studies (849 subjects) were identified. Nonsignificant differences in gut microbial richness were observed between AD-treated and nonmedicated animals and humans. Beta diversity analysis in animals shows that AD intake is linked to a distinct gut microbial profile, a result not observed in humans. Consistent depletion of the genera Faecalibacterium and Parasutterella, along with enrichment of Bifidobacterium, was observed in AD-treated persons with MDD. In AD-treated animals, AD intake was associated with depletion of Flavobacterium and Adlercreutzia, and enrichment of Parabacteroides.

LIMITATIONS

The studies in our review were heterogeneous in their participant population, dietary intake, type of ADs used, length and dosing of AD treatment, and frequency and time of fecal sample collection.

CONCLUSION

ADs are associated with some changes to the gut microbiome. Future studies should evaluate the gut microbiome profiles between depressive disorder diagnoses that may reveal potential differences and predictors of AD response, as well as new combinatorial therapeutics with agents (e.g., specific-strain probiotic adjunctive treatment) that can ameliorate micro-composition gut dysbiosis.

Gut feeling: Exploring the intertwined trilateral nexus of gut microbiota, sex hormones, and mental health

The complex interplay between the gut microbiota, sex hormones, and mental health is emerging as a pivotal factor in understanding and managing psychiatric disorders. Beyond their traditional roles, sex hormones exert profound effects on various physiological systems including the gut microbiota. Fluctuations in sex hormone levels, notably during the menstrual cycle, influence gut physiology and barrier function, shaping gut microbiota composition and immune responses. Conversely, the gut microbiota actively modulates sex hormone levels via enzymatic processes. This bidirectional relationship underscores the significance of the gut-brain axis in maintaining mental well-being. This review explores the multifaceted interactions between sex hormones, the gut microbiota, and mental health outcomes. We highlight the potential of personalized interventions in treating psychiatric disorders, particularly in vulnerable populations such as premenopausal women and individuals with depressive disorders. By elucidating these complex interactions, we aim to provide insights for future research into targeted interventions, enhancing mental health outcomes.

The bidirectional interaction between antidepressants and the gut microbiota: are there implications for treatment response?

This review synthesizes the evidence on associations between antidepressant use and gut microbiota composition and function, exploring the microbiota's possible role in modulating antidepressant treatment outcomes. Antidepressants exert an influence on measures of gut microbial diversity. The most consistently reported differences were in β-diversity between those exposed to antidepressants and those not exposed, with longitudinal studies supporting a potential causal association. Compositional alterations in antidepressant users include an increase in the Bacteroidetes phylum, Christensenellaceae family, and Bacteroides and Clostridium genera, while a decrease was found in the Firmicutes phylum, Ruminococcaceae family, and Ruminococcus genus. In addition, antidepressants attenuate gut microbial differences between depressed and healthy individuals, modulate microbial serotonin transport, and influence microbiota's metabolic functions. These include lyxose degradation, peptidoglycan maturation, membrane transport, and methylerythritol phosphate pathways, alongside gamma-aminobutyric acid metabolism. Importantly, baseline increased α-diversity and abundance of the Roseburia and Faecalibacterium genera, in the Firmicutes phylum, are associated with antidepressant response, emerging as promising biomarkers. This review highlights the potential for gut microbiota as a predictor of treatment response and emphasizes the need for further research to elucidate the mechanisms underlying antidepressant-microbiota interactions. More homogeneous studies and standardized techniques are required to confirm these initial findings.

The atypical antipsychotics lurasidone and olanzapine exert contrasting effects on the gut microbiome and metabolic function of rats

BACKGROUND AND PURPOSE

Antipsychotics such as olanzapine are associated with significant metabolic dysfunction, attributed to gut microbiome dysbiosis. A recent notion that most psychotropics are detrimental to the gut microbiome has arisen from consistent findings of metabolic adverse effects. However, unlike olanzapine, the metabolic effects of lurasidone are conflicting. Thus, this study investigates the contrasting effects of olanzapine and lurasidone on the gut microbiome to explore the hypothesis of 'gut neutrality' for lurasidone exposure.

EXPERIMENTAL APPROACH

Using Sprague-Dawley rats, the effects of olanzapine and lurasidone on the gut microbiome were explored. Faecal and blood samples were collected weekly over a 21-day period to analyse changes to the gut microbiome and related metabolic markers.

KEY RESULTS

Lurasidone triggered no significant weight gain or metabolic alterations, instead positively modulating the gut microbiome through increases in mean operational taxonomical units (OTUs) and alpha diversity. This novel finding suggests an underlying mechanism for lurasidone's metabolic inertia. In contrast, olanzapine triggered a statistically significant decrease in mean OTUs, substantial compositional variation and a depletion in short-chain fatty acid abundance. Microbiome depletion correlated with metabolic dysfunction, producing a 30% increase in weight gain, increased pro-inflammatory cytokine expression, and increased blood glycaemic and triglyceride levels.

CONCLUSION AND IMPLICATIONS

Our results challenge the notion that all antipsychotics disrupt the gut microbiome similarly and highlights the potential benefits of gut-neutral antipsychotics, such as lurasidone, in managing metabolic side effects. Further research is warranted to validate these findings in humans to guide personalised pharmacological treatment regimens for schizophrenia.

