The emerging role of the gut microbiome in posttraumatic stress disorder

Post-traumatic stress disorder, attention deficit and hyperactivity disorder, and 24 gastrointestinal diseases: Evidence from Mendelian randomization analysis

Post-traumatic stress disorder (PTSD) and Attention deficit and hyperactivity disorder (ADHD) are common mental illnesses. Observational studies have indicated that these conditions often co-occur with gastrointestinal diseases. However, the causal relationship between PTSD and ADHD with gastrointestinal diseases remain unclear. We conducted Mendelian randomization (MR) analysis to investigate these associations. We selected genetic instrument data with genome-wide significance levels for PTSD and ADHD from the psychiatric genomics consortium open genome-wide association study platform. Summary statistics for the 24 gastrointestinal diseases were obtained from the FinnGen study. We used the "TwoSampleMR" package in R to perform a 2-sample MR analysis and conducted sensitivity analysis of the results. We found that genetic susceptibility to PTSD was associated with 1 gastrointestinal disease, specifically pancreatic cancer (P = .003; odds ratios [OR] = 1.295; 95% CI, 1.094-1.531). Genetic susceptibility to ADHD was associated with 4 gastrointestinal diseases: gastroesophageal reflux (P = .014; OR = 1.100; 95% CI, 1.020-1.186), gastric ulcer (P = .004; OR = 1.208; 95% CI, 1.061-1.376), duodenal ulcer (P = .020; OR = 1.206; 95% CI, 1.029-1.413), and chronic gastritis (P = .021; OR = 1.122; 95% CI, 1.018-1.237). This study provides MR evidence supporting causal relationship between PTSD and ADHD with specific gastrointestinal diseases.

Cell-type-specific and inflammatory DNA methylation patterns associated with PTSD

BACKGROUND

Epigenetic modifications, including DNA methylation (DNAm), can change in response to traumatic stress exposure, and may help to distinguish between individuals with and without PTSD. Here, we examine the DNAm patterns specific to immune cell types and inflammation in those with PTSD.

METHODS

This study includes 3,277 participants from 11 cohorts participating in the Psychiatric Genomics Consortium (PGC) PTSD Epigenetics Workgroup. DNAm was assayed from blood with the MethylationEPIC BeadChip. A standardized QC pipeline was applied and used to impute cell composition. Within each cohort, we identified cell-type-specific DNAm patterns associated with PTSD, controlling for sex (if applicable), age, and ancestry. Meta-analyses were performed from summary statistics.

RESULTS

PTSD cases had lower proportions of B cells and NK cells as well as higher proportions of neutrophils when compared to trauma-exposed controls. Overall, we identified 96 PTSD-associated CpGs across six types of immune cells. Most of these differences were identified in B cells, with 95 % exhibiting lower methylation levels in those with PTSD. Interestingly, the PTSD-associated CpGs annotated to a gene in B cells were enriched in a recent GWAS of PTSD (p < 0.0001).

CONCLUSIONS

This study identifies novel PTSD-associated CpGs in individual immune cell types and supports the role of immune dysregulation and inflammation in PTSD.

Gut microbes: Therapeutic Target for neuropsychiatric disorders

Neuropsychiatric diseases encompass a range of mental and neurological disorders that have a significant and far-reaching effect on an individual's quality of life. These conditions affect not only the mental status but also the physical well-being of individuals, which leads to weakened immune systems and other diseases. Emerging research underscores a significant connection between the gut microbiome and neuropsychiatric diseases, suggesting that microbial communities within the gastrointestinal tract may influence brain function and mental health. Gut dysbiosis is caused by various factors, including stress, diet, inappropriate usage of antibiotics, infections, and so on, all of which can disrupt numerous pathways, resulting in abnormal neurotransmitter signaling, inflammation, and impaired brain function. Similarly, various neuropsychiatric diseases can disrupt the specific microbiome in the gut, leading to gut dysbiosis, often impairing memory and cognitive function. The growing evidence supporting the role of gut dysbiosis in neuropsychiatric disorders has opened up new avenues for therapeutic interventions. Modulating the gut microbiome through strategies such as probiotics, prebiotics, or fecal microbiota transplantation has shown promising results in various studies of neuropsychiatric disorders. However, further research is needed to fully elucidate the mechanisms involved in gut dysbiosis-associated brain changes to develop effective and personalized treatment strategies for neuropsychiatric diseases.

