Early life adversity predicts brain-gut alterations associated with increased stress and mood

Early life adversity impacts alterations in brain structure and food addiction in individuals with high BMI

Obesity and food addiction are associated with distinct brain signatures related to reward processing, and early life adversity (ELA) also increases alterations in these same reward regions. However, the neural mechanisms underlying the effect of early life adversity on food addiction are unknown. Therefore, the aim of this study was to examine the interactions between ELA, food addiction, and brain morphometry in individuals with obesity. 114 participants with high body mass index (BMI) underwent structural MRIs, and completed several questionnaires (e.g., Yale Food Addiction Scale (YFAS), Brief Resilience Scale (BRS), Early Traumatic Inventory (ETI)). Freesurfer 6 was applied to generate the morphometry of brain regions. A multivariate pattern analysis was used to derive brain morphometry patterns associated with food addiction. General linear modeling and mediation analyses were conducted to examine the effects of ELA and resilience on food addiction in individuals with obesity. Statistical significance was determined at a level of p < 0.05. High levels of ELA showed a strong association between reward control brain signatures and food addiction (p = 0.03). Resilience positively mediated the effect of ELA on food addiction (B = 0.02, p = 0.038). Our findings suggest that food addiction is associated with brain signatures in motivation and reward processing regions indicative of dopaminergic dysregulation and inhibition of cognitive control regions. These mechanistic variabilities along with early life adversity suggest increased vulnerability to develop food addiction and obesity in adulthood, which can buffer by the neuroprotective effects of resilience, highlighting the value of incorporating cognitive appraisal into obesity therapeutic regimens.

Association between Chronic Misophonia-Induced Stress and Gastrointestinal Pathology in Children-A Hypothesis

Misophonia is a neurophysiological disorder with behavioral implications, is complex and multifactorial in origin, and is characterized by an atypical and disproportionate emotional response to specific sounds or associated visual stimuli. Triggers include human-generated sounds, mainly sounds related to feeding and breathing processes, and repetitive mechanical sounds. In response to the triggering stimulus, the patient experiences immediate, high-intensity, disproportionate physical and emotional reactions that affect their quality of life and social functioning. The symptoms of misophonia can occur at any age, but onset in childhood or adolescence is most common. Affected children live in a constant state of anxiety, suffer continuous physical and emotional discomfort, and are thus exposed to significant chronic stress. Chronic stress, especially during childhood, has consequences on the main biological systems through the dysregulation of the hypothalamic-pituitary-adrenal axis, including the gastrointestinal tract. Here, we provide arguments for a positive correlation between misophonic pathology and gastrointestinal symptoms, and this hypothesis may be the starting point for further longitudinal studies that could investigate the correlations between these childhood vulnerabilities caused by misophonia and their effect on the gastrointestinal system. Further research to study this hypothesis is essential to ensure correct and timely diagnosis and optimal psychological and pharmacological support.

Long-term neurocognitive, psychosocial, and physical outcomes after prenatal exposure to radiotherapy: a multicentre cohort study of the International Network on Cancer, Infertility, and Pregnancy

BACKGROUND

The main data available on the safety of radiation during pregnancy originate from animal studies and from studies of survivors of atomic or nuclear disasters. The effect of radiotherapy to treat maternal cancer on fetal development is uncertain. This report presents a unique cohort and aims to determine the long-term neurocognitive, psychosocial and physical outcomes of offspring of mothers treated with radiotherapy during pregnancy.

METHODS

In this international, multicentre, mixed retrospective-prospective cohort study, we recruited participants between Aug 5, 2006, and Aug 24, 2023, aged between 1·5 and 46 years, at three referral centres in Belgium, the Netherlands, and the USA. Participants were eligible if they were born from mothers treated with radiotherapy during pregnancy. Fetal radiation doses were obtained from medical records and participants were followed up at predefined ages (1·5, 3, 6, 9, 12, 15, and 18 years) and 5-yearly in adulthood, based on age at enrolment, using a neurocognitive test battery (measuring intelligence, attention, and memory), parent-reported executive function and psychosocial questionnaires, and a medical assessment. Results were compared with test-specific normative data. Linear regression models investigated associations between radiotherapy factors (fetal radiation dose, gestational age at the start and end of radiotherapy, and radiotherapy duration) and outcomes.