The effects of Lactobacillus plantarum PS128 in patients with major depressive disorder: an eight-week double-blind, placebo-controlled study

Major depressive disorder (MDD) is a complex mental disorder, potentially linked to the gut-microbiota-brain axis. Probiotics like Lactobacillus plantarum PS128 (PS128) may improve depressive symptoms by modulating the gut microbiota based on our previous open trial. We conducted an 8-week double-blind, placebo-controlled trial to investigate the impact of PS128 on depression severity, markers of inflammation and gut permeability, and the gut microbiota composition in 32 patients with MDD with stable antidepressant treatment but moderate symptom severity. Following the 8-week intervention, both the Hamilton Depression Rating Scale-17 score (HAMD), and Depression and Somatic Symptoms Scale (DSSS) showed a significant decrease in both groups (p<0.001). However, there was no significant difference in the change of depression severity between groups (p=0.203). Moreover, alterations in serum levels of high sensitivity C-reactive protein, interleukin-6, tumor necrosis factor-α, and intestinal fatty acid binding protein, as well as changes in the gut microbiota composition, did not exhibit significant differences before and after intervention or between the groups. In comparison to the placebo group, our study did not find significant effects of PS128 on depressive symptoms, biomarkers of inflammation and gut permeability, and the overall gut microbiota composition. Nonetheless, we observed a potential impact of PS128 on the symbiosis of specific taxa. To comprehensively understand the psychophysiological effects of PS128 in patients with MDD, further research with a larger sample size is imperative.

Changes in the Firmicutes to Bacteriodetes ratio in the gut microbiome in individuals with anorexia nervosa following inpatient treatment: A systematic review and a case series

OBJECTIVE

Anorexia nervosa has the highest mortality rate among psychiatric illnesses. Current treatments remain ineffective for a large fraction of patients. This may be due to unclear mechanisms behind its development and maintenance. Studies exploring the role of the gut microbiome have revealed inconsistent evidence of dysbiosis. This article aims to investigate changes in the gut microbiome, particularly, mean differences in the Firmicutes to Bacteroidetes ratio, in adolescent and adult individuals with anorexia nervosa following inpatient treatment.

METHODS

Longitudinal studies investigating gut microbiome composition in inpatient populations of anorexia nervosa before and after treatment were systematically reviewed. Additionally, gut microbiome compositions were characterized in three acute anorexia nervosa inpatients early after admission and after 4-12 weeks of treatment.

RESULTS

Review results indicated an increase in the Firmicutes to Bacteroidetes ratio in individuals with anorexia nervosa after treatment. These however did not match values of their healthy counterparts. In the case-series samples, the reverse occurred with samples taken 4 weeks after treatment. In the patient who provided an extra sample 12 weeks after treatment, similar results to the studies included in the review were observed. Furthermore, Firmicutes to Bacteroidetes ratio values in the case-series samples were notably higher in the two patients who had chronic anorexia nervosa.

DISCUSSION

Differences in methodologies, small sample sizes, and insufficient data limited the generalizability of the outcomes of the reviewed studies. Results suggest a potentially unique microbiome signature in individuals with chronic anorexia nervosa, which may explain different outcomes in this group of patients.

Importance of good hosting: reviewing the bi-directionality of the microbiome-gut-brain-axis

Gut microorganisms have been shown to significantly impact on central function and studies that have associated brain disorders with specific bacterial genera have advocated an anomalous gut microbiome as the pathophysiological basis of several psychiatric and neurological conditions. Thus, our knowledge of brain-to-gut-to microbiome communication in this bidirectional axis seems to have been overlooked. This review examines the known mechanisms of the microbiome-to-gut-to-brain axis, highlighting how brain-to-gut-to-microbiome signaling may be key to understanding the cause of disrupted gut microbial communities. We show that brain disorders can alter the function of the brain-to-gut-to-microbiome axis, which will in turn contribute to disease progression, while the microbiome-to gut-to brain direction presents as a more versatile therapeutic axis, since current psychotropic/neurosurgical interventions may have unwanted side effects that further cause disruption to the gut microbiome. A consideration of the brain-to-gut-to-microbiome axis is imperative to better understand how the microbiome-gut-brain axis overall is involved in brain illnesses, and how it may be utilized as a preventive and therapeutic tool.

The synergistic impact of probiotics and dietary fiber on constipation management in chlorpromazine-induced schizophrenia patients: exploring the modulation of intestinal microbiota and neurotrophic factors

OBJECTIVE

To explore the improvement effect of probiotics combined with dietary fiber on constipation in patients with schizophrenia.

METHODS

To compare the improvement scores of constipation, constipation symptoms, quality of life, neurotrophic factors-related indicators, and clinical efficacy between the two groups.

RESULTS

There was no statistically significant difference in Cleveland Constipation Scoring System (CCS) scores in the control group before and after treatment (p > 0.05), while the CCS scores in the observation group decreased significantly after treatment (p < 0.05); Patient Assessment of Constipation Symptoms scores significantly decreased in the observation group compared to the control group (p < 0.05), with no significant difference in Patient Assessment of Constipation Quality of Life scores between the two groups pre- and post-treatment; Neuron-specific enolase levels decreased significantly in both groups post-treatment, while brain-derived neurotrophic factor, neuregulin-1, and nerve growth factor levels increased significantly, with a more pronounced rise in the observation group (p < 0.05). Additionally, the total effective rate of clinical treatment in the observation group was higher than that in the control group (p < 0.05).