The Bidirectional Relationship Between the Gut Microbiome and Mental Health: A Comprehensive Review

The gut microbiome plays a fundamental role in mental health, influencing mood, cognition, and emotional regulation through the gut-brain axis. This bidirectional communication system connects the gastrointestinal and CNS, facilitated by microbial metabolites, neurotransmitters, and immune interactions. Recent research highlights the association between gut dysbiosis and psychiatric disorders, including anxiety, depression, and stress-related conditions. Key findings indicate that altered microbial diversity, decreased short-chain fatty acid (SCFA) production, and increased neuroinflammation contribute to mental health disturbances. This paper explores the mechanism linking the gut microbiome to brain function, including microbial neurotransmitter synthesis, vagus nerve signaling, and hypothalamic-pituitary-adrenal (HPA) axis modulation. Additionally, it evaluates the potential of microbiome-targeted interventions, such as probiotics, prebiotics, dietary modifications, and fecal microbiota transplantation (FMT), in alleviating psychiatric symptoms. Microbiome sequencing and bioinformatics advances further support the development of personalized microbiome-based mental health interventions. Despite promising evidence, challenges such as inter-individual variability, methodological inconsistencies, and the need for longitudinal studies remain. Future research should focus on standardizing microbiome assessment techniques and optimizing therapeutic applications. Integrating precision psychiatry with microbiome-based diagnostics holds immense potential in transforming mental health treatment.

Post-traumatic stress disorder: evolving conceptualization and evidence, and future research directions

The understanding of responses to traumatic events has been greatly influenced by the introduction of the diagnosis of post-traumatic stress disorder (PTSD). In this paper we review the initial versions of the diagnostic criteria for this condition and the associated epidemiological findings, including sociocultural differences. We consider evidence for post-traumatic reactions occurring in multiple contexts not previously defined as traumatic, and the implications that these observations have for the diagnosis. More recent developments such as the DSM-5 dissociative subtype and the ICD-11 diagnosis of complex PTSD are reviewed, adding to evidence that there are several distinct PTSD phenotypes. We describe the psychological foundations of PTSD, involving disturbances to memory as well as to identity. A broader focus on identity may be able to accommodate group and communal influences on the experience of trauma and PTSD, as well as the impact of resource loss. We then summarize current evidence concerning the biological foundations of PTSD, with a particular focus on genetic and neuroimaging studies. Whereas progress in prevention has been disappointing, there is now an extensive evidence supporting the efficacy of a variety of psychological treatments for established PTSD, including trauma-focused interventions - such as trauma-focused cognitive behavior therapy (TF-CBT) and eye movement desensitization and reprocessing (EMDR) - and non-trauma-focused therapies, which also include some emerging identity-based approaches such as present-centered and compassion-focused therapies. Additionally, there are promising interventions that are neither psychological nor pharmacological, or that combine a pharmacological and a psychological approach, such as 3,4-methylenedioxymethamphetamine (MDMA)-assisted psychotherapy. We review advances in the priority areas of adapting interventions in resource-limited settings and across cultural contexts, and of community-based approaches. We conclude by identifying future directions for work on trauma and mental health.

Grasping Posttraumatic Stress Disorder From the Perspective of Psychoneuroimmunoendocrinology: Etiopathogenic Mechanisms and Relevance for Integrative Management

Posttraumatic stress disorder (PTSD) is a debilitating condition caused by exposure to traumatic events that affects 5% to 10% of the population, with increased prevalence among women and individuals in war zones. Beyond psychological symptoms, PTSD induces significant physiological changes across systems. Psychoneuroimmunoendocrinology (PNIE) offers a framework to explore these complex interactions between the psyche and the nervous, immune, and endocrine systems. Studies have revealed that PTSD entails disruptions in the central and autonomic nervous, immune, and endocrine systems, including gut microbiota imbalances, which impair organ function. Integrative pathways that connect these parts include the microbiota-gut-brain axis, heart-brain axis, neuroinflammation, and hypothalamic-pituitary dysregulation, highlighting bidirectional links between mental and physical health. Viewing PTSD as an entity comprising both psychological and physiological challenges underscores the importance of integrative care strategies that combine pharmacological treatments, psychotherapy, and lifestyle interventions. These approaches are consistent with PNIE principles, which may help identify biomarkers for treatment efficacy. In this review, we discuss the pathophysiology of PTSD through a PNIE lens and its implications for improving patient care, advocating for personalized, multidisciplinary interventions in mental health.