FINDINGS

68 maternal cases of radiotherapy during pregnancy were registered by the three participating centres, of which 61 resulted in a livebirth and were therefore eligible to participate in the child follow-up study. After excluding those who did not give consent, 43 participants born from 42 mothers treated with radiotherapy during pregnancy were included in the study (median age at first assessment 3 years [IQR 2-11]; median age at last assessment 12 years [9-18]; median number of assessments two [1-4]). 18 (42%) of the included participants were female and 25 (58%) male, and 37 (86%) were of White ethnicity. Mean neurocognitive outcomes of the entire cohort were within normal ranges. No associations were found with fetal radiation dose or timing of radiotherapy during pregnancy. Six (16%) of 38 participants with neurocognitive outcomes scored lower than one SD on at least one neurocognitive outcome, three (7%) reported chronic medical conditions (spasmophilia, spastic diplegia, and IgG deficiency), and three (7%) were diagnosed with attention-deficit hyperactivity disorder (of whom two scored lower on attention). Of ten (23%) participants with lower neurocognitive score(s), a chronic medical condition, or attention-deficit hyperactivity disorder, eight were born preterm. The remaining 33 (77%) participants showed no neurocognitive, psychosocial, or chronic physical problems.

INTERPRETATION

We show on average normal neurocognitive, psychosocial, and physical outcomes after prenatal exposure to radiotherapy. Differences in outcomes could not be explained by exposure to radiotherapy during pregnancy. These results suggest that extra-abdomino-pelvic radiotherapy exposure during pregnancy in general does not adversely affect outcomes of liveborn children. Further research with a larger sample is necessary to confirm these findings.

FUNDING

Kom Op Tegen Kanker, KWF Kankerbestrijding, Stichting Tegen Kanker, Research Foundation Flanders.

Transgenerational effects of early life stress on the fecal microbiota in mice

Stress in early life can affect the progeny and increase the risk to develop psychiatric and cardiometabolic diseases across generations. The cross-generational effects of early life stress have been modeled in mice and demonstrated to be associated with epigenetic factors in the germline. While stress is known to affect gut microbial features, whether its effects can persist across life and be passed to the progeny is not well defined. Here we show that early postnatal stress in mice shifts the fecal microbial composition (binary Jaccard index) throughout life, including abundance of eight amplicon sequencing variants (ASVs). Further effects on fecal microbial composition, structure (weighted Jaccard index), and abundance of 16 ASVs are detected in the progeny across two generations. These effects are not accompanied by changes in bacterial metabolites in any generation. These results suggest that changes in the fecal microbial community induced by early life traumatic stress can be perpetuated from exposed parent to the offspring.

Early-life stress and the gut microbiome: A comprehensive population-based investigation

Early-life stress (ELS) has been robustly associated with a range of poor mental and physical health outcomes. Recent studies implicate the gut microbiome in stress-related mental, cardio-metabolic and immune health problems, but research on humans is scarce and thus far often based on small, selected samples, often using retrospective reports of ELS. We examined associations between ELS and the human gut microbiome in a large, population-based study of children. ELS was measured prospectively from birth to 10 years of age in 2,004 children from the Generation R Study. We studied overall ELS, as well as unique effects of five different ELS domains, including life events, contextual risk, parental risk, interpersonal risk, and direct victimization. Stool microbiome was assessed using 16S rRNA sequencing at age 10 years and data were analyzed at multiple levels (i.e. α- and β-diversity indices, individual genera and predicted functional pathways). In addition, we explored potential mediators of ELS-microbiome associations, including diet at age 8 and body mass index at 10 years. While no associations were observed between overall ELS (composite score of five domains) and the microbiome after multiple testing correction, contextual risk - a specific ELS domain related to socio-economic stress, including risk factors such as financial difficulties and low maternal education - was significantly associated with microbiome variability. This ELS domain was associated with lower α-diversity, with β-diversity, and with predicted functional pathways involved, amongst others, in tryptophan biosynthesis. These associations were in part mediated by overall diet quality, a pro-inflammatory diet, fiber intake, and body mass index (BMI). These results suggest that stress related to socio-economic adversity - but not overall early life stress - is associated with a less diverse microbiome in the general population, and that this association may in part be explained by poorer diet and higher BMI. Future research is needed to test causality and to establish whether modifiable factors such as diet could be used to mitigate the negative effects of socio-economic adversity on the microbiome and related health consequences.

