The HPA axis in bipolar disorder: Systematic review and meta-analysis

Unraveling the role of the renin-angiotensin system in severe mental illnesses: An insight into psychopathology and cognitive deficits

Severe mental illnesses (SMI), especially schizophrenia and bipolar disorder (BD), are associated with significant distress to patients, reduced life expectancy and a higher cost of care. There is growing evidence that SMI may increase the risk of dementia in later life, posing an additional challenge in the management of these patients. SMI present a complex and highly heterogeneous pathophysiology, which has hampered the understanding of its underlying pathological mechanisms and limited the success of the available therapies. Despite the advances in therapeutic approaches in psychiatry over the past decades, treatment resistance is still a common problem in clinical practice, highlighting the urgent need for novel therapeutic targets for SMI. The discovery that renin-angiotensin system (RAS) components are expressed in the central nervous system opened new possibilities for investigating a potential role for this system in the neurobiology of SMI. The safety and efficacy of AT1 receptor blockers and angiotensin-converting enzyme inhibitors in cardiovascular and metabolic diseases, common medical comorbidities among SMI patients and well-known risk factors for dementia, suggest the potential scalability of these strategies for the management of SMI outcomes including the risk of subsequent dementia. This review aimed to discuss the available evidence from animal models and human studies of the potential involvement of RAS in the pathophysiology of SMI. We also provided a reflection on drawbacks and perspectives that can foster the development of new related therapeutic strategies.

Highfield imaging of the subgenual anterior cingulate cortex in uni- and bipolar depression

Background

The subgenual Anterior Cingulate Cortex (sgACC), as a part of the Anterior Cingulate Cortex and the limbic system plays a crucial role in mood regulation. Previous structural and functional brain imaging studies of the sgACC have revealed alterations of Gray Matter (GM) volumes and Blood Oxygenation Level Dependent signals (BOLD) in patients with Major Depressive Disorder (MDD) and Bipolar Disorder (BD), suggesting potential biomarker traits for affective disorders.

Method

In this study we investigated the gray matter volume of the sgACC in 3 different patient groups: 40 MDD patients, of which 20 were medicated (MDDm) and 20 were unmedicated (MDDu), and 21 medicated BD patients, and compared them with 23 healthy volunteers. We examined GM volume alteration using high-resolution 7T Magnetic Resonance Imaging (MRI) which produced quantitative maps of the spin-lattice relaxation time (T1). T1 maps provide high contrast between gray and white matter, and at 7 Tesla voxels with submillimeter resolution can be acquired in a reasonable scan time. We developed a semi-automatic segmentation protocol based on refined landmarks derived from previous volumetric studies using quantitative T1 maps as raw input data for automatic tissue segmentation of GM, WM and CSF (cerebrospinal fluid) tissue. The sgACC ROI was then superimposed on these tissue probability maps and traced manually by two independent raters (F.B., M.M.) following our semi-automatic segmentation protocol. Interrater reliability was calculated on a subset of 10 brain scans for each hemisphere, showing an Intra-Class Correlation coefficient (ICC) r = 0.96 for left sgACC and r = 0.84 for right sgACC respectively. In summary, we have developed a reproducible and reliable semi-automatic segmentation protocol to measure gray matter volume in the sgACC. Based on previous findings from meta-analyses on morphometric studies of the sgACC, we hypothesized that patients with MDD would have lower gray matter sgACC volumes compared to healthy subjects.

Results

Post-hoc analysis revealed smaller subgenual volumes for the left hemisphere in both the medicated (MDDm) and non-medicated (MDDu) group versus healthy controls (p = .001, p = .008) respectively. For the right hemisphere, the (MDDu) and BD group exhibited significantly lower subgenual volumes than healthy controls (p < .001, p = .004) respectively.

Conclusion

To our knowledge, this is the first morphometric MRI study using T1 maps obtained in high-resolution 7 Tesla MRI to compare MDD and BD patients with healthy controls.

Putative Risk Biomarkers of Bipolar Disorder in At-risk Youth

Bipolar disorder is a highly heritable and functionally impairing disease. The recognition and intervention of BD especially that characterized by early onset remains challenging. Risk biomarkers for predicting BD transition among at-risk youth may improve disease prognosis. We reviewed the more recent clinical studies to find possible pre-diagnostic biomarkers in youth at familial or (and) clinical risk of BD. Here we found that putative biomarkers for predicting conversion to BD include findings from multiple sample sources based on different hypotheses. Putative risk biomarkers shown by perspective studies are higher bipolar polygenetic risk scores, epigenetic alterations, elevated immune parameters, front-limbic system deficits, and brain circuit dysfunction associated with emotion and reward processing. Future studies need to enhance machine learning integration, make clinical detection methods more objective, and improve the quality of cohort studies.

Upstream and downstream pathways of diacylglycerol kinase : Novel phosphatidylinositol turnover-independent signal transduction pathways

Diacylglycerol kinase (DGK) phosphorylates diacylglycerol (DG) to produce phosphatidic acid (PA). Mammalian DGK comprise ten isozymes (α-κ) that regulate a wide variety of physiological and pathological events. Recently, we revealed that DGK isozymes use saturated fatty acid (SFA)/monosaturated fatty acid (MUFA)-containing and docosahexaenoic acid (22:6)-containing DG species, but not phosphatidylinositol (PI) turnover-derived 18:0/20:4-DG. For example, DGKδ, which is involved in the pathogenesis of type 2 diabetes, preferentially uses SFA/MUFA-containing DG species, such as 16:0/16:0- and 16:0/18:1-DG species, in high glucose-stimulated skeletal muscle cells. Moreover, DGKδ, which destabilizes the serotonin transporter (SERT) and regulates the serotonergic system in the brain, primarily generates 18:0/22:6-PA. Furthermore, 16:0/16:0-PA is produced by DGKζ in Neuro-2a cells during neuronal differentiation. We searched for SFA/MUFA-PA- and 18:0/22:6-PA-selective binding proteins (candidate downstream targets of DGKδ) and found that SFA/MUFA-PA binds to and activates the creatine kinase muscle type, an energy-metabolizing enzyme, and that 18:0/22:6-PA interacts with and activates Praja-1, an E3 ubiquitin ligase acting on SERT, and synaptojanin-1, a key player in the synaptic vesicle cycle. Next, we searched for SFA/MUFA-DG-generating enzymes upstream of DGKδ. We found that sphingomyelin synthase (SMS)1, SMS2, and SMS-related protein (SMSr) commonly act as phosphatidylcholine (PC)-phospholipase C (PLC) and phosphatidylethanolamine (PE)-PLC, generating SFA/MUFA-DG species, in addition to SMS and ceramide phosphoethanolamine synthase. Moreover, the orphan phosphatase PHOSPHO1 showed PC- and PE-PLC activities that produced SFA/MUFA-DG. Although PC- and PE-PLC activities were first described 70-35 years ago, their proteins and genes were not identified for a long time. We found that DGKδ interacts with SMSr and PHOSPHO1, and that DGKζ binds to SMS1 and SMSr. Taken together, these results strongly suggest that there are previously unrecognized signal transduction pathways that include DGK isozymes and generate and utilize SFA/MUFA-DG/PA or 18:0/22:6-DG/PA but not PI-turnover-derived 18:0/20:4-DG/PA.

Hypothalamic-pituitary-adrenal axis function in the offspring of parents with bipolar disorder and the impact of the family environment: A pilot study of the Reducing Unwanted Stress in the Home (RUSH) prevention program

BACKGROUND

The home environment of offspring of parents with bipolar disorder (OBD) has been characterized by high levels of stress and disorganization, which may impact development of the hypothalamic-pituitary-adrenal (HPA) axis and their subsequent risk for affective disorders. The present study examined the effects of a family-based preventative intervention on the OBD's HPA axis functioning and whether intervention-related changes in the home environment might have driven change in the HPA axis.

METHODS

Fifty-five children (6-11 years) were recruited from families having a parent with bipolar disorder (n=26) or families having two parents with no current mental disorders (n=29). Only those families with a parent having bipolar disorder participated in the preventative intervention. Both groups completed assessments at baseline, post-prevention, 3-, and 6-months post-prevention. At each assessment, family organization, control, cohesion, conflict, and expressiveness, in addition to childhood internalizing problems, were measured, and offspring saliva samples were collected across two consecutive days.

RESULTS

Hierarchical Linear Modelling found no significant differences in HPA axis functioning between groups at baseline or across time. Improvements in family organization, however, were associated with elevations in participants' cortisol awakening response (CAR; p =.004) and total daily output (p =.023), and a steepening of their diurnal slope (p =.003) across time. Similar findings were obtained for family cohesion with respect to CAR (p <.001) and, to a lesser degree, diurnal slope (p =.064).

DISCUSSION

HPA axis functioning did not differ between the OBD and healthy controls at baseline or in response to the preventative intervention. However, intervention-related improvements in family organization and, to a lesser degree, cohesion, were associated with adaptive changes in HPA functioning over time.

