Sex differences in stress-related disorders: Major depressive disorder, bipolar disorder, and posttraumatic stress disorder

Patterns of Mental Health Service Utilisation: A Population-Based Linkage of Over 17 Years of Health Administrative Records

A cross-sectoral partnership was formed in 2021 in support of the recommendations in an audit on access to state-funded mental health services. In this first paper, we aimed to describe the demographic and service utilisation of adults with a mental health diagnosis in the Western Australian state-funded health system from 2005 to 2021. Inpatient, emergency department, specialised (ambulatory) community mental health service, and death records were linked in individuals aged ≥ 18 years with a mental health diagnosis in Western Australia. Altogether, 392,238 individuals with at least one mental health service contact between 1st January 2005 and 31st December 2021 were included for analysis. Females, Aboriginal and/or Torres Strait Islander people, and those who lived outside major cities or in the most disadvantaged areas were more likely to access state-funded mental health services. While the number of individuals who accessed community mental health services increased over time (from 28,769 in 2005 to 50,690 in 2021), the percentage increase relative to 2005 was notably greater for emergency department attendances (127% for emergency department; 76% for community; and 63% for inpatient). Conditions that contributed to the increase for emergency department were mainly alcohol disorder, reaction to severe stress and adjustment disorders, and anxiety disorders. Sex differences were observed between conditions. The pattern of access increased for emergency department and the community plus emergency department combination. This study confirmed that the patterns of access of state-funded mental health services have changed markedly over time and the potential drivers underlying these changes warrant further investigation.

DSP-6745, a novel 5-hydroxytryptamine modulator with rapid antidepressant, anxiolytic, antipsychotic and procognitive effects

BACKGROUND

Current treatment of major depressive disorder is facing challenges, including a low remission rate, late onset of efficacy, and worsening severity due to comorbid symptoms such as psychosis and cognitive dysfunction. Serotonin (5-HT) neurotransmission is involved in a wide variety of psychiatric diseases and its potential as a drug target continues to attract attention.

OBJECTIVES

The present study elucidates the effects of a novel 5-HT modulator, DSP-6745, on depression and its comorbid symptoms.

RESULTS

In vitro radioligand binding and functional assays showed that DSP-6745 is a potent inhibitor of 5-HT transporter and 5-HT2A, 5-HT2C, and 5-HT7 receptors. In vivo, DSP-6745 (6.4 and 19.1 mg/kg as free base, p.o.) increased the release of not only 5-HT, norepinephrine, and dopamine, but also glutamate in the medial prefrontal cortex. The results of in vivo mouse phenotypic screening by SmartCube® suggested that DSP-6745 has a behavioral signature combined with antidepressant-, anxiolytic-, and antipsychotic-like signals. A single oral dose of DSP-6745 (6.4 and 19.1 mg/kg) showed rapid antidepressant-like efficacy in the rat forced swim test, even at 24 h post-dosing, and anxiolytic activity in the rat social interaction test. Moreover, DSP-6745 (12.7 mg/kg, p.o.) led to an improvement in the apomorphine-induced prepulse inhibition deficit in rats. In the marmoset object retrieval with detour task, which is used to assess cognitive functions such as attention and behavioral inhibition, DSP-6745 (7.8 mg/kg, p.o.) enhanced cognition.

CONCLUSIONS

These data suggest that DSP-6745 is a multimodal 5-HT receptor antagonist and a 5-HT transporter inhibitor and has the potential to be a rapid acting antidepressant with efficacies in mitigating the comorbid symptoms of depression.

Patterns of gender inequality perception and depressive symptoms among Chinese adults: The mediating role of marital life satisfaction

OBJECTIVES

As one of the most severe public health issues, depressive symptoms have attracted wide attention around the world. This study aims to investigate the mediating role of marital life satisfaction in the relationship between gender inequality perception and depressive symptoms.

METHODS

Data were obtained from the China Family Panel Studies (CFPS) conducted in 2020. This study incorporated a total of 13,409 married residents aged 20 and above.

RESULTS

The residents with middle (B = 0.19, 95 % CI = 0.01, 0.40) or high perception of gender inequality (B = 0.55, 95 % CI = 0.34, 0.75) were more likely to develop depressive symptoms. Marital life satisfaction plays a mediating effect in the relationship between patterns of gender inequality perception and depressive symptoms, and the mediating effect accounted for 4.89 % or 1.37 % of the total impact in the residents with middle or high patterns of gender inequality perception.

LIMITATIONS

Further studies need to understand the mechanisms of perceived patterns of gender inequality and depressive symptoms, because the cross-sectional design in this study cannot draw causal inferences.

CONCLUSION

Patterns of gender inequality perception are significantly associated with depressive symptoms. Marital life satisfaction plays a mediating role in the relationship between patterns of gender inequality perception and depressive symptoms. It is plausible that nurturing healthy marital relationships could mitigate depressive symptoms in individuals who perceive high degrees of gender disparity.