Adverse childhood experience and depression: the role of gut microbiota

Depression is the most common psychiatric disorder that burdens modern society heavily. Numerous studies have shown that adverse childhood experiences can increase susceptibility to depression, and depression with adverse childhood experiences has specific clinical-biological features. However, the specific neurobiological mechanisms are not yet precise. Recent studies suggest that the gut microbiota can influence brain function and behavior associated with depression through the "microbe-gut-brain axis" and that the composition and function of the gut microbiota are influenced by early stress. These studies offer a possibility that gut microbiota mediates the relationship between adverse childhood experiences and depression. However, few studies directly link adverse childhood experiences, gut microbiota, and depression. This article reviews recent studies on the relationship among adverse childhood experiences, gut microbiota, and depression, intending to provide insights for new research.

Exploring the interplay between posttraumatic stress disorder, gut microbiota, and inflammatory biomarkers: a comprehensive meta-analysis

Introduction

Posttraumatic stress disorder (PTSD) is the most common mental health disorder to develop following exposure to trauma. Studies have reported conflicting results regarding changes in immune biomarkers and alterations in the abundance of bacterial taxa and microbial diversity in patients with PTSD.

Aim

The purpose of this meta-analysis is to summarize existing studies examining gut microbiota characteristics and changes in immune biomarkers in patients with PTSD.

Methods

Relevant studies were systematically searched in PubMed, Scopus, and Embase, published in English between January 1, 1960, and December 1, 2023. The outcomes included changes in abundance and diversity in gut microbiota (gut microbiota part) and changes in immune biomarkers (immune part).

Results

The meta-analysis included a total of 15 studies, with 9 focusing on changes in inflammatory biomarkers and 6 focusing on changes in gut microbiota composition in patients with PTSD. No differences were observed between groups for all inflammatory biomarkers (P≥0.05). Two of the six studies found that people with PTSD had less alpha diversity. However, the overall Standardized Mean Difference (SMD) for the Shannon Diversity Index was not significant (SMD 0.27, 95% CI -0.62-0.609, p = 0.110). Regarding changes in abundance, in two of the studies, a significant decrease in Lachnospiraceae bacteria was observed.

Conclusion

This meta-analysis provides a comprehensive overview of gut microbiota characteristics in PTSD, suggesting potential associations with immune dysregulation. Future research should address study limitations, explore causal relationships, and consider additional factors influencing immune function in individuals with PTSD.

Systematic review registration

https://www.crd.york.ac.uk, identifier CRD42023476590.

Discrimination exposure impacts unhealthy processing of food cues: crosstalk between the brain and gut

Experiences of discrimination are associated with adverse health outcomes, including obesity. However, the mechanisms by which discrimination leads to obesity remain unclear. Utilizing multi-omics analyses of neuroimaging and fecal metabolites, we investigated the impact of discrimination exposure on brain reactivity to food images and associated dysregulations in the brain-gut-microbiome system. We show that discrimination is associated with increased food-cue reactivity in frontal-striatal regions involved in reward, motivation and executive control; altered glutamate-pathway metabolites involved in oxidative stress and inflammation as well as preference for unhealthy foods. Associations between discrimination-related brain and gut signatures were skewed towards unhealthy sweet foods after adjusting for age, diet, body mass index, race and socioeconomic status. Discrimination, as a stressor, may contribute to enhanced food-cue reactivity and brain-gut-microbiome disruptions that can promote unhealthy eating behaviors, leading to increased risk for obesity. Treatments that normalize these alterations may benefit individuals who experience discrimination-related stress.

Adverse childhood experiences and obesity linked to indicators of gut permeability and inflammation in adult women