Arginine vasopressin in mood disorders: A potential biomarker of disease pathology and a target for pharmacologic intervention

Vasopressin or arginine-vasopressin (AVP) is a neuropeptide molecule known for its antidiuretic effects and serves to regulate plasma osmolality and blood pressure. The existing literature suggests that AVP plays a multifaceted-though less well-known-role in the central nervous system (CNS), particularly in relation to the pathophysiology and treatment of mood disorders. Animal models have demonstrated that AVP is implicated in regulating social cognition, affiliative and prosocial behaviors, and aggression, often in conjunction with oxytocin. In humans, AVP is implicated in mood disorders through its effects on the hypothalamic-pituitary-adrenal (HPA) axis as well as on the serotoninergic and glutamatergic systems. Measuring plasma AVP has yielded interesting but mixed results in mood and stress-related disorders. Recent advances have led to the development of copeptin as a stable and reliable surrogate biomarker for AVP. Another interesting but relatively unexplored issue is the interaction between the osmoregulatory system and mood disorder pathophysiology, given that psychotropic medications often cause dysregulation of AVP receptor expression or signaling that can subsequently lead to clinical syndromes like syndrome of inappropriate diuresis and diabetes insipidus. Finally, pharmaceutical trials of agents that act on V1a and V1b receptor antagonists are still underway. This narrative review summarizes: (1) the neurobiology of the vasopressinergic system in the CNS; (2) the interaction between AVP and the monoaminergic and glutamatergic pathways in the pathophysiology and treatment of mood disorders; (3) the iatrogenic AVP dysregulation caused by psychotropic medications; and (4) the pharmaceutical development of AVP receptor antagonists for the treatment of mood disorders.

Type 2 diabetes mellitus is associated with manic morbidity in elderly patients with mood disorders

The association between mood disorders, especially bipolar disorder (BD), and metabolic disorders, is long known. However, to which extent metabolic disorders affect the course of mood disorders in late life is still open to inquiring. To assess the impact of type 2 diabetes mellitus (T2DM) on late-life mood disorders a retrospective chart review was performed. Elderly depressive patients (≥ 65 years) diagnosed with Major Depressive Disorder (N = 57) or BD (N = 43) and followed up for at least 18 months were included and subdivided according to the presence of T2DM comorbidity. Vascular encephalopathy (39.1% vs. 15.6%, P  = 0.021) and neurocognitive disorders (21.7% vs. 5.2%, P  = 0.028), were more frequently reported in patients with T2DM than in those without. Patients with T2DM showed a greater percentage of follow-up time in manic episodes (r = -0.23, P  = 0.020) and a higher rate of manic episode(s) during follow-up (21.7% vs. 5.2%, P  = 0.028) than those without. When restricting longitudinal analyses to patients with bipolar spectrum disorders, results were confirmed. In line with the well-known connection between BD and metabolic disorders, our data support an association between T2DM and unfavorable course of illness in the elderly with BD.

Hypothalamic-pituitary-adrenal axis functioning in offspring of parents with a major affective disorder: a meta-analytic review

Because the offspring of parents with an affective disorder (OAD) are at high risk for developing mental disorders, and persons with an affective disorder (AD) show dysfunctional hypothalamic-pituitary-adrenal (HPA) axis activity, changes in HPA functioning in OAD might be an etiological risk factor that precedes the development of ADs. The primary aim of the meta-analysis was to quantitatively summarize the existing data on different indices of diurnal cortisol in the OAD. The secondary aim was to explore potential moderators of this relation. Following PRISMA guidelines, we included 26 studies (3052 offspring) on diurnal cortisol in our meta-analysis after an initial screening of 3408 articles. Intercept-only and meta-regression models were computed using the robust variance estimation method. Analyses examining mean cortisol levels at discrete timepoints, total cortisol output, and the cortisol rise in response to awakening (CAR) were conducted separately. The results demonstrated that the OAD had higher mean levels of cortisol at different timepoints throughout the day compared to controls (Hedge's g = 0.21). There was evidence of publication bias in studies examining CAR, such that effect sizes were positively biased. The present findings are consistent with a meta-analysis showing elevated cortisol in youth having an AD. Notable limitations across studies include the method of cortisol measurement and assessment of ADs. Altogether, these results highlight the fact that increased cortisol levels may act as a potential neuroendocrine antecedent and/or risk factor for the development of ADs among high risk youth.

Peripheral biomarkers to differentiate bipolar depression from major depressive disorder: a real-world retrospective study

BACKGROUND

Bipolar depression (BPD) is often misdiagnosed as a major depressive disorder (MDD) in clinical practice, which may be attributed to a lack of robust biomarkers indicative of differentiated diagnosis. This study analysed the differences in various hormones and inflammatory markers to explore peripheral biomarkers that differentiate BPD from MDD patients.

METHODS

A total of 2,048 BPD and MDD patients were included. A panel of blood tests was performed to determine the levels of sex hormones, stress hormones, and immune-related indicators. Propensity score matching (PSM) was used to control for the effect of potential confounders between two groups and further a receiver operating characteristic (ROC) curve was used to analyse the potential biomarkers for differentiating BPD from MDD.

RESULTS

Compared to patients with MDD, patients with BPD expressed a longer duration of illness, more hospitalisations within five years, and an earlier age of onset, along with fewer comorbid psychotic symptoms. In terms of biochemical parameters, MDD patients presented higher IgA and IgM levels, while BPD patients featured more elevated neutrophil and monocyte counts. ROC analysis suggested that combined biological indicators and clinical features could moderately distinguish between BPD and MDD. In addition, different biological features exist in BPD and MDD patients of different ages and sexes.

CONCLUSIONS

Differential peripheral biological parameters were observed between BPD and MDD, which may be age-sex specific, and a combined diagnostic model that integrates clinical characteristics and biochemical indicators has a moderate accuracy in distinguishing BPD from MDD.

The co-occurrence of multiple sclerosis and bipolar disorder: A case series on clinical and neuroimaging correlates

There is a dearth of studies on neuroimaging correlates of Bipolar Disorder (BD) in Multiple Sclerosis (MS). We describe the clinical profile and neuroimaging findings of four cases of MS with BD. Among them, two patients had multiple mood episodes preceding the neurological symptoms, one had concurrent manic and neurological symptoms, and one had multiple depressive episodes and an isolated steroid-induced manic episode. Frontal and temporal lobes, and Periventricular White Matter were involved in all four cases, and hence may be considered biological substrates of BD in MS. Larger studies are needed to validate the utility of these findings.

Postpartum symptoms of anxiety, depression and stress: differential relationships to women's cortisol profiles

PURPOSE

Women are at high risk of stress, anxiety, and depression during the postpartum but the ways in which these different types of psychological distress are related to cortisol regulation is not clear. We examined the distinct association of each type of distress with women's average cortisol level, cortisol awakening response (CAR), cortisol decline across the day (diurnal slope), and overall amount of cortisol secretion across the day (AUCG).

METHODS

At 6 months postpartum, a diverse group of 58 women completed measures of depression, anxiety, perceived stress, and life stressors. Each woman provided 4 salivary samples for cortisol assay from waking to bedtime on each of 2 consecutive days. Linear regressions were used to examine associations of stress, anxiety and depression to each of the 4 cortisol measures, controlling for number of stressful life events.

RESULTS

Depressive symptoms were associated with less of a rise in the CAR (β = -.46, p = 0.01), steeper diurnal slope (β = .51, p = 0.006), and higher average cortisol level (β = .42, p = .01). Women who met the clinical cutoff for an anxiety disorder had lower overall cortisol output (β = -.29, p = 0.03). Stress was not related to any cortisol metric.

CONCLUSIONS

Findings suggest that stress is less associated with cortisol alterations in the postpartum than are more severe types of psychological distress. Anxiety and depression may have distinct and opposite profiles of cortisol dysregulation. Results indicate that mental health assessment is critical even in the later postpartum so that interventions can be initiated to reduce emotional suffering and the risk of impaired cortisol regulation.

Global trends and hotspots in pain associated with bipolar disorder in the last 20 years: a bibliometric analysis

Purpose

The prevalence of comorbid pain and Bipolar Disorder in clinical practice continues to be high, with an increasing number of related publications. However, no study has used bibliometric methods to analyze the research progress and knowledge structure in this field. Our research is dedicated to systematically exploring the global trends and focal points in scientific research on pain comorbidity with bipolar disorder from 2003 to 2023, with the goal of contributing to the field.

Methods

Relevant publications in this field were retrieved from the Web of Science core collection database (WOSSCC). And we used VOSviewer, CiteSpace, and the R package "Bibliometrix" for bibliometric analysis.

Results

A total of 485 publications (including 360 articles and 125 reviews) from 66 countries, 1019 institutions, were included in this study. Univ Toront and Kings Coll London are the leading research institutions in this field. J Affect Disorders contributed the largest number of articles, and is the most co-cited journal. Of the 2,537 scholars who participated in the study, Stubbs B, Vancampfort D, and Abdin E had the largest number of articles. Stubbs B is the most co-cited author. "chronic pain," "neuropathic pain," "psychological pain" are the keywords in the research.

Conclusion

This is the first bibliometric analysis of pain-related bipolar disorder. There is growing interest in the area of pain and comorbid bipolar disorder. Focusing on different types of pain in bipolar disorder and emphasizing pain management in bipolar disorder are research hotspots and future trends. The study of pain related bipolar disorder still has significant potential for development, and we look forward to more high-quality research in the future.

Peripheral inflammation is associated with impaired sadness recognition in euthymic bipolar patients

BACKGROUND

Inflammation impairs cognitive function in healthy individuals and people with psychiatric disorders, such as bipolar disorder (BD). This effect may also impact emotion recognition, a fundamental element of social cognition. Our study aimed to investigate the relationships between pro-inflammatory cytokines and emotion recognition in euthymic BD patients and healthy controls (HCs).