Eating- and Weight-Related Disorders in the Armed Forces

BACKGROUND/OBJECTIVES

Like in the general population, the prevalences of eating- and weight-related health issues in the armed forces are increasing. Relevant medical conditions include the eating disorders (EDs) anorexia nervosa, bulimia nervosa, binge eating disorder, and avoidant restrictive food intake disorder (ARFID), as well as body dysmorphic disorder, muscle dysmorphia, and the relative energy deficiency in sport (RED-S) syndrome.

METHODS

We performed a narrative literature review on eating- and weight-related disorders in the armed forces.

RESULTS

Entry standards might exclude people with obesity, with EDs, or at high risk for EDs from entering the armed forces for military reasons and to protect the individual's health. Relevant potential risk factors of eating- and weight-related disorders in the military are the emphasis on appearance and fitness in the military, high levels of stress, military sexual trauma, post-traumatic stress disorder, deployment, relocation, long commutes, consumption of ultra-processed foods and beverages, limitations on food selection and physical exercise, and intensive combat training and field exercises. Eating- and weight-related disorders negatively impact professional military appearance and lead to problems with cardiorespiratory and neuromuscular fitness; daytime sleepiness; and a higher risk of musculoskeletal injuries, and other physical and mental health problems. Current and potential future therapeutic options include occupational health measures, psychosocial therapies, neuromodulation, and drug treatments.

CONCLUSIONS

Even though randomized controlled trials (RCTs) have been performed to test treatments for obesity in the armed forces, RCTs for the treatment of EDs, body dysmorphic disorder, muscle dysmorphia, and RED-S syndrome are lacking in the military context.

Impact of the gut microbiota-Th17 cell axis on inflammatory depression

Depression is a serious cognitive disorder that results in significant and pervasive deficits in social behavior. These deficits can be traced back to the intricate interplay between social, psychological, and biological factors. Inflammatory depression, a treatment-resistant or non-responsive subtype of depression, may be related to the interaction between the gut microbiota and interleukin-17-producing CD4+ T cells (Th17 cells). The heterogeneity, plasticity, and effector role of Th17 cells in depression may be influenced by microbiota factors. Commensals-elicited homeostatic Th17 cells preserve the morphological and functional integrity of the intestinal barrier. In addition to pathogen-elicited inflammatory Th17 cells, commensal-elicited homeostatic Th17 cells can become conditionally pathogenic and contribute to the development of inflammatory depression. This review delves into the possible involvement of Th17 cells in inflammatory depression and examines the interplay between gut microbiota and either homeostatic or inflammatory Th17 cells.

Post traumatic stress disorder associated hypothalamic-pituitary-adrenal axis dysregulation and physical illness

Conventional human stress responses are mediated by the sympathetic adrenal medullar (SAM) axis and the hypothalamic pituitary adrenal (HPA) axis. The SAM axis mediates the immediate response to stress through norepinephrine and epinephrine while the HPA axis mediates the slow response through corticosteroids, primarily cortisol, to effect systemic changes. Post Traumatic Stress Disorder (PTSD), a psychiatric disorder that develops in a small subset of people exposed to a traumatic event, may dysregulate these systems and result in increased risk of various clinical conditions. These conditions include but are not limited to cardiovascular disease, metabolic conditions, autoimmune diseases, neurocognitive disorders, and women's health complications such as preterm birth, polycystic ovarian syndrome, and endometriosis to name a few. This review focuses on how PTSD dysregulates the HPA axis, and further, how these alterations affect the immune system and physical health outcomes.