CONCLUSION

Probiotics combined with dietary fiber can improve constipation symptoms in patients with schizophrenia accompanied by constipation, effectively maintain the balance of intestinal microbiota, and improve the quality of life of patients. Additionally, levels of neurotrophic factors associated with bowel function and neurological health increased significantly, with a higher total effective rate of clinical treatment observed in the probiotics and dietary fiber group. These findings suggest the potential efficacy of probiotics and dietary fiber in managing constipation in this patient population.

Psycho-Pharmacomicrobiomics: A Systematic Review and Meta-Analysis

BACKGROUND

Understanding the interactions between the gut microbiome and psychotropic medications (psycho-pharmacomicrobiomics) could improve treatment stratification strategies in psychiatry. In this systematic review and meta-analysis, we first explored whether psychotropics modify the gut microbiome; second, we investigated whether the gut microbiome affects the efficacy and tolerability of psychotropics.

METHODS

Following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, we searched (November 2022) for longitudinal and cross-sectional studies that investigated the effect of psychotropics on the gut microbiome. The primary outcome was the difference in diversity metrics (alpha and beta) before and after treatment with psychotropics (longitudinal studies) and in medicated compared with unmedicated individuals (cross-sectional studies). Secondary outcomes included the association between gut microbiome and efficacy and tolerability outcomes. Random effect meta-analyses were conducted on alpha diversity metrics, while beta diversity metrics were pooled using distance data extracted from graphs. Summary statistics included standardized mean difference and Higgins I2 for alpha diversity metrics and F and R values for beta diversity metrics.

RESULTS

Nineteen studies were included in our synthesis; 12 investigated antipsychotics and 7 investigated antidepressants. Results showed significant changes in alpha (4 studies; standard mean difference: 0.12; 95% CI: 0.01-0.23; p = .04; I2: 14%) and beta (F = 15.59; R2 = 0.05; p < .001) diversity metrics following treatment with antipsychotics and antidepressants, respectively. Altered gut microbiome composition at baseline was associated with tolerability and efficacy outcomes across studies, including response to antidepressants (2 studies; alpha diversity; standard mean difference: 2.45; 95% CI: 0.50-4.40; p < .001, I2: 0%).

CONCLUSIONS

Treatment with psychotropic medications is associated with altered gut microbiome composition, and the gut microbiome may in turn influence the efficacy and tolerability of these medications.

Intestinal microbial diversity of swines fed with different sources of lithium

A drug that is widely used in the treatment of psychiatric disorder is lithium (Li) salts. The people who make therapeutic use of this drug develop a series of side effects. Through metataxonomic data, this study assessed the impacts of lithium, as Li carbonate or Li-enriched mushrooms, on the microbial composition of the ileum, colon, and feces of piglets. Employing Bray-Curtis metric, no differences were observed among the treatments evaluated. Nevertheless, the alpha diversity indices showed differences in the Simpson, Shannon, and Chao-1 indices in the colon and Chao-1 in the feces in the diets with Li compared with the diets without Li. The taxa with the highest relative abundance varied among the ileum, colon, and feces, with a predominance of the phyla Firmicutes, Bacteroidota, and Proteobacteria in diets with Li. Many groups of microorganisms that are important for the health of the host (e.g., Lactobacillus, Ruminococcaceae, Enterorhabdus, Muribaculaceae, and Coprococcus) had their relative abundance increased in animals that received diets with the recommended dose of lithium. Furthermore, there was an increase in the abundance of Prevotellaceae and Bacteroidales (in the diet with Li-enriched mushroom) and Clostridia, Ruminococcus, Burkholderia, and Bacteroidales (diets with Li carbonate) at the recommended dosages. This is the first study to show the effects of Li carbonate and Li-enriched mushrooms on the intestinal microbiota of piglets. Thus, the effects of lithium on the body may be related to its ability to change the composition of the intestinal microbiota.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-03938-3.

Medication Use is Associated with Distinct Microbial Features in Anxiety and Depression

This study investigated the relationship between gut microbiota and neuropsychiatric disorders (NPDs), specifically anxiety disorder (ANXD) and/or major depressive disorder (MDD), as defined by DSM-IV or V criteria. The study also examined the influence of medication use, particularly antidepressants and/or anxiolytics, classified through the Anatomical Therapeutic Chemical (ATC) Classification System, on the gut microbiota. Both 16S rRNA gene amplicon sequencing and shallow shotgun sequencing were performed on DNA extracted from 666 fecal samples from the Tulsa-1000 and NeuroMAP CoBRE cohorts. The results highlight the significant influence of medication use; antidepressant use is associated with significant differences in gut microbiota beta diversity and has a larger effect size than NPD diagnosis. Next, specific microbes were associated with ANXD and MDD, highlighting their potential for non-pharmacological intervention. Finally, the study demonstrated the capability of Random Forest classifiers to predict diagnoses of NPD and medication use from microbial profiles, suggesting a promising direction for the use of gut microbiota as biomarkers for NPD. The findings suggest that future research on the gut microbiota's role in NPD and its interactions with pharmacological treatments are needed.

Safety, feasibility, and impact on the gut microbiome of kefir administration in critically ill adults

BACKGROUND

Dysbiosis of the gut microbiome is frequent in the intensive care unit (ICU), potentially leading to a heightened risk of nosocomial infections. Enhancing the gut microbiome has been proposed as a strategic approach to mitigate potential adverse outcomes. While prior research on select probiotic supplements has not successfully shown to improve gut microbial diversity, fermented foods offer a promising alternative. In this open-label phase I safety and feasibility study, we examined the safety and feasibility of kefir as an initial step towards utilizing fermented foods to mitigate gut dysbiosis in critically ill patients.