METHODS

We recruited forty-four euthymic BD patients and forty healthy controls (HCs) and measured their inflammatory markers, including high-sensitivity C-reactive protein (hs-CRP), interleukin-6 (IL-6), and TNF-α. We applied validated cognitive tasks, the Wisconsin Card-Sorting Test (WCST) and Continuous Performance Test (CPT), and a social cognitive task for emotion recognition, Diagnostic Analyses of Nonverbal Accuracy, Taiwanese Version (DANVA-2-TW). We analyzed the relationships between cytokines and cognition and then explored possible predictive factors of sadness recognition accuracy.

RESULTS

Regarding pro-inflammatory cytokines, TNF-α was elevated in euthymic BD patients relative to HCs. In euthymic BD patients only, higher TNF-α levels were associated with lower accuracy of sadness recognition. Regression analysis revealed that TNF-α was an independent predictive factor of sadness recognition in patients with euthymic BD when neurocognition was controlled for.

CONCLUSIONS

We demonstrated that enhanced inflammation, indicated by increased TNF-α, was an independent predictive factor of impaired sadness recognition in BD patients but not in HCs. Our findings suggested a direct influence of TNF-α on sadness recognition and indicated vulnerability to depression in euthymic BD patients with chronic inflammation.

The relationship of neuropsychiatric symptoms with inflammatory markers in the hippocampus and cingulate cortex of bipolar disorder subjects: A post-mortem study

Increased levels of inflammation markers have been found in the peripheral tissue of individuals with bipolar disorder (BD), especially during mood episodes. Previous studies found distinctive inflammatory profiles across different brain regions, but potential associations with clinical symptoms are still lacking. This study aims to evaluate the association of neuropsychiatric symptoms with inflammatory markers in the hippocampus and cingulate of individuals with BD. Levels of IL-1β, IL-6, IL-17A, cortisol, and C-reactive protein (CRP) were measured in the hippocampus and anterior cingulate of 14 BD individuals and their non-psychiatric controls. Neuropsychiatric symptoms present in the three months before death were assessed using the Neuropsychiatric Inventory (NPI). In the BD group, greater NPI scores were associated with higher IL-6 in the hippocampus (p = 0.011) and cingulate (p = 0.038) and higher IL-1β (p = 0.039) in the hippocampus. After adjusting for age, sex and CDR, IL-1β and IL-6 were still associated with higher NPI in the hippocampus. In correlation analysis considering both BD and their controls, moderate positive associations were found between NPI and IL-6 and cortisol in the hippocampus (p < 0.001 and p = 0.006) and cingulate (p = 0.024 and p = 0.016), IL-1β (p < 0.001) and IL-17A in the hippocampus (p = 0.002). No difference in inflammatory markers was found according to type of psychotropic medication used. Hence, in individuals with BD, neuropsychiatric symptoms were differently associated with specific inflammatory cytokines and CRP in the hippocampus and cingulate. These results suggest that the neuroinflammatory changes occurring in BD may be more complex than previously expected and could be associated with clinical manifestations.

Targeting inflammasome complexes as a novel therapeutic strategy for mood disorders

INTRODUCTION

Inflammasome complexes, especially NLRP3, have gained great attention as a potential therapeutic target in mood disorders. NLRP3 triggers a caspase 1-dependent release of the inflammatory cytokines IL-1β and IL-18, and seems to interact with purinergic and kynurenine pathways, all of which are implicated in mood disorders development and progression.

AREAS COVERED

Emerging evidence supports NLRP3 inflammasome as a promising pharmacological target for mood disorders. We discussed the available evidence from animal models and human studies and provided a reflection on drawbacks and perspectives for this novel target.

EXPERT OPINION

Several studies have supported the involvement of NLRP3 inflammasome in MDD. However, most of the evidence comes from animal models. The role of NLRP3 inflammasome in BD as well as its anti-manic properties is not very clear and requires further exploration. There is evidence of anti-manic effects of P2×R7 antagonists associated with reduction in the brain levels of IL-1β and TNF-α in a murine model of mania. The involvement of other NLRP3 inflammasome expressing cells besides microglia, like astrocytes, and of other inflammasome complexes in mood disorders also deserves further investigation. Preclinical and clinical characterization of NLRP3 and other inflammasomes in mood disorders is needed before considering translational approaches, including clinical trials.

Hypothalamic Subunit Volumes in Schizophrenia and Bipolar Spectrum Disorders

BACKGROUND

The hypothalamus is central to many hormonal and autonomous nervous system pathways. Emerging evidence indicates that these pathways may be disrupted in schizophrenia and bipolar disorder. Yet, few studies have examined the volumes of hypothalamic subunits in these patient groups. We compared hypothalamic subunit volumes in individuals with psychotic disorders to healthy controls.

STUDY DESIGN

We included 344 patients with schizophrenia spectrum disorders (SCZ), 340 patients with bipolar disorders (BPD), and 684 age- and-sex-matched healthy controls (CTR). Total hypothalamus and five hypothalamic subunit volumes were extracted from T1-weighted magnetic resonance imaging (MRI) using an automated Bayesian segmentation method. Regression models, corrected for age, age2, sex, and segmentation-based intracranial volume (sbTIV), were used to examine diagnostic group differences, interactions with sex, and associations with clinical symptoms, antipsychotic medication, antidepressants and mood stabilizers.

STUDY RESULTS

SCZ had larger volumes in the left inferior tubular subunit and smaller right anterior-inferior, right anterior-superior, and right posterior hypothalamic subunits compared to CTR. BPD did not differ significantly from CTR for any hypothalamic subunit volume, however, there was a significant sex-by-diagnosis interaction. Analyses stratified by sex showed smaller right hypothalamus and right posterior subunit volumes in male patients, but not female patients, relative to same-sex controls. There was a significant association between BPD currently taking antipsychotic medication and the left inferior tubular subunits volumes.

CONCLUSIONS

Our results show regional-specific alterations in hypothalamus subunit volumes in individuals with SCZ, with relevance to HPA-axis dysregulation, circadian rhythm disruption, and cognition impairment.

Implications of Kynurenine Pathway Metabolism for the Immune System, Hypothalamic-Pituitary-Adrenal Axis, and Neurotransmission in Alcohol Use Disorder

In recent years, there has been a marked increase in interest in the role of the kynurenine pathway (KP) in mechanisms associated with addictive behavior. Numerous reports implicate KP metabolism in influencing the immune system, hypothalamic-pituitary-adrenal (HPA) axis, and neurotransmission, which underlie the behavioral patterns characteristic of addiction. An in-depth analysis of the results of these new studies highlights interesting patterns of relationships, and approaching alcohol use disorder (AUD) from a broader neuroendocrine-immune system perspective may be crucial to better understanding this complex phenomenon. In this review, we provide an up-to-date summary of information indicating the relationship between AUD and the KP, both in terms of changes in the activity of this pathway and modulation of this pathway as a possible pharmacological approach for the treatment of AUD.

Use of gene regulatory network analysis to repurpose drugs to treat bipolar disorder

BACKGROUND

Bipolar disorder (BD) presents significant challenges in drug discovery, necessitating alternative approaches. Drug repurposing, leveraging computational techniques and expanding biomedical data, holds promise for identifying novel treatment strategies.

METHODS

This study utilized gene regulatory networks (GRNs) to identify significant regulatory changes in BD, using network-based signatures for drug repurposing. Employing the PANDA algorithm, we investigated the variations in transcription factor-GRNs between individuals with BD and unaffected individuals, incorporating binding motifs, protein interactions, and gene co-expression data. The differences in edge weights between BD and controls were then used as differential network signatures to identify drugs potentially targeting the disease-associated gene signature, employing the CLUEreg tool in the GRAND database.

RESULTS

Using a large RNA-seq dataset of 216 post-mortem brain samples from the CommonMind consortium, we constructed GRNs based on co-expression for individuals with BD and unaffected controls, involving 15,271 genes and 405 TFs. Our analysis highlighted significant influences of these TFs on immune response, energy metabolism, cell signalling, and cell adhesion pathways in the disorder. By employing drug repurposing, we identified 10 promising candidates potentially repurposed as BD treatments.

LIMITATIONS

Non-drug-naïve transcriptomics data, bulk analysis of BD samples, potential bias of GRNs towards well-studied genes.

CONCLUSIONS

Further investigation into repurposing candidates, especially those with preclinical evidence supporting their efficacy, like kaempferol and pramocaine, is warranted to understand their mechanisms of action and effectiveness in treating BD. Additionally, novel targets such as PARP1 and A2b offer opportunities for future research on their relevance to the disorder.

Longitudinal hair cortisol in bipolar disorder and a mechanism based on HPA dynamics

Bipolar disorder (BD) is marked by fluctuating mood states over months to years, often with elevated cortisol levels. Elevated cortisol can also trigger mood episodes. Here, we combine longitudinal hair cortisol and mood measurements with mathematical modeling to provide a potential mechanistic link between cortisol and mood timescales in BD. Using 12 cm hair samples, representing a year of growth, we found enhanced year-scale cortisol fluctuations whose amplitude averaged 4-fold higher in BD (n = 26) participants than controls (n = 59). The proximal 2 cm of hair correlated with recent mood scores. Depression (n = 266) and mania (n = 273) scores from a longitudinal study of BD showed similar frequency spectra. These results suggest a mechanism for BD in which high emotional reactivity excites the slow timescales in the hypothalamic-pituitary-adrenal (HPA) axis to generate elevated months-scale cortisol fluctuations, triggering cortisol-induced mood episodes.