Epigenetic mechanisms linking early-life adversities and mental health

Early-life adversities, whether prenatal or postnatal exposure, have been linked to adverse mental health outcomes later in life increasing the risk of several psychiatric disorders. Research on its neurobiological consequences demonstrated an association between exposure to adversities and persistent alterations in the structure, function, and connectivity of the brain. Consistent evidence supports the idea that regulation of gene expression through epigenetic mechanisms are involved in embedding the impact of early-life experiences in the genome and mediate between social environments and later behavioral phenotypes. In addition, studies from rodent models and humans suggest that these experiences and the acquired risk factors can be transmitted through epigenetic mechanisms to offspring and the following generations potentially contributing to a cycle of disease or disease risk. However, one of the important aspects of epigenetic mechanisms, unlike genetic sequences that are fixed and unchangeable, is that although the epigenetic markings are long-lasting, they are nevertheless potentially reversible. In this review, we summarize our current understanding of the epigenetic mechanisms involved in the mental health consequences derived from early-life exposure to malnutrition, maltreatment and poverty, adversities with huge and pervasive impact on mental health. We also discuss the evidence about transgenerational epigenetic inheritance in mammals and experimental data suggesting that suitable social and pharmacological interventions could reverse adverse epigenetic modifications induced by early-life negative social experiences. In this regard, these studies must be accompanied by efforts to determine the causes that promote these adversities and that result in health inequity in the population.

Early Handling Exerts Anxiolytic Effects and Alters Brain Mitochondrial Dynamics in Adult High Anxiety Mice

Early handling (EH), the brief separation of pups from their mother during early life, has been shown to exert beneficial effects. However, the impact of EH in a high anxiety background as well as the role of brain mitochondria in shaping EH-driven responses remain elusive.Here, we used a high (HAB) vs. normal (NAB) anxiety-related behavior mouse model to study how EH affects pup and dam behavior in divergent anxiety backgrounds. We also investigated EH-induced effects at the protein and mRNA levels in adult male HAB mice in the hypothalamus, the prefrontal cortex, and the hippocampus by examining the same mitochondrial/energy pathways and mitochondrial dynamics mechanisms (fission, fusion, biogenesis, and mitophagy) in all three brain regions.EH exerts anxiolytic effects in adult HAB but not NAB male mice and does not affect HAB or NAB maternal behavior, although basal HAB vs. NAB maternal behaviors differ. In adult HAB male mice, EH does not impact oxidative phosphorylation (OXPHOS) and oxidative stress in any of the brain regions studied but leads to increased protein expression of glycolysis enzymes and a correlation of anxiety-related behavior with Krebs cycle enzymes in HAB mice in the hypothalamus. Intriguingly, EH alters mitochondrial dynamics by increasing hypothalamic DRP1, OPA1, and PGC1a protein levels. At the mRNA level, we observe altered, EH-driven mitochondrial dynamics mRNA signatures which predominantly affect the prefrontal cortex.Taken together, our results show that EH exerts anxiolytic effects in adulthood in high anxiety and modulates mitochondrial dynamics pathways in a brain region-specific manner.

An Effect of Chronic Negative Stress on Hippocampal Structures and Functional Connectivity in Patients with Depressive Disorder

Purpose

Depressive disorder is a mental health disorder with complicated etiopathogenesis. Environmental stress and neurodevelopment combined with other factors contribute to the occurrence of depression. Especially for the depressive disorder with chronic negative stress, it has characteristics of recurrence and poor curative effect because of unclear mechanism. Here, we investigated the hippocampal structures and functional connectivity (FC) according to resting-state functional magnetic resonance imaging in patients with depression who underwent chronic negative stress.

Patients and Methods

A total of 65 patients with depression (34 underwent chronic negative stress and 31 non-underwent chronic negative stress) and 30 healthy controls who did not undergo chronic negative stress were included in the study. The volumes of hippocampal subfields, seed-based FCs between hippocampus and the whole brain voxels, and ROI-wise-based FC between hippocampal subfields were compared among the three groups.

Results

In the patients with depression who underwent chronic negative stress, the volumes of right_GC-ML-DG-head, right_CA4-head and right_CA3-head increased, FCs between Temporal_Mid_R, Precuneus_R, Frontal_Sup_R, Temporal_Sup_R, Angular_L, Frontal_Inf_Tri_R, Supp_Motor_Area_R, Precentral_L and hippocampus increased, and FCs between parasubiculum and CA3, and presubiculum and CA1 decreased. When compared to the patients who did not undergo chronic negative stress, the patients who underwent chronic negative stress had larger volumes of right_GC-ML-DG-head and right_CA3-head, higher FCs between Frontal_Sup_R, Frontal_Inf_Tri_R and hippocampus, and lower FCs between presubiculum and CA1.

