Fifty years on: Serotonin and depression

The neural basis of affective empathy: What is known from rodents

Empathy is the cornerstone of social interactions between conspecies for human beings and other social animals. Human beings with empathy defects might either suffer unpleasant or failed social interactions as ASD patients, or even display antisocial behaviors. To find efficient cure for empathy defects, first of all, the neural mechanisms underpinning various empathy behaviors should be well studied and understood. And the research in the field of affective empathy thrives fast in recent years. It is necessary to review the important contributions in this field, especially for understanding the delicate neural mechanisms of diverse forms of affective empathy. Here, we have summarized the characteristics of various types of affective empathy. We also discuss the distinctions between empathy for pain and fear, as well as instinctive and experienced empathy. Our analysis further highlights the findings in the complex neural mechanisms and potential brain regions underlying different affective empathy behaviors. Above all, this work is expected to help enhance our comprehension of behavioral dynamics and neural basis of affective empathy along with its role in emotional regulation and social behavior.

Study on the comorbid mechanisms of sarcopenia and late-life depression

The increasing global aging population has brought greater focus to age-related diseases, particularly muscle-brain comorbidities such as sarcopenia and late-life depression. Sarcopenia, defined by the gradual loss of muscle mass and function, is notably prevalent among older individuals, while late-life depression profoundly affects their mental health and overall well-being. Epidemiological evidence suggests a high co-occurrence of these two conditions, although the precise biological mechanisms linking them remain inadequately understood. This review synthesizes the existing body of literature on sarcopenia and late-life depression, examining their definitions, prevalence, clinical presentations, and available treatments. The goal is to clarify the potential connections between these comorbidities and offer a theoretical framework for the development of future preventive and therapeutic strategies.

Association Among Depressive Symptoms, Physical Symptoms, Serotonin Levels, and Gambling Disorder: A Case-Control Study

PURPOSE

The current study compares depressive symptoms, physical symptoms, and serotonin levels between individuals with gambling disorder (GD) and healthy controls (HC), investigates their relationship, and identifies factors that predict the development of GD.

METHOD

A case-control study with purposive convenience sampling was conducted using data from GD (n = 76) and HC (n = 56) groups.

RESULTS

Increased depressive symptoms were associated with greater physical symptoms (r = 0.70, p < 0.001) and problem gambling severity (r = 0.37, p = 0.001). Decreased serotonin levels suggest a potential depressive disorder; however, not all individuals had lower serotonin levels, indicating emotionally vulnerable subgroups. Increased serotonin levels correlated with restlessness, which was associated with problem gambling (r = 0.31, p = 0.006). Decreased problem gambling severity was linked to increased alcohol use (r = -0.29, p = 0.012).

CONCLUSION

Results indicate a correlation among depressive symptoms, physical symptoms, and serotonin imbalance in individuals with GD. [Journal of Psychosocial Nursing and Mental Health Services, xx(x), xx-xx.].

Drosophila model of depression-like behavior: systematic investigation of external stress parameters and intrinsic susceptibility

Currently, Drosophila is widely used to study brain diseases. Unfortunately, Drosophila still lacks a mature and stable model for research on depression. This study addressed this issue by systematically exploring external stress and intrinsic susceptibility factors (Drosophila strains, adult/larval forms) that may influence the establishment and reproducibility of the stress-induced model. On this basis, the parameters are optimized. The results indicate Drosophila strains and forms are critical factors influencing model establishment, while external stress is the primary cause affecting the model's mortality rate. Compared with the other four strains, Canton-S are the most susceptible to chronic unpredictable mild stress (CUMS). Larval forms exhibit lower reactivity to external stress compared to adults. Parameter variations greatly influence model mortality rates from cold/heat/starvation stress. The model methodology validation study conducted subsequently through assessments of face, construct, and predictive validity demonstrates that the model exhibits face (neurobehavioral differences), structural (neurotransmitter changes in the Drosophila brain), and predictive (behavioral changes after fluoxetine treatment) validity. Additionally, spatial behavior experiments in Drosophila provide more realistic activity patterns compared to planar behavior, minimizing potential errors in interpreting lateral movements of the Drosophila, and it is recommended that this metric be included in model evaluation. This study presents a comprehensive set of methods for establishing and evaluating a depression-like behavior model and offers greater convenience for research on the pathogenesis of depression, as well as the screening, efficacy evaluation, and mechanistic studies of antidepressant drugs.

From Stress to Synapse: The Neuronal Atrophy Pathway to Mood Dysregulation

Mood disorders, including major depressive disorder and bipolar disorder, are among the most prevalent mental health conditions globally, yet their underlying mechanisms remain incompletely understood. This review critically examines the neuronal atrophy hypothesis, which posits that chronic stress and associated neurobiological changes lead to structural and functional deficits in critical brain regions, contributing to mood disorder pathogenesis. Key mechanisms explored include dysregulation of neurotrophic factors such as brain-derived neurotrophic factor (BDNF), elevated glucocorticoids from stress responses, neuroinflammation mediated by cytokines, and mitochondrial dysfunction disrupting neuronal energy metabolism. These processes collectively impair synaptic plasticity, exacerbate structural atrophy, and perpetuate mood dysregulation. Emerging evidence from neuroimaging, genetic, and epigenetic studies underscores the complexity of these interactions and highlights the role of environmental factors such as early-life stress and urbanization. Furthermore, therapeutic strategies targeting neuroplasticity, including novel pharmacological agents, lifestyle interventions, and anti-inflammatory treatments, are discussed as promising avenues for improving patient outcomes. Advancing our understanding of the neuronal atrophy hypothesis could lead to more effective, sustainable interventions for managing mood disorders and mitigating their global health burden.