Steroid-induced mania in a patient with previously well-controlled organic bipolar 1-like affective disorder secondary to acquired brain injury: case report and literature review

Steroid-induced neuropsychiatric sequelae are common, and pose significant risks to people usually receiving glucocorticoids in the context of physical illness. Steroid-induced mania and hypomania are the most common of the acute complications, yet despite great progress in understandings in neurophysiology there are no recent studies which review the factors which might predict who will experience this severe complication, nor are there consensus guidelines on management. We report the unusual case of a woman in her 50s admitted to a psychiatric unit with steroid-induced mania despite compliance with two mood stabilisers, several days after the administration of a Dexamethasone and Docetaxel chemotherapy regime adjunctive to lumpectomy for breast cancer. She had previously been diagnosed with an organic affective disorder (with classical bipolar 1 pattern) following severe ventriculitis related to ventricular drain insertion for obstructive hydrocephalus secondary to a colloid cyst. She had no psychiatric illness before this brain injury, but has a maternal history of idiopathic bipolar 1 affective disorder. Her episode of steroid-induced mania resolved following use of sedative medications, continuation of her existing mood stabilisers, and reductions of the steroid dosing in collaboration with her oncology team, which also protected her from further manic relapses during continued chemotherapy. Established mental illness, a family history, and acquired brain injury may reflect risk factors for steroid-induced mania through currently unclear pathways. Future epidemiological studies could better confirm these observations, and basic neuroscience may look to further explore the role of extrinsic glucocorticoids in the pathophysiology of affective disorders.

The effect of neuroendocrine abnormalities on the risk of psychiatric readmission after hospitalization for bipolar disorder: A retrospective study

BACKGROUND

The correlation between the endocrine system and bipolar disorder(BD) has been well recognized, yet the influence of neuroendocrine hormones on readmission risk post-hospitalization for BD remains largely unexplored. This retrospective cohort study was to scrutinize the impact of neuroendocrine functionality on the readmission of patients with BD post-hospitalization for mental disorders.

METHODS

The dataset was derived from the electronic medical records of the First Affiliated Hospital of Jinan University in Guangzhou, China. Both univariate and multivariate logistic regression analysis were conducted on all patients hospitalized for BD, and from 1 January 2017 to October 2022.

RESULTS

Of the 1110 eligible patients, 83 and 141 patients experienced psychiatric readmissions within 90 and 180 days post-discharge, respectively. Multivariate analysis revealed that high serum TSH levels (aOR = 1.079; 95%CI = 1.003-1.160) and thyroid disease comorbidities (aOR = 2.899; 95%CI = 1.303-6.452) were independently correlated with the risk of 90-day readmission; while increased serum TSH levels (aOR = 1.179; 95%CI = 1.081-1.287) represented a risk factor for 180-day readmission. These results indicate that high serum TSH levels and thyroid disease comorbidities may contribute to an elevated readmission risk in patients with BD following hospitalization.

CONCLUSION

Routinely evaluating and intervening in thyroid function is crucial in the treatment of BD, as it may aid in preventing re-hospitalization.

Ghrelin and depressive symptoms in patients with first-episode drug-naïve major depressive disorder: The mediating role of hypothalamic-pituitary-adrenal axis

BACKGROUND

Major depressive disorder (MDD) is one of the global burdens of disease, and its pathogenesis remains unclear. An increasing amount of research indicates that ghrelin regulates mood in patients with MDD. Still, current results are inconsistent, and the mechanisms underlying how ghrelin modulates depressive symptoms are inconclusive, especially in first-episode drug-naïve MDD patients. Therefore, this study aims to investigate the relationship and potential mechanism between ghrelin and first-episode drug-naïve MDD.

METHODS

Ninety first-episode drug-naïve MDD patients and 65 healthy controls (HCs) were included. Hamilton Depression Scale (HAMD-17) as a measure of depressive symptoms. Plasma levels of ghrelin and hypothalamic-pituitary-adrenal axis (HPA-axis) hormones were measured in all participants.

RESULTS

Compared to HCs, the ghrelin levels were higher in the MDD (p < .001) and still showed significance after covarying for sex, age, and Body Mass Index (BMI). Ghrelin was positively related to corticotropin-releasing-hormone (CRH) levels (r = .867, p < .001), adrenocorticotropic hormone (ACTH) levels (r = .830, p < .001), and cortisol levels (r = .902, p < .001) in partial correlation analysis. In addition, there was a positive correlation between HAMD total score and ghrelin levels (r = .240, p = .026). Other than that, the HAMD total score also had a positive correlation with the CRH (r = .333, p = .002) and cortisol (r = .307, p = .004) levels. Further mediation analysis demonstrated that the relationship between ghrelin and HAMD total score was mediated by CRH (ab-path; β = .4457, 95% CI = 0.0780-1.0253, c-path; β = .2447, p = .0260, c'-path; β = -.2009, p = .3427).

CONCLUSIONS

These findings revealed that plasma ghrelin provides a pivotal link to depressive symptoms in first-episode drug-naive MDD patients. CRH mediated the relationship between ghrelin and HAMD total score. It might provide new insights into understanding the pathogenesis of MDD, contributing to intervention and treatment from this approach.

Feasibility of Identifying Factors Related to Alzheimer's Disease and Related Dementia in Real-World Data

A comprehensive view of factors associated with AD/ADRD will significantly aid in studies to develop new treatments for AD/ADRD and identify high-risk populations and patients for prevention efforts. In our study, we summarized the risk factors for AD/ADRD by reviewing existing meta-analyses and review articles on risk and preventive factors for AD/ADRD. In total, we extracted 477 risk factors in 10 categories from 537 studies. We constructed an interactive knowledge map to disseminate our study results. Most of the risk factors are accessible from structured Electronic Health Records (EHRs), and clinical narratives show promise as information sources. However, evaluating genomic risk factors using RWD remains a challenge, as genetic testing for AD/ADRD is still not a common practice and is poorly documented in both structured and unstructured EHRs. Considering the constantly evolving research on AD/ADRD risk factors, literature mining via NLP methods offers a solution to automatically update our knowledge map.

Genetic signatures of suicide attempt behavior: insights and applications

INTRODUCTION

Every year about 800,000 complete suicide events occur. The identification of biologic markers to identify subjects at risk would be helpful in targeting specific support treatments.

AREA COVERED

A narrative review defines the meta-analytic level of current evidence about the biologic markers of suicide behavior (SB). The meta-analytic evidence gathered so far indicates that the hypothesis-driven research largely failed to identify the biologic markers of suicide. The most consistent and replicated result was reported for: 1) 5-HTR2A T102C, associated with SB in patients with schizophrenia (OR = 1.73 (1.11-2.69)) and 2) BDNF Val66Met (rs6265), with the Met-Val + Val-Val carriers found to be at risk for suicide in the Caucasian population (OR: 1.96 (1.58-2.43)), while Val-Val vs. Val-Met + Met carriers found to be at risk for suicide in the Asian populations (OR: 1.36 (1.04-1.78)). GWAS-based meta-analyses indicate some positive replicated findings regarding the DRD2, Neuroligin gene, estrogen-related genes, and genes involved in gene expression.

EXPERT OPINION

Most consistent results were obtained when analyzing sub-samples of patients. Some promising results come from the implementation of the polygenic risk score. There is no current consensus about an implementable biomarker for SB.

A genome-wide association study of antidepressant-induced mania

Antidepressant-induced mania (AIM) is a side effect of antidepressant treatment that is characterized by mania or hypomania after the start of medication. It is likely polygenic, but its genetic component remains largely unexplored. We aim to conduct the first genome-wide association study of AIM in 814 bipolar disorder patients of European ancestry. We report no significant findings from our single-marker or gene-based analyses. Our polygenic risk score analyses also did not yield significant results with bipolar disorder, antidepressant response, or lithium response. Our suggestive findings on the hypothalamic-pituitary-adrenal axis and the opioid system in AIM require independent replications.

Bipolar mania and epilepsy pathophysiology and treatment may converge in purine metabolism: A new perspective on available evidence

Decreased ATPergic signaling is an increasingly recognized pathophysiology in bipolar mania disease models. In parallel, adenosine deficit is increasingly recognized in epilepsy pathophysiology. Under-recognized ATP and/or adenosine-increasing mechanisms of several antimanic and antiseizure therapies including lithium, valproate, carbamazepine, and ECT suggest a fundamental pathogenic role of adenosine deficit in bipolar mania to match the established role of adenosine deficit in epilepsy. The depletion of adenosine-derivatives within the purine cycle is expected to result in a compensatory increase in oxopurines (uric acid precursors) and secondarily increased uric acid, observed in both bipolar mania and epilepsy. Cortisol-based inhibition of purine conversion to adenosine-derivatives may be reflected in observed uric acid increases and the well-established contribution of cortisol to both bipolar mania and epilepsy pathology. Cortisol-inhibited conversion from IMP to AMP as precursor of both ATP and adenosine may represent a mechanism for treatment resistance common in both bipolar mania and epilepsy. Anti-cortisol therapies may therefore augment other treatments both in bipolar mania and epilepsy. Evidence linking (i) adenosine deficit with a decreased need for sleep, (ii) IMP/cGMP excess with compulsive hypersexuality, and (iii) guanosine excess with grandiose delusions may converge to suggest a novel theory of bipolar mania as a condition characterized by disrupted purine metabolism. The potential for disease-modification and prevention related to adenosine-mediated epigenetic changes in epilepsy may be mirrored in mania. Evaluating the purinergic effects of existing agents and validating purine dysregulation may improve diagnosis and treatment in bipolar mania and epilepsy and provide specific targets for drug development.