Gut permeability may increase cardiovascular disease risk by allowing bacterial components (e.g., lipopolysaccharide or LPS) to enter the bloodstream, leading to low-grade inflammation. People with adverse childhood experiences (ACEs) consistently display evidence of chronic inflammation, but the source of this inflammation, and whether gut permeability may contribute, is unknown. Moreover, whether ACE status may further perturb obesity-associated gut permeability and inflammation is unknown. Women (N = 79, aged 18-84y) free of cardiometabolic diseases and inflammatory conditions and not regularly taking anti-inflammatory medications were included in a 2 × 2 factorial design with low or high ACE status (either 0 ACEs or 3+ ACEs) and body mass index (BMI) (either normal-weight [18.5-24.9 kg/m2; NW] or obesity [>30 kg/m2; OB]) as factors (n = 15-27/group). Serum LPS binding protein (LBP), soluble CD14 (sCD14), fatty-acid binding protein-2 (FABP2), LPS core IgM, and the ratio of LBP:sCD14 were used as indicators of gut permeability. Inflammatory markers C-reactive protein (CRP), tumor necrosis factor (TNF)-α, and interleukin (IL)-6 were also measured. Data were analyzed using 2-way ANCOVA (age-adjusted). LBP, LBP:sCD14 and FABP2 were higher in OB versus NW, regardless of ACE status (PBMI < 0.05). Higher ACE status was associated with increased circulating LBP:sCD14 and LPS core IgM (PACE < 0.05). sCD14 was unrelated to BMI or ACEs. CRP was elevated in OB versus NW (PBMI < 0.001) and tended to be higher with 3+ ACEs compared to 0 ACEs (PACE = 0.06). Moreover, TNF-α was greater in 3+ ACEs relative to 0 ACEs (PACE = 0.03). IL-6 was unrelated to BMI or ACE status. No interaction effects were observed for any marker of gut permeability or inflammation. In sum, ACE status and obesity were independently associated with evidence of gut permeability and systemic inflammation but did not interact in relation to indicators of gut permeability.

The impact of acute and chronic stress on gastrointestinal physiology and function: a microbiota-gut-brain axis perspective

The physiological consequences of stress often manifest in the gastrointestinal tract. Traumatic or chronic stress is associated with widespread maladaptive changes throughout the gut, although comparatively little is known about the effects of acute stress. Furthermore, these stress-induced changes in the gut may increase susceptibility to gastrointestinal disorders and infection, and impact critical features of the neural and behavioural consequences of the stress response by impairing gut-brain axis communication. Understanding the mechanisms behind changes in enteric nervous system circuitry, visceral sensitivity, gut barrier function, permeability, and the gut microbiota following stress is an important research objective with pathophysiological implications in both neurogastroenterology and psychiatry. Moreover, the gut microbiota has emerged as a key aspect of physiology sensitive to the effects of stress. In this review, we focus on different aspects of the gastrointestinal tract including gut barrier function as well as the immune, humoral and neuronal elements involved in gut-brain communication. Furthermore, we discuss the evidence for a role of stress in gastrointestinal disorders. Existing gaps in the current literature are highlighted, and possible avenues for future research with an integrated physiological perspective have been suggested. A more complete understanding of the spatial and temporal dynamics of the integrated host and microbial response to different kinds of stressors in the gastrointestinal tract will enable full exploitation of the diagnostic and therapeutic potential in the fast-evolving field of host-microbiome interactions.

Psychological Stress and Gut Microbiota Composition: A Systematic Review of Human Studies

INTRODUCTION

The associations between psychological stress and gut microbiota composition are not fully understood. This study investigated associations between psychological stress and gut microbiota composition and examined the potential modifying effects of age, sex, and ethnicity on such associations.

METHODS

A systematic literature search was conducted using PubMed, Web of Science, PsycINFO, and Embase databases for studies published until November 2021 which examined associations between psychological stress and gut microbiota composition.

RESULTS

During the search process, 10,790 studies were identified, and after screening, 13 met the eligibility criteria and were included. The median sample size was 70, and the median age of participants was 28.0 years. Most of the included studies did not report associations between measures of alpha- and beta diversity of the gut microbiota composition and psychological stress. A few studies reported that the Shannon index, Chao 1, Simpson index, and weighted UniFrac were negatively associated with psychological stress. Significant reductions in several taxa at the phyla-, family-, and genus-levels were observed in participants with higher psychological stress. At the phylum level, the abundance of Proteobacteria and Verrucomicrobia were negatively associated with psychological stress. At the family-level, no more than two studies reported associations of the same microbiota with psychological stress. At the genus level, the following results were found in more than two studies; psychological stress was negatively associated with the abundance of Lachnospira, Lachnospiraceae, Phascolarctobacterium, Sutterella, and Veillonella, and positively associated with the abundance of Methanobrevibacter, Rhodococcus, and Roseburia. However, it was not possible to determine the influence of age, sex, or ethnicity due to the limited studies included.