Estrogen-Gut-Brain Axis: Examining the Role of Combined Oral Contraceptives on Mental Health Through Their Impact on the Gut Microbiome

Combined oral contraceptives (COCs) possess the ability to alter the normal composition of the gut microbiome and the permeability of the gastrointestinal (GI) tract, which may cause both gut-related and non-gut-related complications. The gut-estrogen axis examines the relationship between estrogens (particularly the active form, estradiol) and the gastrointestinal system and can be attributed to the maintenance of the estrobolome and circulating estradiol levels. The gut-brain axis involves the relationship between the brain and the gastrointestinal system and can be attributed to the gut microbiome in relation to the enteric nervous system (ENS) and serotonin levels. Overall, the introduction of exogenous hormones into an endogenous environment alters the normal balance of both hormones and bacteria. Currently, there is a gap in knowledge regarding the link between COCs and mental health complications such as anxiety and depression, and the diversity in these complications may be related to different types of COCs, their composition, and variations in study populations. This article reviews existing evidence from animal and human studies on the role of COCs in the development of mental health issues through their impact on the gut microbiome.

miRNAs in Major Depression: Possible Association of miR-17 and miR-92 with Childhood Traumas

Objective

Psychosocial and genetic factors are considered to play roles in the etiological mechanisms of major depressive disorder (MDD). The involvement of miRNAs in the etiopathogenesis of depression and childhood traumas is still unclear. This study aims to reveal potential differences in miRNA levels between patients with depression and healthy individuals and assess their connection to childhood traumas.

Methods

This study included fifty patients with MDD and 33 healthy controls. The targeting of the 3'UTR regions of the BDNF, SLC6A4/SERT/5-HTT, HTR1a, and HTR2a genes by 8 miRNAs was analyzed to explore their potential involvement in depression and childhood traumas. The Hamilton Depression Rating Scale, the Hamilton Anxiety Rating Scale, and the Childhood Trauma Questionnaire-28 were administered to the participants.

Results

Patients with MDD exhibited significantly lower expression levels of miR-335 and miR-4775, as well as significantly higher expression levels of miR-15, miR-16, miR-17, miR-92, miR-182, and miR-206, when compared to healthy controls using the 2-(ΔΔCt) method. Only miR-17 and miR-92 were associated with childhood traumas in the patients with depression.

Conclusion

Our research reveals a possible involvement of miRNAs in the pathophysiology of depression and highlights a potential relationship between childhood traumas and specific miRNAs in depressed patients.

Efficacy of Transcranial Direct Current Stimulation (tDCS) on Neuropsychiatric Symptoms in Substance Use Disorder (SUD)-A Review and Insights into Possible Mechanisms of Action

Introduction: Substance use disorder (SUD) is a significant global clinical issue marked by the excessive consumption of alcohol, nicotine, and various psychoactive substances, leading to impaired social, cognitive, and occupational functioning. Individuals with SUD frequently experience depression and anxiety disorders, which exacerbate their prognosis and contribute to substantial health and social burdens. The pathophysiology of SUD and its associated conditions is multifaceted, involving multiple dysfunctions in the brain. This complexity underscores an urgent need for the development of noninvasive treatments that can directly target the brain. One of them is transcranial direct current stimulation (tDCS), an intensively studied technique for safely modulating cortical excitability. The aim of this study is to investigate the effectiveness of tDCS in treating symptoms of depression and anxiety in SUD. Methods: With an emphasis on the underlying mechanisms of action, this mechanistic review investigates the effectiveness of tDCS in treating anxiety and depression in SUD patients. Literature searches were conducted using the PubMed/Medline, ResearchGate, Cochrane, and Google Scholar databases. Results: The review identified 12 relevant studies. The results showed that left dorsolateral prefrontal cortex (DLPFC) stimulation is an effective treatment option for depression in SUD. In anxiety disorders, left and right DLPFC stimulation is effective, with better results observed with right DLPFC stimulation. However, the included studies differed in their methodology, sample characteristics, and measurement methods, which could have influenced the final results of the analysis. The central focus of this mechanistic review is to discuss the potential mechanisms of action of tDCS in treating depression and anxiety in SUD. These mechanisms include the modulation of brain networks, a reduction in neuroinflammation, an enhancement in neuroplasticity, and an increase in P300 amplitude. We also discuss the limitations of the included studies and propose ways to address them in future research. Conclusions: This review provides evidence that tDCS is an effective treatment option for anxiety and depression in SUD. Stimulation of the left DLPFC reduces symptoms of depression, while stimulation of the right DLPFC reduces symptoms of anxiety. However, future research is required to confirm these findings and to deepen our understanding of the mechanisms through which tDCS exerts its effects in this context. Neuroimaging methods (fMRI and EEG) and blood tests could be particularly useful.

Characterizing metabolomic and proteomic changes in depression: a systematic analysis

Despite the widespread use of metabolomics and proteomics to explore the molecular landscape of depression, there is a lack of consensus regarding dysregulated molecules with replicable evidence. Thus, this study aimed to identify robust metabolomic and proteomic features in depression by integrating evidence from large-scale studies. In this study, a knowledge base-mining approach was adopted to compile a list of dysregulated molecules derived from metabolomic and proteomic studies. A vote-counting approach was performed to identify consistently altered molecules in the blood and urine samples of patients with depression. A total of 2398 molecular entries were selected, comprising 857 unique metabolites and 468 unique proteins from 143 metabolomic and 23 proteomic studies in depression. The results of vote-counting analyses revealed that 11 metabolites in blood and 5 metabolites in urine exhibited consistent disturbances across studies. Circulating levels of glutamic acid and phosphatidylcholine (32:0) were elevated in depressive patients, whereas the levels of tryptophan, kynurenic acid, kynurenine, acetylcarnitine, serotonin, creatinine, inosine, phenylalanine, and valine were lower. Urinary levels of isobutyric acid, alanine, and nicotinic acid were higher, whereas the levels of N-methylnicotinamide and tyrosine were lower. Moreover, analysis of the proteomic dataset identified only one circulating protein, ceruloplasmin, that was consistently dysregulated. Convergence comparison prioritized tryptophan as the top-ranked circulating metabolite, followed by kynurenic acid, acetylcarnitine, creatinine, serotonin, and valine. Collectively, robust evidence of metabolomic changes was observed in patients with depression, pointing to a role as potential biomarkers. Further investigation of consensus proteomic features for depression is necessitated.