Suicidality and its associated factors among mood disorder patients in emergency department in China: a comparative study using propensity score matching approach

Suicidality in mood disorder patients is common, especially in emergency department (ED), but the patterns and associated factors of suicidality are not clear. This study compared biomarkers and mental health symptoms (i.e., depression, anxiety, and psychiatric symptoms) between mood disorder patients with and without the whole range of suicidality comprising suicidal ideation (SI), suicide plan (SP), and suicide attempt (SA). This cross-sectional, comparative, convenient-sampling study was conducted between January 2021 and March 2022, in emergency department of Beijing Anding Hospital, China. Patients with mood disorders at a psychiatric emergency department were assessed, with measurements of suicidality, biomarkers, depressive, anxiety, and psychiatric symptoms were assessed using the 24 items-Hamilton Depression Rating Scale (HAMD-24), Hamilton Anxiety Rating Scale (HAMA), Young Manic Rating Scale (YMRS) and Brief Psychiatric Rating Scale (BPRS), respectively. The propensity score matching (PSM) method was used to identify patients in mood disorder with and without SI, SP, and SA. A generalized linear model (GLM) was used to assess the differences in biomarkers, depressive, anxiety, and psychiatric symptoms between patients in mood disorder with and without SI, SP, and SA. In total, 898 participated in this survey and completed the assessment. Illness duration was significantly negatively associated with SA (OR = 0.969, 95%CI = 0.939-0.999, P = 0.046). HAMD-24 total score was significantly positively associated with the SI (OR = 1.167, 95%CI = 1.134-1.201, p < 0.001), SP (OR = 1.159, 95%CI = 1.126-1.192, p < 0.001) and SA (OR = 1.189, 95%CI = 1.144-1.235, p < 0.001) of the matched samptched sample. However, YMRS total score was significantly negatively associated with the SI (OR = 0.928, 95%CI = 0.905-0.951, p < 0.001), SP (OR = 0.920, 95%CI = 0.897-0.944, p < 0.001) and SA (OR = 0.914, 95%CI = 0.890-0.938, p < 0.001) of the matched sample after adjusting for age, gender, marital status, and occupation. The duration of illness, severity of depressive symptoms and severity of manic symptoms appeared to be more likely to influence suicidality. Considering the significant risk of suicide in mood disorders on psychiatric emergency care, timely treatment and effective management of suicidality in this population group need to be developed.

Acute effects of mifepristone on emotional processing related brain activity: A functional MRI study

The Hypothalamic-pituitary-adrenal (HPA) axis plays an important role in the pathophysiology of mood disorders, and preliminary data suggests that glucocorticoid receptor (GR) antagonism may be an important therapeutic mechanism. The effects of modulating HPA axis function on emotional processing related brain activity, which may be abnormal in depressed mood, is poorly understood. This study used a pharmacological functional magnetic resonance imaging (fMRI) design to determine the effects of the GR and progesterone receptor antagonist mifepristone on emotional faces processing task related brain activations in 19 right-handed healthy male participants. Each participant received 600 mg mifepristone or placebo on two separate imaging days and then performed an emotional processing fMRI task four hours later. The effect of mifepristone on task related brain activations was determined using Region-of-Interest (ROI) analyses and an exploratory whole brain voxel-wise analyses. No significant changes were observed in the defined ROIs (amygdala, anterior cingulate cortex, insula) or in the exploratory whole brain analyses that was associated with mifepristone administration in either the angry vs happy faces or angry and happy faces vs implicit baseline contrasts. Task reaction times and accuracy were similar in both mifepristone and placebo conditions (all p > 0.05). Our study failed to show significant evidence of modulation of emotional processing related brain activity associated with acute mifepristone administration. Future research should use fMRI to investigate the longer-term administration effects of mifepristone on mood in healthy participants and people with mood disorders to provide a deeper understanding of the potential effects on depressive symptoms.

Alterations in pituitary adenylate cyclase-activating polypeptide in major depressive disorder, bipolar disorder, and comorbid depression in Alzheimer's disease in the human hypothalamus and prefrontal cortex

BACKGROUND

Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) is involved in the stress response and may play a key role in mood disorders, but no information is available on PACAP for the human brain in relation to mood disorders.

METHODS

PACAP-peptide levels were determined in a major stress-response site, the hypothalamic paraventricular nucleus (PVN), of people with major depressive disorder (MDD), bipolar disorder (BD) and of a unique cohort of Alzheimer's disease (AD) patients with and without depression, all with matched controls. The expression of PACAP-(Adcyap1mRNA) and PACAP-receptors was determined in the MDD and BD patients by qPCR in presumed target sites of PACAP in stress-related disorders, the dorsolateral prefrontal cortex (DLPFC) and anterior cingulate cortex (ACC).

RESULTS

PACAP cell bodies and/or fibres were localised throughout the hypothalamus with differences between immunocytochemistry and in situ hybridisation. In the controls, PACAP-immunoreactivity-(ir) in the PVN was higher in women than in men. PVN-PACAP-ir was higher in male BD compared to the matched male controls. In all AD patients, the PVN-PACAP-ir was lower compared to the controls, but higher in AD depressed patients compared to those without depression. There was a significant positive correlation between the Cornell depression score and PVN-PACAP-ir in all AD patients combined. In the ACC and DLPFC, alterations in mRNA expression of PACAP and its receptors were associated with mood disorders in a differential way depending on the type of mood disorder, suicide, and psychotic features.

CONCLUSION

The results support the possibility that PACAP plays a role in mood disorder pathophysiology.

Hippocampal Dynamic Functional Connectivity, HPA Axis Activity, and Personality Trait in Bipolar Disorder with Suicidal Attempt

INTRODUCTION

Suicide in bipolar disorder (BD) is a multifaceted behavior, involving specific neuroendocrine and psychological mechanisms. According to previous studies, we hypothesized that suicidal BD patients may exhibit impaired dynamic functional connectivity (dFC) variability of hippocampal subregions and hypothalamic-pituitary-adrenal (HPA) axis activity, which may be associated with suicide-related personality traits. The objective of our study was to clarify this.

METHODS

Resting-state functional magnetic resonance imaging data were obtained from 79 patients with BD, 39 with suicidal attempt (SA), and 40 without SA, and 35 healthy controls (HCs). The activity of the HPA axis was assessed by measuring morning plasma adrenocorticotropic hormone (ACTH) and cortisol (CORT) levels. All participants underwent personality assessment using Minnesota Multiphasic Personality Inventory-2 (MMPI-2).

RESULTS

BD patients with SA exhibited increased dFC variability between the right caudal hippocampus and the left superior temporal gyrus (STG) when compared with non-SA BD patients and HCs. BD with SA also showed significantly lower ACTH levels in comparison with HCs, which was positively correlated with increased dFC variability between the right caudal hippocampus and the left STG. BD with SA had significantly higher scores of Hypochondriasis, Depression, and Schizophrenia than non-SA BD. Additionally, multivariable regression analysis revealed the interaction of ACTH × dFC variability between the right caudal hippocampus and the left STG independently predicted MMPI-2 score (depression evaluation) in suicidal BD patients.

CONCLUSION

These results suggested that suicidal BD exhibited increased dFC variability of hippocampal-temporal cortex and less HPA axis hyperactivity, which may affect their personality traits.

Long-term exposure to ambient air pollution, genetic susceptibility, and the incidence of bipolar disorder: A prospective cohort study

There is mounting recent evidence showing that air pollution exposure may be related to the risk of mental health, yet the association between long-term exposure to air pollution and the risk of incident bipolar disorder (BD) remains unclear. Thus we aim to identify associations between air pollution and the incidence of BD in a prospective population-based cohort. In total, 482,726 participants who were free of BD from the UK Biobank were included in this prospective study. We applied time-varying Cox proportional hazards models, accounting for relevant confounders, and used annual-year moving averages of air pollution as time-varying exposures. The genetic risk for BD was categorized into three categories (low, intermediate, and high) according to the tertiles of polygenic risk score. During a median of 10.79-year follow-up, 923 incident BD events were recorded. Long-term exposures to PM2.5, PM10, NO2, and NOx were associated with increased BD risk. Estimated HRs (95% CIs) for each interquartile range increase in PM2.5, PM10, NO2, and NOx concentrations were 1.31 (1.18-1.45), 1.19 (1.09-1.31), 1.19 (1.08-1.30), and 1.16 (1.07-1.26), respectively. Associations were still observed and even stronger at pollutant concentrations lower than WHO air quality guideline. In subgroup analysis stratified by genetic risk, we observed consistent associations between all pollutants and BD risk in intermediate and high genetic risk groups, but not in low genetic risk group. For example, the HRs (95% CIs) for PM2.5 were 1.00 (0.94-1.53), 1.30 (1.06-1.59), and 1.34 (1.16-1.54) in low, intermediate, and high genetic groups, respectively. In conclusion, long-term exposure to air pollution was significantly associated with an elevated risk of BD. Associations of air pollution with BD occurred only within intermediate and high genetic risk categories and were even stronger at the pollutants levels below WHO air quality guidelines. These findings could help inform policy makers regarding ambient air quality standards and BD management.