METHODS

We administered kefir in escalating doses (60 mL, followed by 120 mL after 12 h, then 240 mL daily) to 54 critically ill patients with an intact gastrointestinal tract. To evaluate kefir's safety, we monitored for gastrointestinal symptoms. Feasibility was determined by whether patients received a minimum of 75% of their assigned kefir doses. To assess changes in the gut microbiome composition following kefir administration, we collected two stool samples from 13 patients: one within 72 h of admission to the ICU and another at least 72 h after the first stool sample.

RESULTS

After administering kefir, none of the 54 critically ill patients exhibited signs of kefir-related bacteremia. No side effects like bloating, vomiting, or aspiration were noted, except for diarrhea in two patients concurrently on laxatives. Out of the 393 kefir doses prescribed for all participants, 359 (91%) were successfully administered. We were able to collect an initial stool sample from 29 (54%) patients and a follow-up sample from 13 (24%) patients. Analysis of the 26 paired samples revealed no increase in gut microbial α-diversity between the two timepoints. However, there was a significant improvement in the Gut Microbiome Wellness Index (GMWI) by the second timepoint (P = 0.034, one-sided Wilcoxon signed-rank test); this finding supports our hypothesis that kefir administration can improve gut health in critically ill patients. Additionally, the known microbial species in kefir were found to exhibit varying levels of engraftment in patients' guts.

CONCLUSIONS

Providing kefir to critically ill individuals is safe and feasible. Our findings warrant a larger evaluation of kefir's safety, tolerability, and impact on gut microbiome dysbiosis in patients admitted to the ICU.

TRIAL REGISTRATION

NCT05416814; trial registered on June 13, 2022.

Intestinal metabolites predict treatment resistance of patients with depression and anxiety

BACKGROUND

The impact of the gut microbiota on neuropsychiatric disorders has gained much attention in recent years; however, comprehensive data on the relationship between the gut microbiome and its metabolites and resistance to treatment for depression and anxiety is lacking. Here, we investigated intestinal metabolites in patients with depression and anxiety disorders, and their possible roles in treatment resistance.

RESULTS

We analyzed fecal metabolites and microbiomes in 34 participants with depression and anxiety disorders. Fecal samples were obtained three times for each participant during the treatment. Propensity score matching led us to analyze data from nine treatment responders and nine non-responders, and the results were validated in the residual sample sets. Using elastic net regression analysis, we identified several metabolites, including N-ε-acetyllysine; baseline levels of the former were low in responders (AUC = 0.86; 95% confidence interval, 0.69-1). In addition, fecal levels of N-ε-acetyllysine were negatively associated with the abundance of Odoribacter. N-ε-acetyllysine levels increased as symptoms improved with treatment.

CONCLUSION

Fecal N-ε-acetyllysine levels before treatment may be a predictive biomarker of treatment-refractory depression and anxiety. Odoribacter may play a role in the homeostasis of intestinal L-lysine levels. More attention should be paid to the importance of L-lysine metabolism in those with depression and anxiety.

The human gut microbiome in critical illness: disruptions, consequences, and therapeutic frontiers

With approximately 39 trillion cells and over 20 million genes, the human gut microbiome plays an integral role in both health and disease. Modern living has brought a widespread use of processed food and beverages, antimicrobial and immunomodulatory drugs, and invasive procedures, all of which profoundly disrupt the delicate homeostasis between the host and its microbiome. Of particular interest is the human gut microbiome, which is progressively being recognized as an important contributing factor in many aspects of critical illness, from predisposition to recovery. Herein, we describe the current understanding of the adverse impacts of standard intensive care interventions on the human gut microbiome and delve into how these microbial alterations can influence patient outcomes. Additionally, we explore the potential association between the gut microbiome and post-intensive care syndrome, shedding light on a previously underappreciated avenue that may enhance patient recuperation following critical illness. There is an impending need for future epidemiological studies to encompass detailed phenotypic analyses of gut microbiome perturbations. Interventions aimed at restoring the gut microbiome represent a promising therapeutic frontier in the quest to prevent and treat critical illnesses.

Exploring the human gut microbiota targets in relation to the use of contemporary antidepressants

BACKGROUND

Antidepressants, specifically selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs), are commonly prescribed for depression treatment. Animal studies have shown that antidepressants can influence gut microbiota composition and specific bacterial taxa. We aimed to investigate the association between antidepressant use and human gut microbiota composition and functional pathway.

METHODS

We collected information on antidepressant use, demographic, food patterns, and clinical characteristics through questionnaires and medical records. The gut microbiota profiles of 271 depressive patients were carried out through 16S rRNA gene sequencing. Patients were categorized based on different types of antidepressant use groups for gut microbiota comparisons. MaAsLin2 was performed to evaluate microbiota composition across groups. PICRUSt2 was used to predict microbiota functional pathways.

RESULTS

Patients taking SSRIs or SNRIs had a lower microbiota diversity. We found seven taxa abundances (Turicibacter, Barnesiella, Lachnospiraceae_ND3007_group, Romboutia, Akkermansia, Dialister, Romboutia and Fusicatenibacter) differed in patients with various types of antidepressants compared with those without antidepressant treatments (p < 0.05). Turicibacter inversely correlated with depression severity in SSRIs or SNRI users (r = -0.43, p < 0.05). Top identified pathways were related to compound fermentation and biosynthesis in microbiota function.