A novel hypothesis-generating computational workflow utilizing reverse pharmacophore mapping-A drug repurposing perspective of istradefylline towards major depressive disorder

BACKGROUND AND PURPOSE

Drug repurposing (DR) offers a compelling alternative to traditional drug discovery's lengthy, resource-intensive process. DR is the process of identifying alternative clinical applications for pre-approved drugs as a low-risk and low-cost strategy. Computational approaches are crucial during the early hypothesis-generating stage of DR. However, 'large-scale' data retrieval remains a significant challenge. A computational workflow addressing such limitations might improve hypothesis generation, ultimately benefit patients and advance DR research.

EXPERIMENTAL APPROACH

We introduce a novel computational workflow (combining free-accessible computational platforms) to provide 'proof-of-concept' of the pre-approved drug's suitability for repurposing. Three key phases are included: target fishing (via reverse pharmacophore mapping), target identification (via disease- and drug-target pathway identification) and retrospective literature and drug-like analysis (via in silico ADMET properties determination). Istradefylline is a Parkinson's disease-approved drug with literature-attributed antidepressant properties remaining unclear. Practically applied, istradefylline's antidepressant activity was assessed in the context of major depressive disorder (MDD).

KEY RESULTS

Data mining aided by target identification resulted in istradefylline potentially representing a novel antidepressant drug class. Retrieved drug targets (KYNU, MAO-B, ALOX12 and PLCB2) associated with selected MDD pathways (tryptophan metabolism and serotonergic synapse) generated a hypothesis that istradefylline increased extracellular 5-HT levels (MAO-B inhibition) and reduced inflammation (KYNU, ALOX12 and PLCB2 inhibition).

CONCLUSION AND IMPLICATIONS

The practically applied workflow's generated hypothesis aligns with known experimental data, validating the effectiveness of this novel computational workflow. It is a low-risk and low-cost DR computational tool providing a bird's-eye view for exploring alternative clinical applications of pre-approved drugs.

Physical Activity and Depression in Breast Cancer Patients: Mechanisms and Therapeutic Potential

Breast cancer is a significant traumatic experience that often leads to chronic stress and mental health challenges. Research has consistently shown that physical activity-especially exercise-can alleviate depressive symptoms; however, the specific biological mechanisms underlying these antidepressant effects remain unclear. In this review, we comprehensively summarize the biological mechanisms of depression and the antidepressant mechanisms of physical activity and explore the biological processes through which exercise exerts its antidepressant effects in breast cancer patients. We focus on the impact of physical activity on inflammation, the endocrine system, glutamate, and other aspects, all of which play crucial roles in the pathophysiology of depression. Moreover, we discuss the heterogeneity of depression in breast cancer patients and the complex interactions between its underlying mechanisms. Additionally, we propose that a deeper understanding of these mechanisms in the breast cancer population can guide the design and implementation of exercise-based interventions that maximize the antidepressant benefits of physical activity. Finally, we summarize the current research and propose future research directions.

Estradiol metabolism by gut microbiota in women's depression pathogenesis: inspiration from nature

The recurrence and treatment resistance of depression remain significant issues, primarily due to an inadequate understanding of its pathogenesis. Recent scientific evidence indicates that gut microbiota influence estradiol metabolism and are associated with the development of depression in nonpremenopausal women. Integrating existing studies on the regulation of estradiol metabolism by microorganisms in nature and the relevance of its degradation products to depression, recent scientific explorations have further elucidated the key mechanisms by which gut microbiota catabolize estradiol through specific metabolic pathways. These emerging scientific findings suggest that the unique metabolic effects of gut microbiota on estradiol may be one of the central drivers in the onset and course of depression in non-menopausal women.

Horticultural activity in soil inoculated with Streptomyces rimosus improved depressive mood with altered electroencephalogram and serum metabolism in adults

This study investigated the psychophysiological and metabolomic changes during horticultural activities involving the inhalation of volatile organic compounds (VOCs) in individuals experiencing depressive mood based on the presence or absence of the soil microbe Streptomyces rimosus, which emits VOCs. Thirty participants met the specific depression and anxiety criteria and engaged in horticultural activities using soil inoculated with S. rimosus (experimental group) or medium (control group). Electroencephalogram (EEG) was used to analyze the resulting psychophysiological response, and blood samples were collected after each activity. Significant increases were observed in the FZ channel of the central frontal lobe for relative theta, relative alpha, relative slow alpha, ratio of sensorimotor rhythm mid beta to theta, and ratio of alpha to high beta, whereas significant decreases were noted for relative beta, relative high beta, and relative gamma and spectral edge frequency 50% and 90%. GC-TOF-MS analysis identified 44 altered serum metabolites, showing an increasing trend in succinate, glycolate, glycerate, acetate, palmitate, myristate, laurate, caprynate, and octanoate, which are related to the citrate cycle, glyoxylate and dicarboxylate metabolism, and fatty acid biosynthesis. In conclusion, this study suggests that inhalation of VOCs during horticultural activities can help alleviate depression and depressive moods.