Predicting the diagnosis of various mental disorders in a mixed cohort using blood-based multi-protein model: a machine learning approach

The lack of objective diagnostic methods for mental disorders challenges the reliability of diagnosis. The study aimed to develop an easily accessible and useable objective method for diagnosing major depressive disorder (MDD), schizophrenia (SZ), bipolar disorder (BPD), and panic disorder (PD) using serum multi-protein. Serum levels of brain-derived neurotrophic factor (BDNF), VGF (non-acronymic), bicaudal C homolog 1 (BICC1), C-reactive protein (CRP), and cortisol, which are generally recognized to be involved in different pathogenesis of various mental disorders, were measured in patients with MDD (n = 50), SZ (n = 50), BPD (n = 55), and PD along with 50 healthy controls (HC). Linear discriminant analysis (LDA) was employed to construct a multi-classification model to classify these mental disorders. Both leave-one-out cross-validation (LOOCV) and fivefold cross-validation were applied to validate the accuracy and stability of the LDA model. All five serum proteins were included in the LDA model, and it was found to display a high overall accuracy of 96.9% when classifying MDD, SZ, BPD, PD, and HC groups. Multi-classification accuracy of the LDA model for LOOCV and fivefold cross-validation (within-study replication) reached 96.9 and 96.5%, respectively, demonstrating the feasibility of the blood-based multi-protein LDA model for classifying common mental disorders in a mixed cohort. The results suggest that combining multiple proteins associated with different pathogeneses of mental disorders using LDA may be a novel and relatively objective method for classifying mental disorders. Clinicians should consider combining multiple serum proteins to diagnose mental disorders objectively.

Folic acid does not have an anti-manic effect but protect the brain against oxidative stress in an animal model of mania induced by ouabain

BACKGROUND

Bipolar disorder (BD) is a complex and severe mental disorder that affects 1-3 % of the world population. Studies have suggested the involvement of oxidative stress in the physiopathology of this psychiatry disorder. Folic acid (FA), a vitamin from the B complex, is a nutraceutical that has recently been researched as a possible treatment for BD since folate is reduced in patients with the disorder. The present study aimed to evaluate the effects of lithium (Li) and FA on behavioral changes and oxidative stress parameters in an animal model of mania induced by ouabain (OUA).

METHODS

Wistar rats received a single intracerebroventricular (ICV) injection of OUA or artificial cerebrospinal fluid (aCSF). From the day following ICV injection, the rats were treated for seven days with gavage injections of Li (47.5 mg/kg/mL), FA (50 mg/kg/mL), or water (1 mL/kg). On the 7th day after OUA injection, locomotor activity was measured using the open-field test. In addition, the oxidative stress parameters were evaluated in rats' frontal cortex, striatum, and hippocampus.

RESULTS

OUA induced mania-like behavior and oxidative stress in rats' brains, but Li could reverse these alterations. FA did not affect behavior parameters; however, it presents an antioxidant effect on the brain structures evaluated.

LIMITATIONS

The study was only evaluated male rats and ICV injection is an invasive procedure.

CONCLUSION

These results indicate that even though FA has an effect against the oxidative stress induced by OUA, this effect was not strong enough to interfere with behavior parameters.

Microbiota-gut-brain axis mechanisms in the complex network of bipolar disorders: potential clinical implications and translational opportunities

Bipolar disorders (BD) represent a severe leading disabling mental condition worldwide characterized by episodic and often progressive mood fluctuations with manic and depressive stages. The biological mechanisms underlying the pathophysiology of BD remain incompletely understood, but it seems that there is a complex picture of genetic and environmental factors implicated. Nowadays, gut microbiota is in the spotlight of new research related to this kind of psychiatric disorder, as it can be consistently related to several pathophysiological events observed in BD. In the context of the so-called microbiota-gut-brain (MGB) axis, it is shown to have a strong influence on host neuromodulation and endocrine functions (i.e., controlling the synthesis of neurotransmitters like serotonin or mediating the activation of the hypothalamic-pituitary-adrenal axis), as well as in modulation of host immune responses, critically regulating intestinal, systemic and brain inflammation (neuroinflammation). The present review aims to elucidate pathophysiological mechanisms derived from the MGB axis disruption and possible therapeutic approaches mainly focusing on gut microbiota in the complex network of BD. Understanding the mechanisms of gut microbiota and its bidirectional communication with the immune and other systems can shed light on the discovery of new therapies for improving the clinical management of these patients. Besides, the effect of psychiatric drugs on gut microbiota currently used in BD patients, together with new therapeutical approaches targeting this ecosystem (dietary patterns, probiotics, prebiotics, and other novelties) will also be contemplated.

Hormonal and inflammatory signatures of different mood episodes in bipolar disorder: a large-scale clinical study

BACKGROUND

Bipolar disorder (BD) is characterized by intensive mood fluctuations. While hormones imbalance plays important role in the mood swings, it is unknown whether peripheral hormones profiles could differentiate the manic and depressive mood episodes in BD. In this study, we investigated the changes of various hormones and inflammatory markers across distinct mood episodes of BD in a large clinical study to provide mood episode-specific peripheral biomarkers for BD.

METHODS

A total of 8332 BD patients (n = 2679 depressive episode; n = 5653 manic episode) were included. All patients were in acute state of mood episodes and need hospitalization. A panel of blood tests were performed for levels of sex hormones (serum levels of testosterone, estradiol, and progesterone), stress hormones (adrenocorticotropic hormone and cortisol), and an inflammation marker (C-reactive protein, CRP). A receiver operating characteristic (ROC) curve was used to analyze the discriminatory potential of the biomarkers for mood episodes.

RESULTS

In overall comparison between mood episodes, the BD patients expressed higher levels of testosterone, estradiol, progesterone, and CRP (P < 0.001) and lower adrenocorticotropic hormone (ACTH) level (P < 0.001) during manic episode. The episode-specific changes of testosterone, ACTH, and CRP levels remained between the two groups (P < 0.001) after correction for the confounding factors including age, sex, BMI, occupation, marital status, tobacco use, alcohol consumption, psychotic symptoms, and age at onset. Furthermore, we found a sex- and age-specific impact of combined biomarkers in mood episodes in male BD patients aged ≥ 45 years (AUC = 0.70, 95% CI, 0.634-0.747), not in females.

CONCLUSIONS

While both hormone and inflammatory change is independently associated with mood episodes, we found that the combination of sex hormones, stress hormones and CRP could be more effective to differentiate the manic and depressive episode. The biological signatures of mood episodes in BD patients may be sex- and age-specific. Our findings not only provide mood episode-related biological markers, but also better support for targeted intervention in BD treatments.

Gene-environment interaction between HPA-axis genes and trauma exposure in the suicide behavior: A systematic review

Suicide behavior (SB) emerge from complex interactions among traumatic events and multiple genetic factors. We conducted the first systematic review to assess the evidence of a link among trauma exposure, HPA-axis genes, and SB. A systematic search of PubMed, EBSCO, Science Direct, PsychInfo, and Scopus databases on gene-environment interaction, and susceptibility to SB was carried out until February 2022. Our study was prospectively registered in PROSPERO (CRD42022316141). A total of 13 epidemiological studies (11,756 subjects) were included: eight studies focused on traumatic experiences in the childhood and five studies on lifetime trauma exposure. All studies reported a positive association between the trauma exposure with SB. Gene-environment interaction was reported for CRHR1 (n = 6), CRHR2 (n = 2), FKBP5 (n = 2), and CRHBP (n = 1), however, for CRH, NR3C1, MC2R, and POMC genes no found gene-environment effects on SB. Trauma exposure could be one mechanism that links HPA-axis genes activity with the development of SB.

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.

A systematic review on gut-brain axis aberrations in bipolar disorder and methods of balancing the gut microbiota

BACKGROUND

Bipolar disorder (BD) is a mood disorder that affects millions worldwide. Up to half of the diagnosed patients are reported to not receive adequate treatment. This study aims to assess the relationship between the gut-brain axis and BD and to discuss and compare the efficacy of varying methods of balancing gut microbiotas in BD.

METHODS

Using PubMed, Embase, and Google Scholar from November 2021 to February 2022, we found 5310 studies on gut microbiota and its relation to BD. Using our inclusion criteria, 5283 studies were excluded. A total of 27 full-text articles were assessed for eligibility. Also, 12 articles that met our criteria and eligibility criteria reported on 613 BD patients.

RESULTS

Most studies analyzed found an overall difference in gut microbiota composition in bipolar patients compared to healthy controls, though the alterations found were not consistent. Differences in Lactobacillus, Faecalibacterium, and Ruminococcus abundance in BD compared to controls were found to be the most consistent across a few of the studies, but their effects on the gut-brain axis conflicted. Probiotic supplementation was found to lower patient rehospitalizations and significantly improve depressive symptoms and cognitive impairments among patients with BD.

CONCLUSIONS

Multiple studies included in this review point toward a possible link between BD and the gut microbiota. Probiotic supplements and other gut-balancing therapies could serve as effective adjunctive methods for the treatment of BD. Notable limitations of the studies included for analysis were small sample sizes and majority observational study designs. Furthermore, the microbiota aberrations found in patients with BD were not consistent across multiple studies. Despite these limitations, our findings demonstrate the need for further research regarding the relationship between aberrant gut microbiota profiles and BD, as well as the effectiveness of gut balancing methods as adjunctive treatments.

Is a Genetic Variant associated with Bipolar Disorder Frequent in People without Bipolar Disorder but with Characteristics of Hyperactivity and Novelty Seeking?