Conclusion

The depression underwent chronic negative stress may experience disrupted hippocampal structures and functional connectivity. It may be one of potential depressive disorder subtypes.

The trends of mental disorders mortality in China over a 33-year period

OBJECTIVES

We investigated the variations in the trends of mental disorders mortality by age, period, and cohort, over a 33-year period from 1987 to 2020, to reveal the relationship between age, period, cohort, and mental disorders mortality, as well as providing guidance for resource allocation to prevent mental disorders-related deaths in vulnerable target populations.

METHODS

The data of mental disorders mortality 1987-2020 were from five administrative organizations, which collected from the National Health Commission in China with national monitoring by sex and age, covering 31 provinces in China. The International Classification of Diseases (ICD), its 9th Revision (ICD-9) and its 10th Revision were used to code the mental diseases. From 1987-2002, ICD-9 was used, and ICD-10 was used from 2003 to 2020. The age standardized mortality rates (ASMRs) were calculated using the World Standard Population as the reference. We used joinpoint models to assess the trends of mental disorders mortality in China for the period 1987-2020. And the age-period-cohort models were employed to estimate the age-period-cohort effect on mental disorders mortality.

RESULTS

The age-standardized overall mental disorders mortality rate (ASMR) showed a downward trend from 1987 to 2020. Further, the ASMR of individuals in urban was higher than that in rural from 1987 to 2001, but, post-2002, this urban-rural disparity in ASMR showed a less clear pattern, with urban areas occasionally surpassing rural areas and vice versa. ASMR is less prevalent among females compared to males overall. The contribution of age effects to mental disorders mortality gradually increases with advancing age, the period effects of mental disorders mortality gradually decrease over time. The cohort effect's contribution to mental disorders mortality decreases in the newly born population, while in the older birth cohorts, the cohort effect's contribution to the mortality rate of mental disorders increases.

CONCLUSIONS

The ASMR exhibits a decreasing trend from 1987 to 2020, and these change trend showed urban-rural and sex differences. The primary factors contributing to this overall decline are period effects and cohort effects. Our results provide valuable information for shaping mental health policies, designing targeted interventions, and preparing for future changes in disease mortality rates. The focus on different demographic factors allows for a nuanced and tailored approach to mental health promotion and intervention strategies.

Chronic exposure to imipramine induces a switch from depression-like to mania-like behavior in female serotonin transporter knockout rats: Role of BDNF signaling in the infralimbic cortex

BACKGROUND

Bipolar disorder (BD) is a highly burdensome psychiatric disorder characterized by alternating states of mania and depression. A major challenge in the clinic is the switch from depression to mania, which is often observed in female BD patients during antidepressant treatment such as imipramine. However, the underlying neural basis is unclear.

METHODS

To investigate the potential neuronal pathways, serotonin transporter knockout (SERT KO) rats, an experimental model of female BD patients, were subjected to a battery of behavioral tests under chronic treatment of the antidepressant imipramine. In addition, the expression of brain-derived neurotrophic factor (BDNF) and its downstream signaling was examined in the prefrontal cortex.

RESULTS

Chronic exposure to imipramine reduced anxiety and sociability and problem-solving capacity, and increased thigmotaxis and day/night activity in all animals, but specifically in female SERT KO rats, compared to female wild-type (WT) rats. Further, we found an activation of BDNF-TrkB-Akt pathway signaling in the infralimbic, but not prelimbic, cortex after chronic imipramine treatment in SERT KO, but not WT, rats.

LIMITATIONS

Repeated testing behaviors could potentially affect the results. Additionally, the imipramine induced changes in behavior and in the BDNF system were measured in separate animals.

CONCLUSIONS

Our study indicates that female SERT KO rats, which mirror the female BD patients with the 5-HTTLPR s-allele, are at higher risk of a switch to mania-like behaviors under imipramine treatment. Activation of the BDNF-TrkB-Akt pathway in the infralimbic cortex might contribute to this phenotype, but causal evidence remains to be provided.

Behavioural traits related with resilience or vulnerability to the development of cocaine-induced conditioned place preference after exposure of female mice to vicarious social defeat

Exposure to stress induced by intermittent repeated social defeat (IRSD) increases vulnerability to the development of cocaine-induced conditioned place preference (CPP) among male mice; however, some defeated mice are resilient to these effects of stress. In the present study we evaluated the effects of vicarious IRSD (VIRSD) in female mice and explored behavioural traits that are potentially predictive of resilience. C57BL/6 female mice (n = 28) were exposed to VIRSD, which consisted of the animals witnessing a short experience of social defeat by a male mouse on postnatal day (PND) 47, 50, 53 and 56. The control group (n = 10) was not exposed to stress. Blood samples were collected on PND 47 and 56 for corticosterone and interleukin-6 determinations. On PND 57-58, female mice performed several behavioural tests (elevated plus maze, hole-board, object recognition, social interaction, TST and splash tests). Three weeks later, the effects of cocaine (1.5 mg/kg) on the CPP paradigm were assessed. VIRSD decreased corticosterone levels (on PND 56), increased interleukin-6 levels, enhanced novelty-seeking, improved recognition memory and induced anxiety- and depression-like symptoms. Control and VIRSD female mice did not acquire CPP, although some stressed individuals with certain behavioural traits - including a high novelty-seeking profile or the development of depression-like behaviour in the splash test shortly after VIRSD - acquired cocaine CPP. Our results confirm that some behavioural traits of female mice are associated with vulnerability or resilience to the long-term effects of social stress on cocaine reward, as previously observed in males.