CONCLUSION

Our findings provide evidence that psychological stress is associated with changes in the abundance of the gut microbiota. Larger sample longitudinal studies are needed to determine the causal relationship between psychological stress and the gut microbiota.

Gut microbiota metabolites mediate the interplay between childhood maltreatment and psychopathology in patients with eating disorders

Eating disorders (EDs) are syndromes with a multifactorial etiopathogenesis, involving childhood traumatic experiences, as well as biological factors. Human microbiome has been hypothesised to play a fundamental role, impacting on emotion regulation, as well as with eating behaviours through its metabolites such as short chain fatty acids (SCFAs). The present study investigated the interactions between psychopathology of EDs, the gut microbiome and SCFAs resulting from bacterial community metabolic activities in a population of 47 patients with Anorexia Nervosa, Bulimia Nervosa, and Binge Eating Disorder and in healthy controls (HCs). Bacterial gut microbiota composition differences were found between subjects with EDs and HCs, especially in association with different pathological behaviours (binge-purge vs restricting). A mediation model of early trauma and ED-specific psychopathology linked reduction of microbial diversity to a typical microbiota-derived metabolite such as butyric acid. A possible interpretation for this model might be that childhood trauma represents a risk factor for gut dysbiosis and for a stable modification of mechanisms responsible for SCFAs production, and that this dysfunctional community is inherited in the passage from childhood to adulthood. These findings might open the way to novel interventions of butyric acid-like compounds as well as faecal transplant.

Brain-gut microbiome profile of neuroticism predicts food addiction in obesity: A transdiagnostic approach

Neuroticism is one of the most robust risk factors for addictive behaviors including food addiction (a key contributor to obesity), although the associated mechanisms are not well understood. A transdiagnostic approach was used to identify the neuroticism-related neuropsychological and gut metabolomic patterns associated with food addiction. Predictive modeling of neuroticism was implemented using multimodal features (23 clinical, 13,531 resting-state functional connectivity (rsFC), 336 gut metabolites) in 114 high body mass index (BMI ≥25 kg/m2) (cross-sectional) participants. Gradient boosting machine and logistic regression models were used to evaluate classification performance for food addiction. Neuroticism was significantly associated with food addiction (P < 0.001). Neuroticism-related features predicted food addiction with high performance (89% accuracy). Multimodal models performed better than single-modal models in predicting food addiction. Transdiagnostic alterations corresponded to rsFC involved in the emotion regulation, reward, and cognitive control and self-monitoring networks, and the metabolite 3-(4-hydroxyphenyl) propionate, as well as anxiety symptoms. Neuroticism moderated the relationship between BMI and food addiction. Neuroticism drives neuropsychological and gut microbial signatures implicated in dopamine synthesis and inflammation, anxiety, and food addiction. Such transdiagnostic models are essential in identifying mechanisms underlying food addiction in obesity, as it can help develop multiprong interventions to improve symptoms.

Improved psychosocial measures associated with physical activity may be explained by alterations in brain-gut microbiome signatures

Obesity contributes to physical comorbidities and mental health consequences. We explored whether physical activity could influence more than metabolic regulation and result in psychological benefits through the brain-gut microbiome (BGM) system in a population with high BMI. Fecal samples were obtained for 16 s rRNA profiling and fecal metabolomics, along with psychological and physical activity questionnaires. Whole brain resting-state functional MRI was acquired, and brain connectivity metrics were calculated. Higher physical activity was significantly associated with increased connectivity in inhibitory appetite control brain regions, while lower physical activity was associated with increased emotional regulation network connections. Higher physical activity was also associated with microbiome and metabolite signatures protective towards mental health and metabolic derangements. The greater resilience and coping, and lower levels of food addiction seen with higher physical activity, may be explained by BGM system differences. These novel findings provide an emphasis on the psychological and resilience benefits of physical activity, beyond metabolic regulation and these influences seem to be related to BGM interactions.