Dipeptide metabolite, glutamyl-glutamate mediates microbe-host interaction to boost spermatogenesis

The decrease in sperm count and infertility is a global issue that remains unresolved. By screening environmental bacterial isolates, we have found that a novel lactic acid bacterium, Lactiplantibacillus plantarum SNI3, increased testis size, testosterone levels, sperm count, sexual activity and fertility in mice that have consumed the bacteria for four weeks. The abundance of L. plantarum in the colon microbiome was positively associated with sperm count. Fecal microbiota transplantation (FMT) from L. plantarum SNI3-dosed mice improved testicular functions in microbiome-attenuated recipient animals. To identify mediators that confer pro-reproductive effects on the host, untargeted in situ mass spectrometry metabolomics was performed on testis samples of L. plantarum SNI3-treated and control mice. Enrichment pathway analysis revealed several perturbed metabolic pathways in the testis of treated mice. Within the testis, a dipeptide, glutamyl-glutamate (GluGlu) was the most upregulated metabolite following L. plantarum SNI3 administration. To validate the pro-reproductive feature of GluGlu, systemic and local injections of the dipeptide have been performed. γ-GluGlu increased sperm count but had no effect on testosterone. These findings highlight the role of γ-GluGlu in mediating spermatogenetic effects of L. plantarum on the male mouse host and -following relevant human clinical trials- may provide future tools for treating certain forms of male infertility.

New recognition of the heart-brain axis and its implication in the pathogenesis and treatment of PTSD

Post-traumatic stress disorder (PTSD) is a complex psychological disorder provoked by distressing experiences, and it remains without highly effective intervention strategies. The exploration of PTSD's underlying mechanisms is crucial for advancing diagnostic and therapeutic approaches. Current studies primarily explore PTSD through the lens of the central nervous system, investigating concrete molecular alterations in the cerebral area and neural circuit irregularities. However, the body's response to external stressors, particularly the changes in cardiovascular function, is often pronounced, evidenced by notable cardiac dysfunction. Consequently, examining PTSD with a focus on cardiac function is vital for the early prevention and targeted management of the disorder. This review undertakes a comprehensive literature analysis to detail the alterations in brain and heart structures and functions associated with PTSD. It also synthesizes potential mechanisms of heart-brain axis interactions relevant to the development of PTSD. Ultimately, by considering cardiac function, this review proposes novel perspectives for PTSD's prophylaxis and therapy.

DNA metabarcoding technology for the identification of the fecal microbiome in patients with chronic stress

In the latest research, the concept of stress is associated with the deregulation of several biological systems sensitive to stress, such as the immune system, the microbiome, the endocrine system and neuroanatomical substrates. The objective of the research was to identify the fecal microbiome in patients diagnosed with chronic stress and in healthy patients through a metabarcoding analysis. The methodology used fecal samples collected from 20 patients with stress and 20 healthy patients. For the diagnosis of stress, psychological tools previously validated by external researchers were used. For metabarcoding analysis, metagenomic DNA extraction was performed from the fecal samples. Next Generation Illumina genetic sequencing targeting the 16S rDNA gene was then performed, followed by bioinformatic analysis using QUIME II software. The results, at the psychological test level, 20 people with chronic stress were diagnosed, on the other hand, at the metabarcoding level, specifically at the Gender level, the Asteroleplasma bacteria present only in the 20 healthy patients was molecularly identified. On the other hand, the bacteria Alistipes and Bifidobacterium were identified with greater predominance in the 20 patients with stress. Concluding, the bacteria Alistipes and Bifidobacterium are candidates as possible markers of the intestinal microbiome in patients with chronic stress, and the bacteria Asteroleplasma are candidates as a bacterial marker of the intestinal microbiome in healthy people. Finally, the identification of the microbiome in patients with stress opens a new path to understanding stress and its relationship to dysregulation with the microbiome.

Molecular mechanisms and therapeutic possibilities of short-chain fatty acids in posttraumatic stress disorder patients: a mini-review

This mini-review explores the role of short-chain fatty acids (SCFAs) in posttraumatic stress disorder (PTSD). Highlighting the microbiota-gut-brain axis, this study investigated the bidirectional communication between the gut microbiome and mental health. SCFAs, byproducts of gut microbial fermentation, have been examined for their potential impact on PTSD, with a focus on molecular mechanisms and therapeutic interventions. This review discusses changes in SCFA levels and bacterial profiles in individuals with PTSD, emphasizing the need for further research. Promising outcomes from clinical trials using probiotics and fermented formulations suggest potential avenues for PTSD management. Future directions involve establishing comprehensive human cohorts, integrating multiomics data, and employing advanced computational methods, with the goal of deepening our understanding of the role of SCFAs in PTSD and exploring microbiota-targeted interventions.