Activation of CRF/CRFR1 Signaling in the Central Nucleus of the Amygdala Contributes to Chronic Stress-Induced Exacerbation of Neuropathic Pain by Enhancing GluN2B-NMDA Receptor-Mediated Synaptic Plasticity in Adult Male Rats

Exacerbation of pain by chronic stress and comorbidity of pain with stress-related disorders such as depression and post-traumatic stress disorder, represent significant clinical challenges. Previously we have documented that chronic forced swim (FS) stress exacerbates neuropathic pain in spared nerve injury (SNI) rats, associated with an up-regulation of GluN2B-containing N-methyl-D-aspartate receptors (GluN2B-NMDARs) in the central nucleus of the amygdala (CeA). However, the molecular mechanisms underlying chronic FS stress (CFSS)-mediated exacerbation of pain sensitivity in SNI rats still remain unclear. In this study, we demonstrated that exposure of CFSS to rats activated the corticotropin-releasing factor (CRF)/CRF receptor type 1 (CRFR1) signaling in the CeA, which was shown to be necessary for CFSS-induced depressive-like symptoms in stressed rats, and as well, for CFSS-induced exacerbation of pain hypersensitivity in SNI rats exposed to chronic FS stress. Furthermore, we discovered that activation of CRF/CRFR1 signaling in the CeA upregulated the phosphorylation of GluN2B-NMDARs at tyrosine 1472 (pGluN2BY1472) in the synaptosomal fraction of CeA, which is highly correlated to the enhancement of synaptic GluN2B-NMDARs expression that has been observed in the CeA in CFSS-treated SNI rats. In addition, we revealed that activation of CRF/CRFR1 signaling in the CeA facilitated the CFSS-induced reinforcement of long-term potentiation as well as the enhancement of NMDAR-mediated excitatory postsynaptic currents in the basolateral amygdala (BLA)-CeA pathway in SNI rats. These findings suggest that activation of CRF/CRFR1 signaling in the CeA contributes to chronic stress-induced exacerbation of neuropathic pain by enhancing GluN2B-NMDAR-mediated synaptic plasticity in rats subjected to nerve injury. PERSPECTIVE: Our present study provides a novel mechanism for elucidating stress-induced hyperalgesia and highlights that the CRF/CRFR1 signaling and the GluN2B-NMDAR-mediated synaptic plasticity in the CeA may be important as potential therapeutic targets for chronic stress-induced pain exacerbation in human neuropathic pain. DATA AVAILABILITY: The data that support the findings of this study are available from the corresponding author upon reasonable request.

Mapping the global, regional and national burden of bipolar disorder from 1990 to 2019: trend analysis on the Global Burden of Disease Study 2019

BACKGROUND

Data on trends in the epidemiological burden of bipolar disorder are scarce.

AIMS

To provide an overview of trends in bipolar disorder burden from 1990 to 2019.

METHOD

Revisiting the Global Burden of Disease Study 2019, we analysed the number of cases, calculated the age-standardised rate (per 100 000 population) and estimated annual percentage change (EAPC) of incidence, prevalence and years lived with disability (YLDs) for bipolar disorder from 1990 to 2019. The independent effects of age, period and cohort were estimated by the age-period-cohort modelling.

RESULTS

Globally, the bipolar disorder-related prevalent cases, incident cases and number of YLDs all increased from 1990 to 2019. Regionally, the World Health Organization Region of the Americas accounted for the highest estimated YLD number and rate, with the highest age-standardised prevalence rate in 1990 and 2019 and highest EAPC of prevalence. By sociodemographic index (SDI) quintiles, all five SDI regions saw an increase in estimated incident cases. Nationally, New Zealand reported the highest age-standardised rate of incidence, prevalence and YLDs in 1990 and 2019. The most prominent age effect on incidence rate was in those aged 15-19 years. Decreased effects of period on incidence, prevalence and YLD rates was observed overall and in females, not in males. The incidence, prevalence and YLD rates showed an unfavourable trend in the younger cohorts born after 1990, with males reporting a higher cohort risk than females.

CONCLUSIONS

From 1990 to 2019, the overall trend of bipolar disorder burden presents regional and national variations and differs by age, sex, period and cohort.