The Gut Microbiome in Early Life Stress: A Systematic Review

Exposure to early life stress (ELS), prenatal or postnatal during childhood and adolescence, can significantly impact mental and physical health. The role of the intestinal microbiome in human health, and particularly mental health, is becoming increasingly evident. This systematic review aims to summarize the clinical data evaluating the effect of ELS on the human intestinal microbiome. The systematic review (CRD42022351092) was performed following PRISMA guidelines, with ELS considered as exposure to psychological stressors prenatally and during early life (childhood and adolescence). Thirteen articles met all inclusion criteria, and all studies reviewed found a link between ELS and the gut microbiome in both prenatal and postnatal periods. However, we failed to find consensus microbiome signatures associated with pre- or postnatal stress, or both. The inconsistency of results is likely attributed to various factors such as different experimental designs, ages examined, questionnaires, timing of sample collection and analysis methods, small population sizes, and the type of stressors. Additional studies using similar stressors and validated stress measures, as well as higher-resolution microbiome analytical approaches, are needed to draw definitive conclusions about the links between stress and the human gut microbiome.

Resilience by design: How nature, nurture, environment, and microbiome mitigate stress and allostatic load

Resilience to psychological stress is defined as adaption to challenging life experiences and not the absence of adverse life events. Determinants of resilience include personality traits, genetic/epigenetic modifications of genes involved in the stress response, cognitive and behavioral flexibility, secure attachment with a caregiver, social and community support systems, nutrition and exercise, and alignment of circadian rhythm to the natural light/dark cycle. Therefore, resilience is a dynamic and flexible process that continually evolves by the intersection of different domains in human’s life; biological, social, and psychological. The objective of this minireview is to summarize the existing knowledge about the multitude factors and molecular alterations that result from resilience to stress response. Given the multiple contributing factors in building resilience, we set out a goal to identify which factors were most supportive of a causal role by the current literature. We focused on resilience-related molecular alterations resulting from mind-body homeostasis in connection with psychosocial and environmental factors. We conclude that there is no one causal factor that differentiates a resilient person from a vulnerable one. Instead, building resilience requires an intricate network of positive experiences and a healthy lifestyle that contribute to a balanced mind-body connection. Therefore, a holistic approach must be adopted in future research on stress response to address the multiple elements that promote resilience and prevent illnesses and psychopathology related to stress allostatic load.

Early life adversity as a risk factor for cognitive impairment and Alzheimer's disease

Neurological conditions, including cognitive impairment and Alzheimer's disease (AD), impose a huge burden on society, affecting millions of people globally. In addition to genetic factors, recent studies indicate that environmental and experiential factors may contribute to the pathogenesis of these diseases. Early life adversity (ELA) has a profound impact on brain function and health later in life. In rodent models, exposure to ELA results in specific cognitive deficits and aggravated AD pathology. Extensive concerns have been raised regarding the higher risk of developing cognitive impairments in people with a history of ELA. In this review, we scrutinize findings from human and animal studies focusing on the connection of ELA with cognitive impairment and AD. These discoveries suggest that ELA, especially at early postnatal stages, increases susceptibility to cognitive impairment and AD later in life. In terms of mechanisms, ELA could lead to dysregulation of the hypothalamus-pituitary-adrenal axis, altered gut microbiome, persistent inflammation, oligodendrocyte dysfunction, hypomyelination, and aberrant adult hippocampal neurogenesis. Crosstalks among these events may synergistically contribute to cognitive impairment later in life. Additionally, we discuss several interventions that may alleviate adverse consequences of ELA. Further investigation into this crucial area will help improve ELA management and reduce the burden of related neurological conditions.

Advances in stress and depression research

PURPOSE OF REVIEW

Stress plays a central role in the onset and course of depression. However, only a subset of people who encounter stressful life events go on to experience a depressive episode. The current review highlights recent advances in understanding when, why, and for whom the stress-depression link occurs, and we identify avenues for future research.

RECENT FINDINGS

In the last 18 months, researchers have taken a more nuanced perspective on the biopsychosocial mechanisms critical to the stress-depression link. For example, examination of specific facets of emotion regulation, including emotion regulation flexibility and interpersonal emotion regulation, has been critical to understanding its role in depression. Similarly, refined investigations of social support allowed researchers to identify distinct - and occasionally opposite - outcomes depending on the context or manner in which the support was provided. Researchers also documented that the stress-depression link was enhanced by dysregulation of several stress-sensitive biological systems, such as the immune system, microbiome, endocrine system, and neuroanatomical substrates.

SUMMARY

Recent studies highlight the importance of adopting a nuanced understanding of mechanisms and moderators that explain the stress-depression link. We also encourage continued engagement in collaborative, open science that uses multiple methods to study the full breadth of human diversity.