CONCLUSION

Antidepressant usage, especially SSRIs and SNRIs, associates with changes in gut microbiota composition and specific taxa. Given our study's preliminary cross-sectional nature, further research is warranted to comprehend the relationship between antidepressant use, treatment response, and gut microbiota, aiming to enhance therapeutic interventions in the future.

The relationship between sleep, gut microbiota, and metabolome in patients with depression and anxiety: A secondary analysis of the observational study

BACKGROUND

Growing attention is paid to the association between alterations in the gut microbiota and their metabolites in patients with psychiatric disorders. Our study aimed to determine how gut microbiota and metabolomes are related to the sleep quality among patients with depression and anxiety disorders by analyzing the datasets of our previous study.

METHODS

Samples were collected from 40 patients (depression: 32 patients [80.0%]); anxiety disorders: 8 patients [20.0%]) in this study. Gut microbiomes were analyzed using 16S rRNA gene sequencing and gut metabolomes were analyzed by a mass spectrometry approach. Based on the Pittsburgh Sleep Quality Index (PSQI), patients were categorized into two groups: the insomnia group (PSQI score ≥ 9, n = 20) and the non-insomnia group (PSQI score < 9, n = 20).

RESULTS

The insomnia group showed a lower alpha diversity in the Chao1 and Shannon indices than the non-insomnia group after the false discovery rate (FDR) correction. The relative abundance of genus Bacteroides showed a positive correlation with PSQI scores in the non-insomnia group. The concentrations of glucosamine and N-methylglutamate were significantly higher in the insomnia group than in the non-insomnia group.

CONCLUSIONS

Our findings suggest that specific taxa could affect the sleep quality among patients with depression and anxiety disorders. Further studies are needed to elucidate the impact of sleep on specific gut microbiota and metabolomes in depression and anxiety disorders.

Alterations in the intestinal microbiota associated with active tuberculosis and latent tuberculosis infection

Objectives

To study the characteristics of intestinal microbiota at different stages of Mycobacterium tuberculosis infection.

Methods

Fecal samples of 19 active tuberculosis (ATB) patients, 21 latent tuberculosis infection (LTBI) individuals, and 20 healthy controls (HC) were collected. Gut microbiota of all the participants were analyzed by 16S rDNA sequencing. Clinical information of ATB patients was also collected and analyzed.

Results

Both ATB and LTBI groups showed significant decreases in microbial diversity and decline of Clostridia. For ATB patients, bacteria within phylum Proteobacteria increased. While for LTBI individuals, genera Prevotella and Rosburia enriched. The abundance of Faecalibacterium, Clostridia and Gammaproteobacteria has the potential to diagnose ATB, with the area under the curve (AUC) of 0.808, 0.784 and 0.717. And Prevotella and Rosburia has the potential to diagnose LTBI, with the AUC of 0.689 and 0.689. Notably, in ATB patients, the relative abundance of Blautia was negatively correlated with the proportions of peripheral T cells and CD8+T cells. And serum direct bilirubin was positively correlated with Bacteroidales, while negatively correlated with Clostridiales in ATB patients.

Conclusions

The specifically changed bacteria are promising markers for ATB and LTBI diagnosis. Some gut bacteria contribute to anti-MTB immunity through interactions with T cells and bilirubin.

Pharmacomicrobiomics of Antidepressants in Depression: A Systematic Review

This systematic review evaluated the animal and human evidence for pharmacomicrobiomics (PMx) interactions of antidepressant medications. Studies of gut microbiota effects on functional and behavioral effects of antidepressants in human and animal models were identified from PubMed up to December 2022. Risk of bias was assessed, and results are presented as a systematic review following PRISMA guidelines. A total of 28 (21 animal, 7 human) studies were included in the review. The reviewed papers converged on three themes: (1) Antidepressants can alter the composition and metabolites of gut microbiota, (2) gut microbiota can alter the bioavailability of certain antidepressants, and (3) gut microbiota may modulate the clinical or modeled mood modifying effects of antidepressants. The majority (n = 22) of studies had at least moderate levels of bias present. While strong evidence is still lacking to understand the clinical role of antidepressant PMx in human health, there is evidence for interactions among antidepressants, microbiota changes, microbiota metabolite changes, and behavior. Well-controlled studies of the mediating and moderating effects of baseline and treatment-emergent changes in microbiota on therapeutic and adverse responses to antidepressants are needed to better establish a potential role of PMx in personalizing antidepressant treatment selection and response prediction.

Comparison of gut microbiome profile in patients with schizophrenia and healthy controls - A plausible non-invasive biomarker?

The human gut microbiome regulates brain function through the microbiome-gut-brain axis and is implicated in several neuropsychiatric disorders. However, the relationship between the gut microbiome and the pathogenesis of schizophrenia (SCZ) is poorly defined, and very few studies have examined the effect of antipsychotic treatment response. We aim to study the differences in the gut microbiota among drug-naïve (DN SCZ) and risperidone-treated SCZ patients (RISP SCZ), compared to healthy controls (HCs). We recruited a total of 60 participants, from the clinical services of a large neuropsychiatric hospital, which included DN SCZ, RISP SCZ and HCs (n = 20 each). Fecal samples were analyzed using 16s rRNA sequencing in this cross-sectional study. No significant differences were found in taxa richness (alpha diversity) but microbial composition differed between SCZ patients (both DN and RISP) and HCs (PERMANOVA, p = 0.02). Linear Discriminant Analysis Effect Size (LEfSe) and Random Forest model identified the top six genera, which significantly differed in abundance between the study groups. A specific genus-level microbial panel of Ruminococcus, UCG005, Clostridium_sensu_stricto_1 and Bifidobacterium could discriminate SCZ patients from HCs with an area under the curve (AUC) of 0.79, HCs vs DN SCZ (AUC: 0.68), HCs vs RISP SCZ (AUC: 0.93) and DN SCZ vs RISP SCZ (AUC: 0.87). Our study identified distinct microbial signatures that could aid in the differentiation of DN SCZ, RISP SCZ, and HCs. Our findings contribute to a better understanding of the role of the gut microbiome in SCZ pathophysiology and suggest potential targeted interventions.