The gut microbiota and post-traumatic major depression disorder: insights from bidirectional two-sample Mendelian randomization

Background

Exposure to trauma is often associated with an increased incidence of Major Depressive Disorder (MDD), yet the mechanisms underlying MDD development post-trauma remain elusive. The microbiota-gut-brain axis has been implicated in neuropsychiatric disorders, suggesting its potential role in post-traumatic MDD (PTMDD) development. Our study aimed to assess the significance of the gut microbiome-brain interaction in PTMDD.

Methods

We conducted a bidirectional two-sample Mendelian Randomization (MR) analysis to investigate the causal relationship between the gut microbiota and both PTMDD and trauma exposure in MDD. Genome-wide association study (GWAS) summary datasets for PTMDD and trauma exposure in MDD, both derived from the UK Biobank. The PTMDD dataset included 24,090 individuals (13,393 cases and 10,701 controls), while the dataset for trauma exposure in MDD comprised 22,880 participants (13,393 cases and 9,487 controls). Additionally, gut microbiota data from the MiBioGen consortium included 14,306 European individuals across 18 diverse cohorts.

Results

Our research identified a significant negative association between the phylum Verrucomicrobia (odds ratio (OR) [95% confidence interval (CI)] =0.799 [0.684-0.933], P=0.005) and the risk of developing PTMDD, suggesting a protective role for Verrucomicrobia against PTMDD. Conversely, our findings indicate no causal effects of the gut microbiota on trauma exposure in MDD. However, reverse analysis revealed that both PTMDD and MDD influence certain bacterial traits, affecting 5 and 9 bacterial traits, respectively. Moreover, Verrucomicrobia (OR [95% CI] = 1.166 [1.051 - 1.294], P=0.004) was found to be positively impacted by trauma exposure in MDD.

Conclusion

Our findings provide a cause-and-effect relationship between the gut microbiota and PTMDD, contributing to our understanding of the microbiota-gut-brain axis and its role in neuropsychiatric disorder development after trauma. This information provides an opportunity for new treatment and prevention methods which are aimed at the gut-brain interaction.

Single-Nucleus Transcriptome Profiling from the Hippocampus of a PTSD Mouse Model and CBD-Treated Cohorts

Post-traumatic stress disorder (PTSD) is the most common psychiatric disorder after a catastrophic event; however, the efficacious treatment options remain insufficient. Increasing evidence suggests that cannabidiol (CBD) exhibits optimal therapeutic effects for treating PTSD. To elucidate the cell-type-specific transcriptomic pathology of PTSD and the mechanisms of CBD against this disease, we conducted single-nucleus RNA sequencing (snRNA-seq) in the hippocampus of PTSD-modeled mice and CBD-treated cohorts. We constructed a mouse model by adding electric foot shocks following exposure to single prolonged stress (SPS+S) and tested the freezing time, anxiety-like behavior, and cognitive behavior. CBD was administrated before every behavioral test. The PTSD-modeled mice displayed behaviors resembling those of PTSD in all behavioral tests, and CBD treatment alleviated all of these PTSD-like behaviors (n = 8/group). Three mice with representative behavioral phenotypes were selected from each group for snRNA-seq 15 days after the SPS+S. We primarily focused on the excitatory neurons (ExNs) and inhibitory neurons (InNs), which accounted for 68.4% of the total cell annotations. A total of 88 differentially upregulated genes and 305 differentially downregulated genes were found in the PTSD mice, which were found to exhibit significant alterations in pathways and biological processes associated with fear response, synaptic communication, protein synthesis, oxidative phosphorylation, and oxidative stress response. A total of 63 overlapping genes in InNs were identified as key genes for CBD in the treatment of PTSD. Subsequent Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed that the anti-PTSD effect of CBD was related to the regulation of protein synthesis, oxidative phosphorylation, oxidative stress response, and fear response. Furthermore, gene set enrichment analysis (GSEA) revealed that CBD also enhanced retrograde endocannabinoid signaling in ExNs, which was found to be suppressed in the PTSD group. Our research may provide a potential explanation for the pathogenesis of PTSD and facilitate the discovery of novel therapeutic targets for drug development. Moreover, it may shed light on the therapeutic mechanisms of CBD.