Sex differences in body temperature and neural power spectra in response to repeated restraint stress

Repeated stress is associated with an increased risk of developing psychiatric illnesses such as post-traumatic stress disorder (PTSD), which is more common in women, yet the neurobiology behind this sex difference is unknown. Habituation to repeated stress is impaired in PTSD, and recent preclinical studies have shown that female rats do not habituate as fully as male rats to repeated stress, which leads to impairments in cognition and sleep. Further research should examine sex differences after repeated stress in other relevant measures, such as body temperature and neural activity. In this study, we analyzed core body temperature and EEG power spectra in adult male and female rats during restraint, as well as during sleep transitions following stress. We found that core body temperature of male rats habituated to repeated restraint more fully than female rats. Additionally, we found that females had a higher average beta band power than males on both days of restraint, indicating higher levels of arousal. Lastly, we observed that females had lower delta band power than males during sleep transitions on Day 1 of restraint, however, females demonstrated higher delta band power than males by Day 5 of restraint. This suggests that it may take females longer to initiate sleep recovery compared with males. These findings indicate that there are differences in the physiological and neural processes of males and females after repeated stress. Understanding the way that the stress response is regulated in both sexes can provide insight into individualized treatment for stress-related disorders.

Predictors of diagnostic conversion from major depression to bipolar disorder: a Swedish national longitudinal study

BACKGROUND

It is clinically important to predict the conversion of major depression (MD) to bipolar disorder (BD). Therefore, we sought to identify related conversion rates and risk factors.

METHODS

This cohort study included the Swedish population born from 1941 onward. Data were collected from Swedish population-based registers. Potential risk factors, including family genetic risk scores (FGRS), which were calculated based on the phenotypes of relatives in the extended family and not molecular data, and demographic/clinical characteristics from these registers were retrieved. Those with first MD registrations from 2006 were followed up until 2018. The conversion rate to BD and related risk factors were analyzed using Cox proportional hazards models. Additional analyses were performed for late converters and with stratification by sex.

RESULTS

The cumulative incidence of conversion was 5.84% [95% confidence interval (95% CI) 5.72-5.96] for 13 years. In the multivariable analysis, the strongest risk factors for conversion were high FGRS of BD [hazard ratio (HR) = 2.73, 95% CI 2.43-3.08], inpatient treatment settings (HR = 2.64, 95% CI 2.44-2.84), and psychotic depression (HR = 2.58, 95% CI 2.14-3.11). For late converters, the first registration of MD during the teenage years was a stronger risk factor when compared with the baseline model. When the interactions between risk factors and sex were significant, stratification by sex revealed that they were more predictive in females.

CONCLUSIONS

Family history of BD, inpatient treatment, and psychotic symptoms were the strongest predictors of conversion from MD to BD.

Insomnia as a Risk Factor for Substance Use Disorders in Women

Gender differences exist for both insomnia and substance use disorders. Women show a higher prevalence of insomnia and increased susceptibility to the effects of drugs than men. Importantly, a growing body of evidence suggests that insufficient sleep predicts and puts individuals at a higher risk for substance use and associated psychosocial problems. However, the role of insomnia in substance use disorders among women remains poorly understood. The present article discusses gender differences in insomnia and in substance use disorders and reviews evidence suggesting that an increased prevalence of insomnia may be a risk factor for substance use disorders in women.

Sex effects on differentiating patients with major depressive disorder from bipolar disorder in depressive state: A fMRI study with follow-up

BACKGROUND

Bipolar disorder (BD) is difficult to discriminate from major depressive disorder (MDD) before the appearance of mania or hypomania. This study was designed to identify whether patients with MDD and those who converted to BD are distinguishable using dynamic amplitude low-frequency fluctuations (dALFF) and describe the sex effects on the identification of the two disorders.

METHODS

We compared the dALFF values of 35 BD patients who converted from MDD during the 2-year follow-up, 99 MDD patients, and 130 healthy controls (HCs) using two-way ANOVA. Pearson's correlation was used to compare dALFF in dysfunctional brain regions and clinical characteristics.

RESULTS

A main effect of diagnosis was discovered in the frontal and occipital gyrus. For the main effect of sex, both the left middle occipital gyrus and the medial part of the superior frontal gyrus had higher dALFF values in males compared to females. An interaction of sex and diagnosis effect was observed in the right precentral gyrus. Male MDD patients exhibited a higher dALFF value than male BD patients. Additionally, we discovered a higher dALFF value in females than in males in BD patients. WCST scores were positively associated with dALFF values in the frontal and occipital gyrus in MDD patients. Meanwhile, dALFF values in the occipital gyrus positively correlated with WCST in female MDD patients only.

LIMITATION

Most of the participants were on medication and the sample size was small.

CONCLUSIONS

Our study is the first to find the non-neglectable role of sex effects in differentiating BD and MDD at an early stage.