The gut microbiome in social anxiety disorder: evidence of altered composition and function

The microbiome-gut-brain axis plays a role in anxiety, the stress response and social development, and is of growing interest in neuropsychiatric conditions. The gut microbiota shows compositional alterations in a variety of psychiatric disorders including depression, generalised anxiety disorder (GAD), autism spectrum disorder (ASD) and schizophrenia but studies investigating the gut microbiome in social anxiety disorder (SAD) are very limited. Using whole-genome shotgun analysis of 49 faecal samples (31 cases and 18 sex- and age-matched controls), we analysed compositional and functional differences in the gut microbiome of patients with SAD in comparison to healthy controls. Overall microbiota composition, as measured by beta-diversity, was found to be different between the SAD and control groups and several taxonomic differences were seen at a genus- and species-level. The relative abundance of the genera Anaeromassillibacillus and Gordonibacter were elevated in SAD, while Parasuterella was enriched in healthy controls. At a species-level, Anaeromassilibacillus sp An250 was found to be more abundant in SAD patients while Parasutterella excrementihominis was higher in controls. No differences were seen in alpha diversity. In relation to functional differences, the gut metabolic module 'aspartate degradation I' was elevated in SAD patients. In conclusion, the gut microbiome of patients with SAD differs in composition and function to that of healthy controls. Larger, longitudinal studies are warranted to validate these preliminary results and explore the clinical implications of these microbiome changes.

The current state of research for psychobiotics use in the management of psychiatric disorders-A systematic literature review

The need to find new therapeutic interventions in patients diagnosed with psychiatric disorders is supported by the data suggesting high rates of relapse, chronic evolution, therapeutic resistance, or lack of adherence and disability. The use of pre-, pro-, or synbiotics as add-ons in the therapeutic management of psychiatric disorders has been explored as a new way to augment the efficacy of psychotropics and to improve the chances for these patients to reach response or remission. This systematic literature review focused on the efficacy and tolerability of psychobiotics in the main categories of psychiatric disorders and it has been conducted through the most important electronic databases and clinical trial registers, using the PRISMA 2020 guidelines. The quality of primary and secondary reports was assessed using the criteria identified by the Academy of Nutrition and Diabetics. Forty-three sources, mostly of moderate and high quality, were reviewed in detail, and data regarding the efficacy and tolerability of psychobiotics was assessed. Studies exploring the effects of psychobiotics in mood disorders, anxiety disorders, schizophrenia spectrum disorders, substance use disorders, eating disorders, attention deficit hyperactivity disorder (ADHD), neurocognitive disorders, and autism spectrum disorders (ASD) were included. The overall tolerability of the interventions assessed was good, but the evidence to support their efficacy in specific psychiatric disorders was mixed. There have been identified data in favor of probiotics for patients with mood disorders, ADHD, and ASD, and also for the association of probiotics and selenium or synbiotics in patients with neurocognitive disorders. In several domains, the research is still in an early phase of development, e.g., in substance use disorders (only three preclinical studies being found) or eating disorders (one review was identified). Although no well-defined clinical recommendation could yet be formulated for a specific product in patients with psychiatric disorders, there is encouraging evidence to support further research, especially if focused on the identification of specific sub-populations that may benefit from this intervention. Several limitations regarding the research in this field should be addressed, i.e., the majority of the finalized trials are of short duration, there is an inherent heterogeneity of the psychiatric disorders, and the diversity of the explored Philae prevents the generalizability of the results from clinical studies.

Microbiome in Anxiety and Other Psychiatric Disorders

Initial studies suggested that the fluctuations in the quantity, variety, and composition of the gut microbiota can significantly affect disease processes. This change in the gut microbiota causing negative health benefits was coined dysbiosis. Initial research focused on gastrointestinal illnesses. However, the gut microbiome was found to affect more than just gastrointestinal diseases. Numerous studies have proven that the gut microbiome can influence neuropsychiatric diseases such as Parkinson's disease, Alzheimer's disease, and multiple sclerosis.

The Potential Impact of Age on Gut Microbiota in Patients with Major Depressive Disorder: A Secondary Analysis of the Prospective Observational Study

We aimed to investigate the impact of aging on the relationship among the composition of gut microbiota, gastrointestinal (GI) symptoms, and the course of treatment for major depressive disorder (MDD) by analyzing the datasets from our previous study. Patients with MDD were recruited, and their stools were collected at three time points (baseline, midterm, and endpoint) following the usual antidepressant treatment. Gut microbiota were analyzed using 16S rRNA gene sequencing. Patients were categorized into two groups based on their age: the late-life group over 60 years and the middle-aged group under 60 years. GI symptoms were assessed with scores of item 11 of the Hamilton Anxiety Rating Scale. One hundred and ninety samples were collected from 32 patients with MDD. Several gut microbes had higher relative abundances in the late-life group than in the middle-aged group. In addition, the late-life group showed significantly higher diversity in the Chao1 index at baseline compared with the middle-aged group. We further found possible microbial taxa related to GI symptoms in patients with late-life depression. The abundance of several bacterial taxa may contribute to GI symptoms in the late-life depression, and our findings suggest that the therapeutic targets for the application of gut microbiota may differ depending on the age group of patients with depression.