Dietary interventions, the gut microbiome, and aggressive behavior: Review of research evidence and potential next steps

Research in biosocial criminology and other related disciplines has established links between nutrition and aggressive behavior. In addition to observational studies, randomized trials of nutritional supplements like vitamins, omega-3 fatty acids, and folic acid provide evidence of the dietary impact on aggression. However, the exact mechanism of the diet-aggression link is not well understood. The current article proposes that the gut microbiome plays an important role in the process, with the microbiota-gut-brain axis serving as such a mediating mechanism between diet and behavior. Based on animal and human studies, this review synthesizes a wide array of research across several academic fields: from the effects of dietary interventions on aggression, to the results of microbiota transplantation on socioemotional and behavioral outcomes, to the connections between early adversity, stress, microbiome, and aggression. Possibilities for integrating the microbiotic perspective with the more traditional, sociologically oriented theories in criminology are discussed, using social disorganization and self-control theories as examples. To extend the existing lines of research further, the article considers harnessing the experimental potential of noninvasive and low-cost dietary interventions to help establish the causal impact of the gut microbiome on aggressive behavior, while adhering to the high ethical standards and modern research requirements. Implications of this research for criminal justice policy and practice are essential: not only can it help determine whether the improved gut microbiome functioning moderates aggressive and violent behavior but also provide ways to prevent and reduce such behavior, alone or in combination with other crime prevention programs.

Antibiotic-induced microbiota depletion in normally-reared adult rats mimics the neuroendocrine effects of early life stress

Early life stress induced by maternal separation (MS) causes neuroendocrine, behavioral, and metabolic alterations that are related to gut dysbiosis. MS also increases microglial activation and decreases neurogenesis. Whether these long-term alterations are maintained or worsened in the absence of gut microbiota remains unknown. Hence, this study evaluated the effect of MS symptomatology after antibiotic-induced microbiota depletion (AIMD) in adult rats. Control and maternally separated (3 h per day from postnatal day one to 14, MS180) rats were subjected to AIMD for one month, then assessed for behavioral, metabolic, and neuroendocrine responses. Effects of MS180 and AIMD on gut microbiota were confirmed by qPCR. The data indicate that MS180 caused a passive coping strategy in the forced swimming test and decreased hippocampal neurogenesis. In addition, fasting glucose, cholesterol, and corticosterone levels increased, which correlated with a decrease in Lactobacillus spp counts in the caecum. AIMD also increased immobility in the forced swimming test, decreased hippocampal neurogenesis, and augmented corticosterone levels. However, it had no effects on glucose homeostasis or plasma lipid levels. Furthermore, the MS180-induced long-term effects on behavior and neurogenesis were not affected by microbiota depletion. Meanwhile, the metabolic imbalance was partially reversed in MS180 + AIMD rats. These results show that AIMD mimics the behavioral consequences of MS180 but may prevent metabolic imbalance, suggesting that gut dysbiosis could be part of the mechanisms involved in the maintenance of the long-term consequences of early life stress.

The role of the immune system in posttraumatic stress disorder

Posttraumatic stress disorder (PTSD) develops in a subset of individuals upon exposure to traumatic stress. In addition to well-defined psychological and behavioral symptoms, some individuals with PTSD also exhibit elevated concentrations of inflammatory markers, including C-reactive protein, interleukin-6, and tumor necrosis factor-α. Moreover, PTSD is often co-morbid with immune-related conditions, such as cardiometabolic and autoimmune disorders. Numerous factors, including lifetime trauma burden, biological sex, genetic background, metabolic conditions, and gut microbiota, may contribute to inflammation in PTSD. Importantly, inflammation can influence neural circuits and neurotransmitter signaling in regions of the brain relevant to fear, anxiety, and emotion regulation. Given the link between PTSD and the immune system, current studies are underway to evaluate the efficacy of anti-inflammatory treatments in those with PTSD. Understanding the complex interactions between PTSD and the immune system is essential for future discovery of diagnostic and therapeutic tools.