Increased pituitary adenylate cyclase-activating polypeptide in the central bed nucleus of the stria terminalis in mood disorders in men

The mood disorders major depressive disorder (MDD) and bipolar disorder (BD) are highly prevalent worldwide. Women are more vulnerable to these psychopathologies than men. The bed nucleus of the stria terminalis (BNST), the amygdala and the hypothalamus are the crucial interconnected structures involved in the stress response. In mood disorders, stress systems in the brain are put into a higher gear. The BNST is implicated in mood, anxiety, and depression. The stress-related neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) is highly abundant in the central BNST (cBNST). In this study, we investigated alterations in PACAP in the cBNST of patients with mood disorders. Immunohistochemical (IHC) staining of PACAP and in situ hybridization (ISH) of PACAP mRNA were performed on the cBNST of post-mortem human brain samples. Quantitative IHC revealed elevated PACAP levels in the cBNST in both mood disorders, MDD and BD, but only in men, not in women. The PACAP ISH was negative, indicating that PACAP is not produced in the cBNST. The results support the possibility that PACAP innervation of the cBNST plays a role in mood disorder pathophysiology in men.

Connecting dots in disorders of gut-brain interaction: the interplay of stress and sex hormones in shaping visceral pain

Visceral pain and stress are tightly intertwined bodily and emotional phenomena, which enable a flexible adaptation to environmental challenges by activating a response repertoire to restore homeostasis along the gut-brain axis. However, visceral pain and stress can persist widely independent of the initial cause, acquiring independent disease values and posing major health burdens as predominant features in disorders of gut-brain interaction (DGBI). Epidemiological data consistently documents an increased prevalence for women to suffer from chronic visceral pain, possibly shaped by sex hormones and modulated by stress and its biological and psychosocial correlates. Yet, mechanisms underlying the complex interactions between altered visceroception, stress and sex remain widely elusive, especially in clinical populations with DGBI. We herein selectively review mechanisms of interactions between stress and sex in the complex pathophysiology of DGBI. A particular emphasis is laid on visceral pain, in which stress constitutes a major risk factor as well as mediator, and sex-related differences are particularly pronounced. Building on the neurobiology of stress and mechanisms of gut-brain interactions, we highlight putative target mechanisms via which visceral pain and stress may converge with sex effects into a triad. Accommodating a global demographic shift, we propose a lifespan perspective in future research, which may enable a more fine-tuned evaluation of this complex interplay exerting distinct challenges during vulnerable developmental phases. This viewpoint may advance our understanding of pathophysiological processes and can ultimately inspire novel tailored prevention strategies and therapeutic approaches in the treatment of chronic visceral pain and DGBI across the lifespan.

Gender and sex in eating disorders: A narrative review of the current state of knowledge, research gaps, and recommendations

INTRODUCTION

Eating disorders (EDs) have long been considered conditions exclusively affecting women, and studies in the ED field regularly exclude men. Research efforts are needed to better understand the role of gender and sex in EDs. This review describes the role of gender and sex in the development of EDs from a biopsychosocial perspective.

METHODS

The primary hypothesis of this narrative review is that gender and sex interact to influence ED risk. The literature review was conducted using the PubMed database.

RESULTS

This review first presents the general characteristics and prevalence of EDs according to gender and sex. Next, neurodevelopmental processes, neurobiology, gender roles, body image, and the minority stress model are addressed. Lastly, research perspectives to better include gender and sex in the field of EDs are discussed (e.g., representation of gender and sex diversities, development of appropriate assessment tools, and increasing awareness).

CONCLUSION

Although substantial knowledge gaps remain, there is a growing recognition of the importance of integrating gender and sex in ED research that holds promise for further development in the field.

Vicarious Social Defeat Increases Conditioned Rewarding Effects of Cocaine and Ethanol Intake in Female Mice

Stress is a critical factor in the development of mood and drug use disorders. The social defeat model is not appropriate for female rodents due to their low level of aggression. Therefore, a robust female model of social stress needs to be developed and validated. The aim of the present study was to unravel the long-lasting effects of vicarious social defeat (VSD) on the conditioned rewarding effects of cocaine and ethanol intake in female mice. Although VSD seems to be a good model for inducing behavioral and physiologic endophenotypes induced by stress, there are no studies to date that characterize the effect of VSD on cocaine or alcohol use. The results confirm that VSD females showed an increase in corticosterone levels after a vicarious experience while also displaying an increase in anxiety- and anhedonic-like behaviors. Three weeks after the last VSD, vicariously defeated female mice showed an increased developed preference for a non-effective dose of cocaine in the conditioned place preference (CPP) paradigm and showed an increase in ethanol intake. Our results suggest that female mice vicariously experience a state of distress through the social observation of others suffering from adverse events, confirming the use of VSD as a valid model to study the response to social stress in females. The fact that VSD in females induced a comparable behavioral phenotype to that observed in physically defeated males could indicate a relationship with the higher rate of psychopathologies observed in women. Notwithstanding, more studies are needed to dissect the neurobiological and behavioral peculiarities of the female response to social stress.