Navigating the depths: A comprehensive narrative review on depression in people with epilepsy

Epilepsy presents a significant global health challenge, impacting millions worldwide. Alarmingly, over half of individuals living with epilepsy (PWE) also face concurrent medical conditions, with psychiatric complications, particularly depression, standing out as prevalent issues. The relationship between epilepsy and depression is complex and bidirectional, with approximately a quarter of adults with epilepsy receiving a diagnosis of depression. This complexity underscores the challenges in diagnosing depression in epilepsy patients, hindered by overlapping symptoms and distinct manifestations of depression in this population. Our review highlights that the use of most antidepressant pharmacotherapies does not increase the risk of seizure occurrences. On the contrary, compelling evidence suggests that such treatments may even decrease seizure frequency, offering hope for patients. In addition to pharmacology, non-pharmacological interventions are emerging as vital alternatives, enriching the therapeutic landscape. However, despite these promising avenues, a significant gap in our understanding persists, characterized by a lack of comprehensive, prospective research. Our review rigorously explores the latest pathophysiological insights linking depression and epilepsy while critically evaluating contemporary treatment paradigms for individuals grappling with these comorbid conditions. By focusing on the most current developments, this review aims to equip clinicians with cutting-edge knowledge, fostering a more nuanced and effective approach to managing the intricate interplay between epilepsy and comorbid depression.

Pharmaceutical Studies on Piperazine-based Compounds Targeting Serotonin Receptors and Serotonin Reuptake Transporters

Depression is a debilitating mental illness that has a significant impact on an individual's psychological, social, and physical life. Multiple factors, such as genetic factors and abnormalities in neurotransmitter levels, contribute to the development of depression. Monoamine oxidase inhibitors, tricyclic antidepressants, selective serotonin reuptake inhibitors (SSRIs), serotoninnoradrenaline reuptake inhibitors, and atypical and new-generation antidepressants are well-known drug classes. SSRIs are the commonly prescribed antidepressant medications in the clinic. Genetic variations impacting serotonergic activity in people can influence susceptibility to diseases and response to antidepressant therapy. Gene polymorphisms related to 5-hydroxytryptamine (5-HT) signaling and subtypes of 5-HT receptors may play a role in the development of depression and the response to antidepressants. SSRIs binding to 5-HT reuptake transporters help relieve depression symptoms. Research has been conducted to identify a biomarker for detecting depressive disorders to identify new treatment targets and maybe offer novel therapy approaches. The pharmacological potentials of the piperazine-based compounds led researchers to design new piperazine derivatives and to examine their pharmacological activities. Structure-activity relationships indicated that the first aspect is the flexibility in the molecules, where a linker of typically a 2-4 carbon chain joins two aromatic sides, one of which is attached to a piperazine/phenylpiperazine/benzyl piperazine moiety. Newly investigated compounds having a piperazine core show a superior antidepressant effect compared to SSRIs in vitro/in vivo.

Neuropsychiatric symptoms as early indicators of brain tumors

Brain tumors, despite the high mortality and morbidity, they are a rare type of heterogenous tumors that are highly dependent on sex, age, race, level of education, and socioeconomic status. Due to their high mortality rates, it is important to identify as many potential biomarkers for early detection as the earlier the tumor is discovered, the better the prognosis. One such early biomarker we propose in the current paper is the assessment of anxiety, depression, and cognitive changes. In most cancer patients, a certain degree of anxiety and depression is expected upon receiving the diagnosis as it triggers fears regarding the prognosis, possible side effects of the treatment, and even the possibility of the treatment failing. In this paper we analyzed the way anxiety, depression, and cognitive changes present themselves in the case of several types of tumors and whether these could be used as early markers. We have observed that most of the cognitive changes present are due to the location, size, and type of the tumor with some highly connected to anxiety and depression. Moreover, in the case of certain tumors, the removal of the mass has not improved the mood or cognitive function.

S-(+)-mecamylamine increases the firing rate of serotonin neurons and diminishes depressive-like behaviors in an animal model of stress

Mecamylamine, a noncompetitive blocker of nicotinic acetylcholine receptors (nAChRs), is the racemic mixture of two stereoisomers: S-(+)-mecamylamine (S-mec) and R-(-)-mecamylamine (R-mec), with distinct interactions with α4β2 nAChRs. It has been shown that mecamylamine increases glutamate release and excites serotonergic (5-HT) neurons in the dorsal raphe nucleus (DRN). In this study, we separately evaluated the effects of S-mec and R-mec on 5-HT neuron excitability. S-mec (3 μM) increased firing frequency by 40 %, while R-mec (3 μM) raised it by only 22 %. S-mec acts as a positive allosteric modulator on high-sensitivity (HS) α4β2 nAChRs at glutamate terminals, enhancing spontaneous excitatory postsynaptic currents (sEPSCs) in 5-HT neurons. Conversely, R-mec decreased sEPSCs by blocking HS α4β2 nAChRs and reduced GABA-mediated inhibitory currents (sIPSCs) by blocking α7 nAChRs at GABAergic terminals. These mechanisms make S-mec more effective than R-mec in enhancing 5-HT neuron firing. Moreover, combining S-mec with TC-2559, a selective agonist of HS α4β2 nAChRs, increased firing frequency by 65 %, exceeding the effect of S-mec alone. To validate these findings, we evaluated the antidepressant effects of S-mec (1 mg/kg) combined with TC-2559 or RJR-2403, another α4β2 nAChR agonist. This combination successfully reduced depression-like behaviors, suggesting a potential treatment strategy for patients resistant to conventional antidepressants.

Beyond the serotonin deficit hypothesis: communicating a neuroplasticity framework of major depressive disorder

The serotonin deficit hypothesis explanation for major depressive disorder (MDD) has persisted among clinicians and the general public alike despite insufficient supporting evidence. To combat rising mental health crises and eroding public trust in science and medicine, researchers and clinicians must be able to communicate to patients and the public an updated framework of MDD: one that is (1) accessible to a general audience, (2) accurately integrates current evidence about the efficacy of conventional serotonergic antidepressants with broader and deeper understandings of pathophysiology and treatment, and (3) capable of accommodating new evidence. In this article, we summarize a framework for the pathophysiology and treatment of MDD that is informed by clinical and preclinical research in psychiatry and neuroscience. First, we discuss how MDD can be understood as inflexibility in cognitive and emotional brain circuits that involves a persistent negativity bias. Second, we discuss how effective treatments for MDD enhance mechanisms of neuroplasticity-including via serotonergic interventions-to restore synaptic, network, and behavioral function in ways that facilitate adaptive cognitive and emotional processing. These treatments include typical monoaminergic antidepressants, novel antidepressants like ketamine and psychedelics, and psychotherapy and neuromodulation techniques. At the end of the article, we discuss this framework from the perspective of effective science communication and provide useful language and metaphors for researchers, clinicians, and other professionals discussing MDD with a general or patient audience.