Objective

The objective is to verify whether a genetic condition associated with bipolar disorder (BD) is frequent in old adults adapted to their environment, without BD, but with aptitudes for hyperactivity and novelty seeking (H/NS).

Methods

In this cross-sectional study, the study sample included healthy elderly people (40 participants, aged 60 or older) living in an urban area and recruited from a previous study on physical exercise and active aging, who were compared with 21 old adults with BD from the same area. The genetic methodology consisted of blood sampling, DNA extraction, real-time PCR jointly with FRET probes, and the SANGER sequencing method. The genetic variant RS1006737 of CACNA1C, found to be associated with bipolar disorder diagnosis, was investigated.

Results

The frequency of the RS1006737 genetic variant in the study group (H/NS) is not higher than in the BD group and is statistically significantly higher than in all the control groups found in the literature. However, the familiarity for BD is higher in old adults with BD than in the H/NS sample without BD. The risk of BD in the family (also considering those without BD but with family members with BD) is not associated with the presence of the genetic variant examined.

Conclusion

The study suggests that the gene examined is associated with characteristics of hyperactivity rather than just BD. Nevertheless, choosing to participate in an exercise program is an excessively general way to identify H/NS. The next step would be to identify the old adults with well-defined H/NS features with an adequate tool.

T cells: an emerging cast of roles in bipolar disorder

Bipolar disorder (BD) is a distinctly heterogeneous and multifactorial disorder with a high individual and social burden. Immune pathway dysregulation is an important pathophysiological feature of BD. Recent studies have suggested a potential role for T lymphocytes in the pathogenesis of BD. Therefore, greater insight into T lymphocytes' functioning in patients with BD is essential. In this narrative review, we describe the presence of an imbalance in the ratio and altered function of T lymphocyte subsets in BD patients, mainly in T helper (Th) 1, Th2, Th17 cells and regulatory T cells, and alterations in hormones, intracellular signaling, and microbiomes may be potential causes. Abnormal T cell presence explains the elevated rates of comorbid inflammatory illnesses in the BD population. We also update the findings on T cell-targeting drugs as potentially immunomodulatory therapeutic agents for BD disease in addition to classical mood stabilizers (lithium, valproic acid). In conclusion, an imbalance in T lymphocyte subpopulation ratios and altered function may be involved in the development of BD, and maintaining T cell immune homeostasis may provide an overall therapeutic benefit.

Childhood trauma relates to worse memory functioning in bipolar disorder

BACKGROUND

Childhood trauma is commonly experienced by individuals diagnosed with bipolar disorder (BP). In BP, childhood trauma is related to a more severe clinical course, but its association with cognition remains unclear.

METHODS

This study evaluated 405 adult participants diagnosed with BP and 136 controls. Participants completed the Childhood Trauma Questionnaire and a comprehensive neuropsychological battery. High versus low childhood trauma was defined with one standard deviation above the control participant's mean Childhood Trauma Questionnaire score. Neuropsychological data was transformed into eight cognitive factors, including four executive functioning, auditory and visual memory, fine motor, and emotion processing. Multivariate analysis of covariance evaluated group differences in cognition, while adjusting for covariates.

RESULTS

There were significant differences among the three groups, F(16, 968) = 4.05, p < .001, Wilks' Λ = 0.88, partial η² = 0.06. Comparing the high and low trauma BP groups, high trauma was related to lower auditory and visual memory factor scores (p < .05). As compared to controls, the BP high trauma group had lower scores on six of eight factors (all p < .01), while the BP low trauma group had lower scores on four of eight factors (all p < .01).

LIMITATIONS

Analyses of factor score do not address which aspect of the memory process is affected and biomarkers may help guide interventions addressing underlying biological process.

CONCLUSIONS

Adults diagnosed with BP with higher childhood trauma have worse memory functioning, beyond the lower childhood trauma BP group, highlighting the importance of understanding the long-term cognitive outcomes of childhood trauma.

An update on potential pharmacotherapies for cognitive impairment in bipolar disorder

INTRODUCTION

Cognitive impairment is a core feature of bipolar disorder (BD) that impedes recovery by preventing the return to optimal socio-occupational functioning and reducing quality of life. Presently, there are no efficacious treatments for cognitive impairment in BD, but many pharmacological interventions are being considered as they have the potential to target the underlying pathophysiology of the disorder.

AREAS COVERED

This review summarizes the available evidence for pharmacological interventions for cognitive impairment in bipolar disorder. We searched PubMed, MedLine, and PsycInfo from inception to December 1^st, 2022. Traditional treatments, such as lithium, anticonvulsants (lamotrigine), antipsychotics (aripiprazole, asenapine, cariprazine, lurasidone, and olanzapine), antidepressants (vortioxetine, fluoxetine, and tianeptine) and psychostimulants (modafinil), and emerging interventions, such as acetylcholinesterase inhibitors (galantamine and donepezil), dopamine agonists (pramipexole), erythropoietin, glucocorticoid receptor antagonists (mifepristone), immune modulators (infliximab, minocycline and doxycycline), ketamine, metabolic agents (insulin, metformin, and liraglutide), probiotic supplements, and Withania somnifera are discussed.

EXPERT OPINION

The investigation of interventions for cognitive impairment in BD is a relatively under-researched area. In the past, methodological pitfalls in BD cognition trials have also been a critical limiting factor. Expanding on the existing literature and identifying novel pharmacological and non-pharmacological treatments for cognitive impairment in BD should be a priority.

Modelling mood updating: a proof of principle study

BACKGROUND

Recent developments in computational psychiatry have led to the hypothesis that mood represents an expectation (prior belief) on the likely interoceptive consequences of action (i.e. emotion). This stems from ideas about how the brain navigates its external world by minimising an upper bound on surprisal (free energy) of sensory information and echoes developments in other perceptual domains.

AIMS

In this paper we aim to present a simple partial observable Markov decision process that models mood updating in response to stressful or non-stressful environmental fluctuations while seeking to minimise surprisal in relation to prior beliefs about the likely interoceptive signals experienced with specific actions (attenuating or amplifying stress and pleasure signals).

METHOD

We examine how, by altering these prior beliefs we can model mood updating in depression, mania and anxiety.

RESULTS

We discuss how these models provide a computational account of mood and its related psychopathology and relate it to previous research in reward processing.

CONCLUSIONS

Models such as this can provide hypotheses for experimental work and also open up the potential modelling of predicted disease trajectories in individual patients.

Cardiovascular risk in bipolar disorder - A case for the hypothalamus-pituitary-adrenal axis?

BACKGROUND

Unipolar major depressive disorder (MDD) and bipolar disorder (BD) are associated with elevated mortality risk secondary to natural causes. Cardiovascular disease (CVD) constitutes the most prevalent underlying condition. Patients with BD display higher CVD-associated excess mortality than MDD patients. Epicardial adipose tissue (EAT) volume, a known predictor of premature CV morbidity and adrenal gland (AG) volume, an indicator for chronic hypothalamus-pituitary-adrenal (HPA) axis activation, were compared in BD and MDD patients.

METHODS

Magnetic resonance imaging was performed to assess EAT and AG volume in age-, gender-, and body mass index (BMI)-matched MDD (N = 27) and BD (N = 27) patients. Ten-year CV mortality risk and diabetes risk were assessed by PROCAM, ESC-SCORE, and FINDRISK, respectively; metabolic syndrome (MetS) was determined following NCEP/ATP III criteria.

RESULTS

Cardiometabolic risk scores and frequency of MetS were comparable, and scores of cardiometabolic risk indices did not significantly differ in both groups. After adjustment for age, BMI, and physical activity, EAT and AG volumes were significantly higher in BD compared to MDD. Partial correlation analyses showed a significant positive association of EAT and AG volumes in BD but not in the MDD.

LIMITATIONS

The modest sample size warrants confirmation in a larger cohort and the cross-sectional design does not allow for temporal or causal inferences.

CONCLUSION

Our study indicates increased EAT accumulation in BD patients. This was associated with HPA axis dysregulation. Therapeutic lifestyle interventions that reduce EAT volume should be considered in clinical BD management.

Mammillary body and hypothalamic volumes in mood disorders

We have previously reported an in vivo enlargement of the left hypothalamus in mood disorders using 7 T magnetic resonance imaging. The aim of this follow-up study was to find out whether the hypothalamic volume difference may be located in the mammillary bodies (MB) rather than being widespread across the hypothalamus. We developed and evaluated a detailed segmentation algorithm that allowed a reliable segmentation of the MBs, and applied it to 20 unmedicated (MDDu) and 20 medicated patients with major depressive disorder, 21 medicated patients with bipolar disorder, and 23 controls. 20 out of 23 healthy controls were matched to the MDDu. We tested for group differences in MB and hypothalamus without MB (HTh) volumes using analyses of covariance. Associations between both volumes of interest were analysed using bivariate and partial correlations. In contrast to postmortem findings, we found no statistically significant differences of the MB volumes between the study groups. Left HTh volumes differed significantly across the study groups after correction for intracranial volume (ICV) and for ICV and sex. Our result of an HTh enlargement in mood disorders was confirmed by a paired t-test between the matched pairs of MDDu and healthy controls using the native MB and HTh volumes. In the whole sample, MB volumes correlated significantly with the ipsilateral HTh volumes. Our results indicate a structural relationship between both volumes, and that our previous in vivo finding of a hypothalamus enlargement does not extend to the MB, but is limited to the HTh. The enlargement is more likely related to the dysregulation of the HPA axis than to cognitive dysfunctions accompanying mood disorders.