Obesity is associated with a distinct brain-gut microbiome signature that connects Prevotella and Bacteroides to the brain's reward center

The prevalence of obesity has risen to its highest values over the last two decades. While many studies have either shown brain or microbiome connections to obesity, few have attempted to analyze the brain-gut-microbiome relationship in a large cohort adjusting for cofounders. Therefore, we aim to explore the connection of the brain-gut-microbiome axis to obesity controlling for such cofounders as sex, race, and diet. Whole brain resting state functional MRI was acquired, and connectivity and brain network properties were calculated. Fecal samples were obtained from 287 obese and non-obese participants (males n = 99, females n = 198) for 16s rRNA profiling and fecal metabolites, along with a validated dietary questionnaire. Obesity was associated with alterations in the brain's reward network (nucleus accumbens, brainstem). Microbial diversity (p = .03) and composition (p = .03) differed by obesity independent of sex, race, or diet. Obesity was associated with an increase in Prevotella/Bacteroides (P/B) ratio and a decrease in fecal tryptophan (p = .02). P/B ratio was positively correlated to nucleus accumbens centrality (p = .03) and negatively correlated to fecal tryptophan (p = .004). Being Hispanic, eating a standard American diet, having a high Prevotella/Bacteroides ratio, and a high nucleus accumbens centrality were all independent risk factors for obesity. There are obesity-related signatures in the BGM-axis independent of sex, race, and diet. Race, diet, P/B ratio and increased nucleus accumbens centrality were independent risk factors for obesity. P/B ratio was inversely related to fecal tryptophan, a metabolite related to serotonin biosynthesis, and positively related to nucleus accumbens centrality, a region central to the brain's reward center. These findings may expand the field of therapies for obesity through novel pathways directed at the BGM axis.

Associations Between Traumatic Stress, Brain Volumes and Post-traumatic Stress Disorder Symptoms in Children: Data from the ABCD Study

Reduced volumes in brain regions of interest (ROIs), primarily from adult samples, are associated with posttraumatic stress disorder (PTSD). We extended this work to children using data from the Adolescent Brain Cognitive Development (ABCD) Study® (N = 11,848; M_age = 9.92). Structural equation modeling and an elastic-net (EN) machine-learning approach were used to identify potential effects of traumatic events (TEs) on PTSD symptoms (PTSDsx) directly, and indirectly via the volumes 300 subcortical and cortical ROIs. We then estimated the genetic and environmental variation in the phenotypes. TEs were directly associated with PTSDsx (r = 0.92) in children, but their indirect effects (r < 0.0004)-via the volumes of EN-identified subcortical and cortical ROIs-were negligible at this age. Additive genetic factors explained a modest proportion of the variance in TEs (23.4%) and PTSDsx (21.3%), and accounted for most of the variance of EN-identified volumes of four of the five subcortical (52.4-61.8%) three of the nine cortical ROIs (46.4-53.3%) and cerebral white matter in the left hemisphere (57.4%). Environmental factors explained most of the variance in TEs (C = 61.6%, E = 15.1%), PTSDsx (residual-C = 18.4%, residual-E = 21.8%), right lateral ventricle (C = 15.2%, E = 43.1%) and six of the nine EN-identified cortical ROIs (C = 4.0-13.6%, E = 56.7-74.8%). There is negligible evidence that the volumes of brain ROIs are associated with the indirect effects of TEs on PTSDsx at this age. Overall, environmental factors accounted for more of the variation in TEs and PTSDsx. Whereas additive genetic factors accounted for most of the variability in the volumes of a minority of cortical and in most of subcortical ROIs.

Stress gets into the belly: Early life stress and the gut microbiome

Research has established that stress "gets under the skin," impacting neuroendocrine and neuroimmune pathways to influence risk for physical and mental health outcomes. These effects can be particularly significant for early life stress (ELS), or adverse childhood experiences (ACEs). In this review, we explore whether stress gets "into the belly," that is, whether psychosocial stress affects the gut microbiome. We review animal and human research utilizing a variety of stress paradigms (acute laboratory stressors, chronic stress, stressful life events, perceived stress, ELS, in utero stress) and their impacts on the gut microbiota, with a particular focus on ELS. We also review data on dietary interventions to moderate impact of stress on the gut microbiome. Our review suggests strong evidence that acute laboratory stress, chronic stress, and ELS affect the gut microbiota in rodents, and growing evidence that perceived stress and ELS may impact the gut microbiota in humans. Emerging data also suggests, particularly in rodents, that dietary interventions such as omega-3 fatty acids and pre- and pro-biotics may buffer against the effects of stress on the gut microbiome, but more research is needed. In sum, growing evidence suggests that stress impacts not only the neuroendocrine and neuroimmune axes, but also the microbiota-gut-brain-axis, providing a pathway by which stress may get "into the belly" to influence health risk.