Adverse psychiatric effects of psychedelic drugs: a systematic review of case reports

BACKGROUND

Psychedelic drugs are a focus of interest in the treatment of depression and other disorders but there are longstanding concerns about possible adverse psychiatric consequences. Because the relevant literature is largely informal, the seriousness of these risks is difficult to evaluate.

METHODS

Searches were made for case reports of schizophrenia-spectrum, affective or other psychiatric disorders after use of psychedelic drugs. Case reports of flashbacks were also searched for. Individuals with recent use of other drugs (apart from cannabis and alcohol) and/or a previous history of major psychiatric disorder were excluded. Symptoms were tabulated using the Syndrome Check List of the Present State Examination (PSE-9).

RESULTS

We found 17 case reports of schizophrenia spectrum disorder, 17 of affective disorder (depression, mania, or both), 3 cases of anxiety, 1 of depersonalization, and 1 of unclassifiable illness. The states could develop after a single use of the drug (5/17 schizophrenia; 6/17 affective disorder), and duration was highly variable. Recovery was the rule in cases of affective disorder but not in schizophrenia spectrum disorder. Twelve of 29 cases of flashbacks showed psychiatric symptomatology definitely outlasting the attacks, mainly anxiety (5 cases) and depression (8 cases). Flashback symptoms resolved within twelve months in approximately half of the cases but in a few persisted for years.

CONCLUSIONS

Reliable descriptions of schizophrenia spectrum disorder and major affective disorder after psychedelic drug use disorder exist but are relatively uncommon. Flashbacks are sometimes but not always associated with psychiatric symptomatology, mainly anxiety or depression.

Accurately predicting mood episodes in mood disorder patients using wearable sleep and circadian rhythm features

Wearable devices enable passive collection of sleep, heart rate, and step-count data, offering potential for mood episode prediction in mood disorder patients. However, current models often require various data types, limiting real-world application. Here, we develop models that predict future episodes using only sleep-wake data, easily gathered through smartphones and wearables when trained on an individual's sleep-wake history and past mood episodes. Using mathematical modeling to longitudinal data from 168 patients (587 days average clinical follow-up, 267 days wearable data), we derived 36 sleep and circadian rhythm features. These features enabled accurate next-day predictions for depressive, manic, and hypomanic episodes (AUCs: 0.80, 0.98, 0.95). Notably, daily circadian phase shifts were the most significant predictors: delays linked to depressive episodes, advances to manic episodes. This prospective observational cohort study (ClinicalTrials.gov: NCT03088657, 2017-3-23) shows sleep-wake data, combined with prior mood episode history, can effectively predict mood episodes, enhancing mood disorder management.

Rethinking the role of TRKB in the action of antidepressants and psychedelics

Antidepressant drugs promote neuronal plasticity, and activation of brain-derived neurotrophic factor (BDNF) signaling through its receptor neuronal receptor tyrosine kinase 2 (NTRK2 or TRKB) is among the critical steps in this process. These mechanisms are shared by typical slow-acting antidepressants, fast-acting ketamine, and psychedelic compounds, although the cellular targets of each drug differ. In this opinion article, we propose that some of these antidepressants may directly bind to TRKB and allosterically potentiate BDNF signaling, among other possible effects. TRKB activation in parvalbumin-containing interneurons disinhibits cortical networks and reactivates a juvenile-like plasticity window. Subsequent rewiring of aberrant networks, coupled with environmental stimuli, may underlie its clinical antidepressant effects. The end-to-end hypothesis proposed may stimulate the search for new treatment strategies.

Investigation of the Relationship between Plasma Nesfatin-1 Levels and Neutering in Dogs

Neutering of dogs, whether male or female, provides various benefits such as contraception, population control, and the prevention of reproductive disorders and undesirable sexual behaviors. However, it is also associated with an increased risk of obesity, which may be directly linked to post-neutering hormonal changes. Our study aims to determine the effects of neutering on plasma levels of nesfatin-1, serotonin, dopamine, TSH, and T4-hormones implicated in obesity and metabolic regulation. Fourteen dogs (seven males and seven females), aged between 1 and 3 years, were included in this study. Male dogs underwent orchiectomy and females underwent ovariohysterectomy. Blood samples were collected before surgery and on days 7 and 14 post-operatively to measure the plasma levels of these hormones using ELISA. The results showed a significant decrease in nesfatin-1, serotonin, and T4 levels, along with a significant increase in TSH levels in both male and female dogs post-neutering. While these hormonal changes are likely part of the body's adaptive response to neutering, they may represent a potential mechanism that contributes to the long-term tendency toward obesity in neutered dogs.