Exploring the relationship between the gut microbiome and mental health outcomes in a posttraumatic stress disorder cohort relative to trauma-exposed controls

Posttraumatic stress disorder (PTSD) imposes a significant burden on patients and communities. Although the microbiome-gut-brain axis has been proposed as a mediator or moderator of PTSD risk and persistence of symptoms, clinical data directly delineating the gut microbiome's relationship to PTSD are sparse. This study investigated associations between the gut microbiome and mental health outcomes in participants with PTSD (n = 79) and trauma-exposed controls (TECs) (n = 58). Diagnoses of PTSD, major depressive disorder (MDD), and childhood trauma were made using the Clinician-Administered PTSD Scale for DSM-5 (CAPS-5), MINI International Neuropsychiatric Interview (MINI), and Childhood Trauma Questionnaire (CTQ), respectively. Microbial communities from stool samples were profiled using 16S ribosomal RNA gene V4 amplicon sequencing and tested for associations with PTSD-related variables of interest. Random forest models identified a consortium of four genera, i.e.,  a combination of Mitsuokella, Odoribacter, Catenibacterium, and Olsenella, previously associated with periodontal disease, that could distinguish PTSD status with 66.4% accuracy. The relative abundance of this consortium was higher in the PTSD group and correlated positively with CAPS-5 and CTQ scores. MDD diagnosis was also associated with increased relative abundance of the Bacteroidetes phylum. Current use of psychotropics significantly impacted community composition and the relative abundances of several taxa. Early life trauma may prime the microbiome for changes in composition that facilitate a pro-inflammatory cascade and increase the risk of development of PTSD. Future studies should rigorously stratify participants into healthy controls, TECs, and PTSD (stratified by psychotropic drug use) to explore the role of the oral-gut-microbiome-brain axis in trauma-related disorders.

A Comprehensive Review on the Role of the Gut Microbiome in Human Neurological Disorders

The human body is full of an extensive number of commensal microbes, consisting of bacteria, viruses, and fungi, collectively termed the human microbiome. The initial acquisition of microbiota occurs from both the external and maternal environments, and the vast majority of them colonize the gastrointestinal tract (GIT). These microbial communities play a central role in the maturation and development of the immune system, the central nervous system, and the GIT system and are also responsible for essential metabolic pathways. Various factors, including host genetic predisposition, environmental factors, lifestyle, diet, antibiotic or nonantibiotic drug use, etc., affect the composition of the gut microbiota. Recent publications have highlighted that an imbalance in the gut microflora, known as dysbiosis, is associated with the onset and progression of neurological disorders. Moreover, characterization of the microbiome-host cross talk pathways provides insight into novel therapeutic strategies. Novel preclinical and clinical research on interventions related to the gut microbiome for treating neurological conditions, including autism spectrum disorders, Parkinson's disease, schizophrenia, multiple sclerosis, Alzheimer's disease, epilepsy, and stroke, hold significant promise. This review aims to present a comprehensive overview of the potential involvement of the human gut microbiome in the pathogenesis of neurological disorders, with a particular emphasis on the potential of microbe-based therapies and/or diagnostic microbial biomarkers. This review also discusses the potential health benefits of the administration of probiotics, prebiotics, postbiotics, and synbiotics and fecal microbiota transplantation in neurological disorders.

Case report: Carbohydrate malabsorption in inpatients with anorexia nervosa

BACKGROUND

Gastrointestinal (GI) complaints are frequently observed in patients who suffer from anorexia nervosa (AN). These symptoms may hamper treatment and weight regain and are often perceived as the cause, not the consequence, of the disease. Since carbohydrate malabsorption also produces these symptoms, this might underly or contribute to these complaints. So far, the role of carbohydrate malabsorption (fructose malabsorption and lactose intolerance) in AN has not yet been investigated.

METHODS

For this case series, inpatients with AN of restrictive type (n = 3), purging type (n = 3), and atypical AN (n = 1) conducted hydrogen breath tests with 25 g of fructose and 50 g of lactose to investigate carbohydrate malabsorption. Results were then analyzed in association with body mass index (BMI) and patient-reported outcomes (disordered eating, body image disturbances, anxiety, depressive symptoms, perceived stress, and GI complaints).

RESULTS

Based on the hydrogen breath test results, three of the seven female patients were classified as lactose intolerant and one presented fructose malabsorption. Both hydrogen curves for fructose (r = -0.632, p < 0.001) and lactose (r = -0.704, p < 0.001) showed a negative correlation with BMI. No association was observed between hydrogen values and patient-reported outcomes.

CONCLUSION

In patients with AN, GI symptoms caused by intolerance of common monosaccharides and disaccharides may be an underestimated burden and should be considered in the diagnosis and therapy of patients with AN. Due to the observed correlation with BMI, GI complaints after ingestion of fructose or lactose likely develop with decreasing body weight and are potentially reversible with weight regain.