Are cognitive aspects of defense a core feature of anxiety and depression?

Anxiety and depression are highly prevalent behavior disorders, particularly in women. Recent preclinical work using animal models has been suboptimal in predicting the efficacy of drugs targeted at these conditions, suggesting a potential discrepancy between such models and the human disorders. Notably female animals tend to be equal to, or less responsive than, males in these tasks. A number of analyses suggest that mammalian defense patterns are complex: In addition to relatively discrete and immediate fight, flight, and freezing responses, a risk assessment pattern may occur in response to threat stimuli or situations with ambiguous elements. This pattern combines defensiveness with a number of cognition-linked behaviors such as sensory attention and orientation, approach, contact, and investigation of the potential threat. Studies measuring elements of this pattern suggest that female rats, and perhaps female mice, show higher levels than equivalent males. Higher female involvement may also occur in tasks involving learning/generalization/extinction of defensiveness to conditioned stimuli. Such findings are consonant with recent analyses of "female survival strategies" based on differential adaptiveness of cognitive components of defensiveness in females, due to the necessity of female care of offspring until they are independent. These data suggest the value of additional behavioral and functional analyses of cognitive aspects of defensive behavior; contributing to both an understanding of their underlying mechanisms, and providing more sensitive measures of drug responsivity for use with animal models.

Sex differences in cognitive flexibility are driven by the estrous cycle and stress-dependent

Stress is associated with psychiatric disorders such as post-traumatic stress disorder, major depressive disorder, anxiety disorders, and panic disorders. Women are more likely to be diagnosed with these stress-related psychiatric disorders than men. A key phenotype in stress-related psychiatric disorders is impairment in cognitive flexibility, which is the ability to develop new strategies to respond to different patterns in the environment. Because gonadal hormones can contribute to sex differences in response to stress, it is important to consider where females are in their cycle when exposed to stress and cognitive flexibility testing. Moreover, identifying neural correlates involved in cognitive flexibility could not only build our understanding of the biological mechanisms behind this crucial skill but also leads to more targeted treatments for psychiatric disorders. Although previous studies have separately examined sex differences in cognitive flexibility, stress effects on cognitive flexibility, and the effect of gonadal hormones on cognitive flexibility, many of the findings were inconsistent, and the role of the estrous cycle in stress-induced impacts on cognitive flexibility is still unknown. This study explored potential sex differences in cognitive flexibility using an operant strategy shifting-paradigm after either control conditions or restraint stress in freely cycling female and male rats (with estrous cycle tracking in the female rats). In addition, we examined potential neural correlates for any sex differences observed. In short, we found that stress impaired certain aspects of cognitive flexibility and that there were sex differences in cognitive flexibility that were driven by the estrous cycle. Specifically, stress increased latency to first press and trials to criterion in particular tasks. The female rats demonstrated more omissions and perseverative errors than the male rats; the sex differences were mostly driven by proestrus female rats. Interestingly, the number of orexinergic neurons was higher in proestrus female rats than in the male rats under control conditions. Moreover, orexin neural count was positively correlated with number of perseverative errors made in cognitive flexibility testing. In sum, there are sex differences in cognitive flexibility that are driven by the estrous cycle and are stress-dependent, and orexin neurons may underlie some of the sex differences observed.

Sex differences in the blood-brain barrier: Implications for mental health

Prevalence of mental disorders, including major depressive disorder (MDD), bipolar disorder (BD) and schizophrenia (SZ) are increasing at alarming rates in our societies. Growing evidence points toward major sex differences in these conditions, and high rates of treatment resistance support the need to consider novel biological mechanisms outside of neuronal function to gain mechanistic insights that could lead to innovative therapies. Blood-brain barrier alterations have been reported in MDD, BD and SZ. Here, we provide an overview of sex-specific immune, endocrine, vascular and transcriptional-mediated changes that could affect neurovascular integrity and possibly contribute to the pathogenesis of mental disorders. We also identify pitfalls in current literature and highlight promising vascular biomarkers. Better understanding of how these adaptations can contribute to mental health status is essential not only in the context of MDD, BD and SZ but also cardiovascular diseases and stroke which are associated with higher prevalence of these conditions.