Serotonin effects on human iPSC-derived neural cell functions: from mitochondria to depression

Depression's link to serotonin dysregulation is well-known. The monoamine theory posits that depression results from impaired serotonin activity, leading to the development of antidepressants targeting serotonin levels. However, their limited efficacy suggests a more complex cause. Recent studies highlight mitochondria as key players in depression's pathophysiology. Mounting evidence indicates that mitochondrial dysfunction significantly correlates with major depressive disorder (MDD), underscoring its pivotal role in depression. Exploring the serotonin-mitochondrial connection, our study investigated the effects of chronic serotonin treatment on induced-pluripotent stem cell-derived astrocytes and neurons from healthy controls and two case study patients. One was a patient with antidepressant non-responding MDD ("Non-R") and another had a non-genetic mitochondrial disorder ("Mito"). The results revealed that serotonin altered the expression of genes related to mitochondrial function and dynamics in neurons and had an equalizing effect on calcium homeostasis in astrocytes, while ATP levels seemed increased. Serotonin significantly decreased cytosolic and mitochondrial calcium in neurons. Electrophysiological measurements evidenced that serotonin depolarized the resting membrane potential, increased both sodium and potassium current density and ultimately improved the overall excitability of neurons. Specifically, neurons from the Non-R patient appeared responsive to serotonin in vitro, which seemed to improve neurotransmission. While it is unclear how this translates to the systemic level and AD resistance mechanisms are not fully elucidated, our observations show that despite his treatment resistance, this patient's cortical neurons are responsive to serotonergic signals. In the Mito patient, evidence suggested that serotonin, by increasing excitability, exacerbated an existing hyperexcitability highlighting the importance of considering mitochondrial disorders in patients with MDD, and avoiding serotonin-increasing medication. Taken together, our findings suggested that serotonin positively affects calcium homeostasis in astrocytes and increases neuronal excitability. The latter effect must be considered carefully, as it could have beneficial or detrimental implications based on individual pathologies.

Association of Depression and Cognitive Performance in US Older Adults: A Secondary Analysis of Cross-Sectional Data Using NHANES 2013-2014

INTRODUCTION

Depression has been associated with cognitive performance, but whether sociodemographic and clinical characteristics might influence this association is not well elaborated. This study aimed to further explore this relationship in older adults.

METHODS

This cross-sectional study is based on data from the National Health and Nutrition Examination Survey (NHANES) 2013-2014. A total of 1,433 individuals with complete information on depressive symptoms and cognitive function variables were included in this study. Patient Health Questionnaire 9 (PHQ-9) score ≥10 as the cutoff to identify cases of depression in our study. We defined poor cognitive performance as a composite cognitive score <47. Logistic regression models were used to examine the association of depression with cognitive performance (model 1). We progressively adjusted the covariates as confounders (model 2: model 1 + age, and gender; model 3: model 2 + race, education level, family income, drinking, and smoking; model 4: model 3 + overweight, arthritis, hyperlipidemia, diabetes, hypertension, heart failure, coronary heart disease, heart attack, stroke, and cancer). We then conducted subgroup, interaction, and restricted cubic spline (RCS) analyses to examine this association.

RESULTS

The prevalence of poor cognitive performance was 36.6% (53/145) in the depression group and 14.1% (182/1,288) in the non-depression group. In the fully adjusted model, depression was significantly associated with poor cognitive performance (adjusted odds ratio: 2.25; 95% confidence interval: 1.31-3.81). The results were robust to sensitivity analyses. Gender and education level may modify the association between depression and poor cognitive performance. RCS analysis revealed that the PHQ-9 score was related to poor cognitive performance in a nonlinear manner (p for nonlinearity <0.001), and exhibited a J-shaped curve.

CONCLUSION

Depression is associated with poor cognitive performance in US older adults. Early recognition and treatment of depression may be potential intervention strategies to protect cognitive health.

Peripheral serotonin levels as a predictor of antidepressant treatment response: A systematic review

There are currently no reliable biomarkers to predict clinical response to pharmacological treatments of depressive disorders. Peripheral blood 5-hydroxytryptamine (5-HT; serotonin) has been suggested as a biomarker of antidepressant treatment response, but there has not been an attempt to systematically summarize and evaluate the scientific evidence of this hypothesis. In this systematic review we searched MEDLINE, Embase, PsycINFO, and the Cochrane Central Register of Controlled Trials. Twenty-six relevant studies investigating peripheral 5-HT as an antidepressant biomarker were identified. In all, we did not find robust support for an association between baseline 5-HT and treatment response. Several larger studies with lower risk of bias, however, showed that higher baseline 5-HT was associated with a greater antidepressant response to SSRIs, prompting future studies to investigate this hypothesis. Our results also confirm previous reports that SSRI treatment is associated with a decrease in peripheral 5-HT levels; however, we were not able to confirm that larger decreases of 5-HT are associated with better treatment outcome as results were inconclusive.

New and emerging treatments for major depressive disorder

Major depressive disorder (MDD) affects a substantial portion of the population; however, much is still unknown about the pathophysiology of this disorder. Treatment resistance highlights the heterogeneous nature of MDD and the need for treatments to target more than monoamine neurotransmission. This review summarizes research into the new and emerging targets of MDD. These include drugs such as psychedelics, antibiotics, opioid modulators, neuropeptides, and onabotulinumtoxin. Neuromodulatory treatments such as light based therapies and neuromodulation involving either magnetic or electrical stimulation are also discussed. Almost all interventions, pharmacological and neuromodulation, were trialed as adjunctive treatments to an antidepressant. Most research has been conducted on psychedelics, with trials suggesting rapid antidepressant and anti-suicidal effects. Trial findings, tolerability, study design limitations and quality of research have been considered throughout this review. There remains challenges in forming recommendations with the current research at present. With there being considerable interest into the research of new and emerging treatments-in particular, psychedelics-there may be scope in the future to form more robust recommendations.