Targeting the Arginine Vasopressin V1b Receptor System and Stress Response in Depression and Other Neuropsychiatric Disorders

A healthy stress response is critical for good mental and overall health and promotes neuronal growth and adaptation, but the intricately balanced biological mechanisms that facilitate a stress response can also result in predisposition to disease when that equilibrium is disrupted. The hypothalamic-pituitary-adrenal (HPA) axis neuroendocrine system plays a critical role in the body's response and adaptation to stress, and vasopressinergic regulation of the HPA axis is critical to maintaining system responsiveness during chronic stress. However, exposure to repeated or excessive physical or emotional stress or trauma can shift the body's stress response equilibrium to a "new normal" underpinned by enduring changes in HPA axis function. Exposure to early life stress due to adverse childhood experiences can also lead to lasting neurobiological changes, including in HPA axis function. HPA axis impairment in patients with depression is considered among the most reliable findings in biological psychiatry, and chronic stress has been shown to play a major role in the pathogenesis and onset of depression and other neuropsychiatric disorders. Modulating HPA axis activity, for example via targeted antagonism of the vasopressin V_1b receptor, is a promising approach for patients with depression and other neuropsychiatric disorders associated with HPA axis impairment. Despite favorable preclinical indications in animal models, demonstration of clinical efficacy for the treatment of depressive disorders by targeting HPA axis dysfunction has been challenging, possibly due to the heterogeneity and syndromal nature of depressive disorders. Measures of HPA axis function, such as elevated cortisol levels, may be useful biomarkers for identifying patients who may benefit from treatments that modulate HPA axis activity. Utilizing clinical biomarkers to identify subsets of patients with impaired HPA axis function who may benefit is a promising next step in fine-tuning HPA axis activity via targeted antagonism of the V_1b receptor.

Is Bipolar Disorder the Consequence of a Genetic Weakness or Not Having Correctly Used a Potential Adaptive Condition?

It is hypothesized that factors associated with bipolar disorder could, uer defined conditions, produce adaptive behaviors. The aim is to verify whether a genetic feature associated with bipolar disorder can be found in people without bipolar disorder but with hyperactivity/exploration traits. Healthy old adults (N = 40) recruited for a previous study on exercise were subdivided using a previously validated tool into those with and without hyperactivity/exploration traits and compared with a group of old patients with bipolar disorder (N = 21). The genetic variant RS1006737 of CACNA1C was analyzed using blood samples, DNA extraction, real-time PCR, FRET probes, and SANGER method sequencing. People with hyperactivity/exploration traits and without bipolar disorder were like people with bipolar disorder regarding the frequency of the genetic variant (OR = 0.79, CI95%: 0.21-2.95), but were different from people without either hyperactivity/exploration traits and bipolar disorder (OR = 4.75, CI95%: 1.19-18.91). The combined group of people with hyperactivity/exploration traits without bipolar disorder plus people with bipolar disorder had a higher frequency of the variant than people without either hyperactivity/exploration traits or bipolar disorder (OR = 4.25, CI95%: 1.24-14.4). To consider the genetic profile of bipolar disorder not an aberrant condition opens the way to a new approach in which the adaptive potential would be a central point in psychosocial treatment in addition to drug therapy. Future research can confirm the results of our study.

Persisting neuropsychiatric symptoms, Alzheimer's disease, and cerebrospinal fluid cortisol and dehydroepiandrosterone sulfate

INTRODUCTION

Neuropsychiatric symptoms are important treatment targets in the management of dementia and can be present at very early clinical stages of neurodegenerative diseases. Increased cortisol has been reported in Alzheimer's disease (AD) and has been associated with faster cognitive decline. Elevated cortisol output has been observed in relation to perceived stress, depression, and anxiety. Dehydroepiandrosterone sulfate (DHEAS) has known anti-glucocorticoid effects and may counter the effects of cortisol.

OBJECTIVES

We aimed to examine whether CSF cortisol and DHEAS levels were associated with (1) neuropsychiatric symptoms at baseline, (2) changes in neuropsychiatric symptoms over 3 years, and (3) whether these associations were related to or independent of AD pathology.

METHODS

One hundred and eighteen participants on a prospective study in a memory clinic setting, including patients with cognitive impairment (n = 78), i.e., mild cognitive impairment or mild dementia, and volunteers with normal cognition (n = 40), were included. Neuropsychiatric symptoms were assessed using the Neuropsychiatric Inventory Questionnaire (NPI-Q). CSF cortisol and DHEAS, as well as CSF AD biomarkers, were obtained at baseline. Neuropsychiatric symptoms were re-assessed at follow-up visits 18 and 36 months from baseline. We constructed linear regression models to examine the links between baseline neuropsychiatric symptoms, the presence of AD pathology as indicated by CSF biomarkers, and CSF cortisol and DHEAS. We used repeated-measures mixed ANCOVA models to examine the associations between the neuropsychiatric symptoms' changes over time, baseline CSF cortisol and DHEAS, and AD pathology.

RESULTS

Higher CSF cortisol was associated with higher NPI-Q severity scores at baseline after controlling for covariates including AD pathology status (B = 0.085 [0.027; 0.144], p = 0.027; r = 0.277). In particular, higher CSF cortisol was associated with higher baseline scores of depression/dysphoria, anxiety, and apathy/indifference. Elevated CSF cortisol was also associated with more marked increase in NPI-Q scores over time regardless of AD status (p = 0.036, η² = 0.207), but this association was no longer significant after controlling for BMI and the use of psychotropic medications. CSF DHEAS was associated neither with NPI-Q scores at baseline nor with their change over time. Cortisol did not mediate the association between baseline NPI-Q and changes in clinical dementia rating sum of boxes over 36 months.

CONCLUSION

Higher CSF cortisol may reflect or contribute to more severe neuropsychiatric symptoms at baseline, as well as more pronounced worsening over 3 years, independently of the presence of AD pathology. Our findings also suggest that interventions targeting the HPA axis may be helpful to treat neuropsychiatric symptoms in patients with dementia.

Mania associated olfactory dysfunction: A comparison between bipolar subjects in mania and remission

OBJECTIVES

The aim of this study was to assess the olfactory functions of patients with bipolar disorder in manic phase and to compare them to those of bipolar subjects in remission and healthy controls.

METHODS

We recruited 96 participants divided in 3 groups: bipolar mania (MB), euthymic bipolar in remission (EB) and healthy controls (HC). All participants underwent an assessment of their olfactory functions using the Sniffin' sticks threshold and identification tests. Odors' pleasantness, intensity, familiarity and emotion were assessed. All participants were screened for the presence of psychiatric disorder through the MINI questionnaire. Clinical evaluation explored dimensions of mania, depression, anxiety respectively through YMRS, MADRS and STAI scales. Anhedonia was explored through the Chapman physical and social anhedonia questionnaire.

RESULTS

Patients in mania had deficits in identifying positive smells compared to bipolar subjects in remission and to healthy controls (MB < EB < HC; p < 0.001). Hedonic (MB < EB = HC; p < 0.001) and emotional (MB < EB = HC; p < 0.001) ratings of positive smells were lower in patients in manic phase compared to remitted subjects or controls. Mania was associated to higher emotion rating of negative smells compared to remitted subjects and controls (MB > EB = HC; p < 0.001). There was no difference between the 3 groups in the ratings of intensity and familiarity of smells, as well as in the olfactory threshold testing. The 3 groups showed no difference in the identification of negative smells.

CONCLUSIONS

Patients in manic episodes showed deficits in identifying positive odors. They evaluated these smells as less pleasant and less emotional compared to remitted bipolar subjects and healthy controls. These olfactory dysfunctions may constitute potential indicators of manic state. The persistence of olfactory dysfunction in remission phase (deficit in the olfactory identification of positive odors compared to healthy controls) may constitute a potential trait indicator of bipolarity.

Expression of type 1 cannabinoid receptor gene in bipolar disorder

BACKGROUND

The Endocannabinoid System (ECBs) may have a crucial role in bipolar disorder (BD). Previous reports have not detected abnormalities in the expression of the cannabinoid receptor gene CNR1, encoding for CB₁. However, we hypothesized that differentiating between mania and depression may uncover differences in CNR1 expression levels.

METHODS

We recruited 44 subjects with BD type I (BD-I), in mania (n = 22) and depression (n = 22) and 25 Healthy Controls (HC). CNR1 gene expression was analyzed using a quantitative real-time polymerase chain reaction from peripheral blood mononuclear cells. Data were analyzed using frequentist non-parametric and Bayesian approaches (generalized location-scale model based on lognormal and gamma distributions).

RESULTS

Using the frequentist non-parametric approach, the depression group had lower CNR1 expression compared to the mania group (p = 0.004). In addition, there was a negative correlation between CNR1 expression and Hamilton Depression Scale score (rho = -0.37; p = 0.007). Bayesian analyses further revealed that CNR1 expression in the mania group was higher and less variable than among HC (>95% probability), while CNR1 expression in the depression group was lower and more variable than among HC (100% probability).

LIMITATIONS

Lack of participants with bipolar disorder in the euthymic phase, lack of toxicology screening and evaluation of CNR1 variants.

CONCLUSION

CNR1 expression is higher and less variable in mania than in depression. It is highly probable that these differences also distinguish individuals in different illness phases from healthy controls. Future studies are needed to clarify the role of the endocannabinoid system in bipolar disorder.