Structure and function differences in the prelimbic cortex to basolateral amygdala circuit mediate trait vulnerability in a novel model of acute social defeat stress in male mice

Stressful life events are ubiquitous and well-known to negatively impact mental health. However, in both humans and animal models, there is large individual variability in how individuals respond to stress, with some but not all experiencing long-term adverse consequences. While there is growing understanding of the neurobiological underpinnings of the stress response, much less is known about how neurocircuits shaped by lifetime experiences are activated during an initial stressor and contribute to this selective vulnerability versus resilience. We developed a model of acute social defeat stress (ASDS) that allows classification of male mice into "susceptible" (socially avoidant) versus "resilient" (expressing control-level social approach) one hour after exposure to six minutes of social stress. Using circuit tracing and high-resolution confocal imaging, we explored differences in activation and dendritic spine density and morphology in the prelimbic cortex to basolateral amygdala (PL→BLA) circuit in resilient versus susceptible mice. Susceptible mice had greater PL→BLA recruitment during ASDS and activated PL→BLA neurons from susceptible mice had more and larger mushroom spines compared to resilient mice. We hypothesized identified structure/function differences indicate an overactive PL→BLA response in susceptible mice and used an intersectional chemogenetic approach to inhibit the PL→BLA circuit during or prior to ASDS. We found in both cases that this blocked ASDS-induced social avoidance. Overall, we show PL→BLA structure/function differences mediate divergent behavioral responses to ASDS in male mice. These results support PL→BLA circuit overactivity during stress as a biomarker of trait vulnerability and potential target for prevention of stress-induced psychopathology.

Functions of habenula in reproduction and socio-reproductive behaviours

Habenula is an evolutionarily conserved structure in the brain of vertebrates. Recent reports have drawn attention to the habenula as a processing centre for emotional decision-making and its role in psychiatric disorders. Emotional decision-making process is also known to be closely associated with reproductive conditions. The habenula receives innervations from reproductive centres within the brain and signals from key reproductive neuroendocrine regulators such as gonadal sex steroids, gonadotropin-releasing hormone (GnRH), and kisspeptin. In this review, based on morphological, biochemical, physiological, and pharmacological evidence we discuss an emerging role of the habenula in reproduction. Further, we discuss the modulatory role of reproductive endocrine factors in the habenula and their association with socio-reproductive behaviours such as mating, anxiety and aggression.

Sex-specific effects of low-dose hydrocortisone on threat detection in HIV

One sex differences in the perception of emotion is that females, particularly those with high anxiety, often show heightened identification of fearful faces. To better understand the causal role of glucocorticoids in this sex difference, we examine these associations in people with HIV(PWH) where emotion perception is impaired and mental health disorders are frequent. In a double-blind, placebo-controlled, cross-over study, we used a single low-dose of hydrocortisone (10 mg; LDH) as a mechanistic probe of the effects of elevated glucocorticoids on negative emotion perception in 65 PWH (31 women). The primary outcome was accuracy in identifying emotional expressions on the Facial Emotion Perception Test (FEPT). Salivary cortisol, self-reported stress/anxiety, and childhood trauma were also assessed. LDH increased salivary cortisol levels versus placebo. The effect of LDH versus placebo on FEPT accuracy depended on the combined influence of facial expression and sex (P = 0.03). LDH influenced accuracy only for women (P = 0.03), specifically for fearful faces (Cohen's d = 0.44, P = 0.04). Women's enhanced threat detection varied with psychological burden (mood, anxiety, and post-traumatic stress symptoms), more pronounced among those with lower burden and trauma (P < 0.05). This result suggests a role of the HPA axis in sex differences for perception of fearful faces in women with HIV, potentially due to changes in glucocorticoid receptor availability/activity, or improved integration of signals from facial recognition and emotion processing regions. The blunting of this effect in men and in individuals with more severe trauma suggests that the mechanisms underlying threat detection differ by sex and trauma history and warrant further investigation.

Sex-related differences in stressful events precipitating transient global amnesia - A retrospective observational study

INTRODUCTION

Physically or emotionally charged events have consistently been reported as precipitating an episode of transient global amnesia (TGA). In conjunction with evidence of hippocampal involvement from neuroimaging, this has promoted the hypothesis that TGA is a stress-related disorder.

METHODS

In this retrospective observational study, medical records of 389 patients with TGA were analysed regarding documented precipitating events, which were classified according to previously suggested criteria. Moreover, comorbidities and results of magnetic resonance imaging were collected.

FINDINGS

In our cohort of TGA patients, 231 were female (59.4%). A precipitating factor was identified in 266 patients (68.4%). Of these, 136 patients (51.1%) reported physical triggers, the most common being physical exertion (64.0%). Another 122 patients (45.9%) presented with an emotional trigger, most frequently classified as an interpersonal conflict (42.7%). In 8 cases (2.1%), TGA was preceded by a medical procedure. Emotional triggers were more often experienced by women (37.2% vs 22.8%, p = 0.003), while physical stressors were more often present in men (30.7% vs 41.1%, p = 0.035). Women had a significantly higher number of hippocampal MRI lesions than men (mean 1.13 vs 0.92; p = 0.042).

CONCLUSION

Our data suggest a female predominance in TGA occurrence and a sex-related difference in susceptibility to certain triggering events in TGA patients. In light of recent research on sex-specific differences in vulnerability to stress, these findings support the hypothesis that this might be a significant contributing factor in the pathogenesis of TGA.