The Role of Water-Soluble Vitamins and Vitamin D in Prevention and Treatment of Depression and Seasonal Affective Disorder in Adults

Depression is a major global health concern expected to worsen by 2030. In 2019, 28 million individuals were affected by depressive disorders. Dietary and supplemental vitamins show overall favorable preventative and therapeutic effects on depression. B vitamins are crucial for neurological function and mood regulation. Deficiencies in these vitamins are linked to depression. Studies on individual B vitamins show promise in improving depressive symptoms, particularly thiamin, riboflavin, niacin, and folate. Vitamin C deficiency may heighten depressive symptoms, but its exact role is not fully understood. Seasonal Affective Disorder (SAD) is associated with insufficient sunlight exposure and vitamin D deficiency. Vitamin D supplementation for SAD shows inconsistent results due to methodological variations. Further investigation is needed to understand the mechanisms of vitamins in depression treatment. Moreover, more research on SAD and light therapy's efficacy and underlying mechanisms involving photoreceptors, enzymes, and immune markers is needed. Although dietary and supplemental vitamins show overall favorable preventative and therapeutic effects on depression, dietitians treating psychiatric disorders face challenges due to diverse study designs, making direct comparisons difficult. Therefore, this article reviews the current literature to assess the role of dietary and supplemental vitamins in the prevention and treatment of depression. This review found that, although evidence supports the role of B vitamins and vitamins C and D in preventing and treating depression, further research is needed to clarify their mechanisms of action and determine the most effective intervention strategies.

B cells and the stressed brain: emerging evidence of neuroimmune interactions in the context of psychosocial stress and major depression

The immune system has emerged as a key regulator of central nervous system (CNS) function in health and in disease. Importantly, improved understanding of immune contributions to mood disorders has provided novel opportunities for the treatment of debilitating stress-related mental health conditions such as major depressive disorder (MDD). Yet, the impact to, and involvement of, B lymphocytes in the response to stress is not well-understood, leaving a fundamental gap in our knowledge underlying the immune theory of depression. Several emerging clinical and preclinical findings highlight pronounced consequences for B cells in stress and MDD and may indicate key roles for B cells in modulating mood. This review will describe the clinical and foundational observations implicating B cell-psychological stress interactions, discuss potential mechanisms by which B cells may impact brain function in the context of stress and mood disorders, describe research tools that support the investigation of their neurobiological impacts, and highlight remaining research questions. The goal here is for this discussion to illuminate both the scope and limitations of our current understanding regarding the role of B cells, stress, mood, and depression.

Adverse childhood experience and depression: the role of gut microbiota

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

An evolutionary analysis of the applicability and utility of the clinico-pathological method in psychiatry

Unlike other medical specialties, psychiatry has not been involved in the theoretical shift that replaced the syndromal approach with the clinico-pathological method, which consists in explaining clinical manifestations by reference to morbid anatomical and physiological changes. Past and present discussions on the applicability of the clinico-pathological method in psychiatry are based on a pre-Darwinian concept of biology as the study of proximate causation. Distinguishing between mediating mechanisms and evolved functions, an evolutionary perspective offers an original contribution to the debate by overcoming the opposite views of dualism (i.e., the clinico-pathological method is not applicable to disorders of the mind) and neuroessentialism (i.e., the definitive way of explaining psychiatric disorders is by reference to the brain and its activity). An evolutionary perspective offers original insights on the utility of the clinico-pathological method to solve critical questions of psychiatric research and clinical practice, including the distinction between mental health and illness, a better understanding of the etiology and pathophysiology, the classification and differential diagnosis of psychiatric disorders, and the development of more efficacious psychiatric treatments.

Struggling Can Also Show on the Inside: Current Knowledge of the Impact of Childhood Maltreatment on Biomarkers in Mood Disorders

The link between childhood maltreatment and mood disorders is complex and involves multiple bio-psycho-social factors that affect multiple molecular pathways. The present narrative review aims to clarify the current understanding of the impact of childhood maltreatment on biomarkers in patients with mood disorders and their first-degree relatives. Neurotransmitters, such as serotonin, dopamine, norepinephrine, and hormones (eg the stress hormone cortisol), play a crucial role in regulating mood and emotion. Childhood maltreatment can alter and affect the levels and functioning of these neurotransmitters in the brain; further, childhood maltreatment can lead to structural and connectivity changes in the brain, hence contributing to the development of mood disorders and moderating illness presentation and modifying response to treatments. Childhood maltreatment information, therefore, appears mandatory in treatment planning and is a critical factor in therapeutic algorithms. Further research is needed to fully understand these pathways and develop new treatment modalities for individuals with mood disorders who have experienced childhood maltreatment and effective preventive interventions for individuals at risk of developing mood disorders.

Brain-Region-Specific Genes Form the Major Pathways Featuring Their Basic Functional Role: Their Implication in Animal Chronic Stress Model

The analysis of RNA-Sec data from murine bulk tissue samples taken from five brain regions associated with behavior and stress response was conducted. The focus was on the most contrasting brain region-specific genes (BRSG) sets in terms of their expression rates. These BRSGs are identified as genes with a distinct outlying (high) expression rate in a specific region compared to others used in the study. The analysis suggested that BRSG sets form non-randomly connected compact gene networks, which correspond to the major neuron-mediated functional processes or pathways in each brain region. The number of BRSGs and the connection rate were found to depend on the heterogeneity and coordinated firing rate of neuron types in each brain region. The most connected pathways, along with the highest BRSG number, were observed in the Striatum, referred to as Medium Spiny Neurons (MSNs), which make up 95% of neurons and exhibit synchronous firing upon dopamine influx. However, the Ventral Tegmental Area/Medial Raphe Nucleus (VTA/MRN) regions, although primarily composed of monoaminergic neurons, do not fire synchronously, leading to a smaller BRSG number. The Hippocampus (HPC) region, on the other hand, displays significant neuronal heterogeneity, with glutamatergic neurons being the most numerous and synchronized. Interestingly, the two monoaminergic regions involved in the study displayed a common BRSG subnetwork architecture, emphasizing their proximity in terms of axonal throughput specifics and high-energy metabolism rates. This finding suggests the concerted evolution of monoaminergic neurons, leading to unique adaptations at the genic repertoire scale. With BRSG sets, we were able to highlight the contrasting features of the three groups: control, depressive, and aggressive mice in the animal chronic stress model. Specifically, we observed a decrease in serotonergic turnover in both the depressed and aggressive groups, while dopaminergic emission was high in both groups. There was also a notable absence of dopaminoceptive receptors on the postsynaptic membranes in the striatum in the depressed group. Additionally, we confirmed that neurogenesis BRSGs are specific to HPC, with the aggressive group showing attenuated neurogenesis rates compared to the control/depressive groups. We also confirmed that immune-competent cells like microglia and astrocytes play a crucial role in depressed phenotypes, including mitophagy-related gene Prkcd. Based on this analysis, we propose the use of BRSG sets as a suitable framework for evaluating case-control group-wise assessments of specific brain region gene pathway responses.