Specific Changes in the Mammalian Gut Microbiome as a Biomarker for Oxytocin-Induced Behavioral Changes

Prolonged exposure to psychiatric pharmacological agents is often associated with marked gastrointestinal phenomena, including changes in food intake, bowel motility, gastric emptying, and transit time. Those changes are reflected in the gut microbiota composition of the patient and can, therefore, be objectively measured. This is in contrast to the standard psychiatric evaluation of patients, which includes symptoms that are subjectively assessed (i.e., mood, anxiety level, perception, thought disorders, etc.). The association between a drug’s effect on the microbiota and psychiatric symptoms may allow for quantifiable surrogate markers of treatment effectiveness. Changes in the levels of specific drug-sensitive bacterial species can, thus, potentially serve as biomarkers for the intake and effectiveness of psychiatric drugs. Here, we show substantial microbiota changes that were associated with oxytocin administration and the decreased anxiety/depression-like behaviors it conferred in a rat model of corticosterone-induced stress. Compared with oxytocin, citalopram produced more minor effects on the rats’ microbiota. Alterations in the gut microbiota may, therefore, reflect the consumption and effectiveness of some psychiatric drugs.

Fecal Microbial and Metabolomic Change during treatment course for depression: An Observational Study

BACKGROUND

There is growing evidence regarding the connection between alterations in gut microbiota and their metabolites in patients with depressive disorders, suggesting a potential role in pathophysiology. Our study aimed to investigate the relationship between microbial, metabolomic features and the course of treatment for depression in a real-world clinical setting.

METHODS

Patients diagnosed with depressive disorders were recruited, and their stool was collected at three time points during their depression treatments. Patients were divided into three groups: non-responders, responders, and stable remitters. Gut microbiomes were analyzed using 16S rRNA gene sequencing, and gut metabolomes were analyzed by a mass spectrometry approach. Microbiomes/metabolomes were compared between groups cross-sectionally and longitudinally.

RESULTS

A total of 33 patients were recruited and divided into non-responders (n = 16), responders (n = 11), and stable remitters (n = 6). Non-responders presented lower alpha diversity in the Phylogenic Diversity index compared to responders during the treatment course (p = 0.003). Non-responders presented increased estimated glutamate synthesis functions by the microbiota compared to responders and stable remitters (p = 0.035). There were no specific microbiota or metabolome that differentiated the three groups.

LIMITATIONS

Small sample size with no healthy controls.

CONCLUSIONS

Our results indicate that both cross-sectional microbial features and longitudinal microbial transitions are different depending on the treatment course of depression. Controlled studies, as well as animal studies, are needed in the future to elucidate the causal relationship between microbiota and depression.

The Microbiota-Gut-Brain Axis in Mental Health and Medication Response: Parsing Directionality and Causality

There is increasing evidence for the role of the microbiome in various mental health disorders. Moreover, there has been a growing understanding of the importance of the microbiome in mediating both the efficacy and side effects of various medications, including psychotropics. In this issue, Tomizawa and colleagues report on the effect of psychotropic drugs on the gut microbiome of 40 patients with depression and/or anxiety disorders. In their longitudinal cohort, the authors find that antipsychotics, but not anxiolytics, decrease microbiome alpha diversity. They further find that antipsychotics dosage was negatively correlated with alpha diversity in these patients. The health consequences of these microbiome alterations remain to be fully understood. In this commentary, we will discuss such findings through the lens of several recent studies on the microbiota-gut-brain axis. We also use the paper as a backdrop to discuss directionality and, by extension, causality in relation to microbiota-gut-brain-brain signaling.

Probiotic consumption relieved human stress and anxiety symptoms possibly via modulating the neuroactive potential of the gut microbiota

Stress has been shown to disturb the balance of human intestinal microbiota and subsequently causes mental health problems like anxiety and depression. Our previous study showed that ingesting the probiotic strain, Lactobacillus (L.) plantarum P-8, for 12 weeks could alleviate stress and anxiety of stressed adults. The current study was a follow-up work aiming to investigate the functional role of the gut metagenomes in the observed beneficial effects. The fecal metagenomes of the probiotic (n = 43) and placebo (n = 36) receivers were analyzed in depth. The gut microbiomes of the placebo group at weeks 0 and 12 showed a significantly greater Aitchison distance (P < 0.001) compared with the probiotic group. Meanwhile, the Shannon diversity index of the placebo group (P < 0.05) but not the probiotic group decreased significantly at week 12. Additionally, significantly more species-level genome bins (SGBs) of Bifidobacterium adolescentis, Bifidobacterium longum, and Fecalibacterium prausnitzii (P < 0.01) were identified in the fecal metagenomes of the probiotic group, while the abundances of SGBs representing the species Roseburia faecis and Fusicatenibacter saccharivorans decreased significantly (P < 0.05). Furthermore, the 12-week probiotic supplementation enhanced the diversity of neurotransmitter-synthesizing/consuming SGBs and the levels of some predicted microbial neuroactive metabolites (e.g., short-chain fatty acids, gamma-aminobutyric acid, arachidonic acid, and sphingomyelin). Our results showed a potential link between probiotic-induced gut microbiota modulation and stress/anxiety alleviation in stressed adults, supporting that the gut-brain axis was involved in relieving stress-related symptoms. The beneficial effect relied not only on microbial diversity changes but more importantly gut metagenome modulations at the SGB and functional gene levels.

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Stress and anxiety are related to gut dysbiosis.

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Ingesting Lactobacillus plantarum P-8 (P-8) improved stress/anxiety symptoms.

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Symptoms were relieved by modulating gut microbiota and neuroactive potential.