The therapeutic effects of saikosaponins on depression through the modulation of neuroplasticity: From molecular mechanisms to potential clinical applications

Depression is a major global health issue that urgently requires innovative and precise treatment options. In this context, saikosaponin has emerged as a promising candidate, offering a variety of therapeutic benefits that may be effective in combating depression. This review delves into the multifaceted potential of saikosaponins in alleviating depressive symptoms. We summarized the effects of saikosaponins on structural and functional neuroplasticity, elaborated the regulatory mechanism of saikosaponins in modulating key factors that affect neuroplasticity, such as inflammation, the hypothalamic-pituitary-adrenal (HPA) axis, oxidative stress, and the brain-gut axis. Moreover, this paper highlights existing gaps in current researches and outlines directions for future studies. A detailed plan is provided for the future clinical application of saikosaponins, advocating for more targeted researches to speed up its transition from preclinical trials to clinical practice.

Microbiota-Gut-Brain Axis and Antidepressant Treatment

In the treatment of depressive disorders, conventional antidepressant therapy has been the mainstay of clinical management, along with well-established nonpharmacological interventions such as various kinds of psychotherapy. Over the last 2 decades, there has been considerable interest in the role of the gastrointestinal system and its microbiota on brain function, behavior, and mental health. Components of what is referred to as the microbiota-gut-brain axis have been uncovered, and further research has elicited functional capabilities such as "gut-brain modules." Some studies have found associations with compositional alterations of gut microbiota in patients with depressive disorders and individuals experiencing symptoms of depression. Regarding the pathogenesis and neurobiology of depression itself, there appears to be a multifactorial contribution, in addition to the theories involving deficits in catecholaminergic and monoamine neurotransmission. Interestingly, there is evidence to suggest that antidepressants may play a role in modulating the gut microbiota, thereby possibly having an impact on the microbiota-gut-brain axis in this manner. The development of prebiotics, probiotics, and synbiotics has led to studies investigating not only their impact on the microbiota but also their therapeutic value in mental health. These psychobiotics have the potential to be used as therapeutic adjuncts in the treatment of depression. Regarding future directions, and in an attempt to further understand the role of the microbiota-gut-brain axis in depression, more studies such as those involving fecal microbiota transplantation will be required. In addition to recent findings, it is also suggested that more research will have to be undertaken to elicit whether specific strains of gut organisms are linked to depression. In terms of further investigation of the therapeutic potential of prebiotics, probiotics, and synbiotics as adjuncts to antidepressant treatment, we also expect there to be more research targeting specific microorganisms, as well as a strong focus on the effects of specific prebiotic fibers from an individualized (personalized) point of view.

Zuojin pill improves chronic unpredictable stress-induced depression-like behavior and gastrointestinal dysfunction in mice via the theTPH2/5-HT pathway

BACKGROUND

The complex bidirectional communication between the gastrointestinal tract and the brain is associated with mental disorders such as depression; serotonin, as a crucial neurotransmitter in the communication system between the central nervous system and the gastrointestinal tract, has effects on regulating gastrointestinal motility and sensation and improving psychosomatic status. Zuojin pill is used as a traditional Chinese medicine formula for the treatment of gastrointestinal disorders. This study explored the effects of Zuojin pill on the improvement of depression and gastrointestinal function in CUMS mice via TPH2 and its mechanism.

PURPOSE

The aim of this study was to investigate whether Zuojin pill could improve depression and concomitant gastrointestinal dysfunction, and to reveal whether Zuojin pill could work through the regulation of the tryptophan hydroxylase 2 (TPH2) pathway.

METHODS

The CUMS model was established to observe the effects of Zuojin pill on depression-like behavior and gastrointestinal function in mice. Nissler staining and HE staining were used to observe the structure of hippocampal neurons and intestinal mucosa respectively. 5-HT levels in serum, hippocampus, and intestinal tissues were measured by ELISA, and TPH2 expression in hippocampus and intestinal nerves was observed by WB and immunofluorescence. In order to investigate the protective effect and mechanism of Zuojin pill on PC12 cells, CORT used an in vitro model to produce PC12 cell damage.

RESULTS

Our study showed that Zuojin pill ameliorated depression-like behavior and gastrointestinal dysfunction in CUMS mice, elevated BDNF, 5-HT, and TPH2 expression in the hippocampus, and restored the ratio of dopaminergic and GABAergic neurons between intestinal muscles. In vitro experiments showed that Zuojin pill exerted a protective effect on neurons by regulating TPH2 ubiquitination and thus inhibiting CORT-induced apoptosis of PC12 cells.

CONCLUSION

Zuojin pill improves chronic unpredictable stress-induced depression-like behavior and gastrointestinal dysfunction in mice via the TPH2/5-HT pathway. Therefore, TPH2 may be a potential therapeutic target for depression with gastrointestinal dysfunction.

The Serotonin 1A (5-HT1A) Receptor as a Pharmacological Target in Depression

Clinical depression is a common, debilitating and heterogenous disorder. Existing treatments for depression are inadequate for a significant minority of patients and new approaches are urgently needed. A wealth of evidence implicates the serotonin 1A (5-HT1A) receptor in the pathophysiology of depression. Stimulation of the 5-HT1A receptor is an existing therapeutic target for treating depression and anxiety, using drugs such as buspirone and tandospirone. However, activation of 5-HT1A raphe autoreceptors has also been suggested to be responsible for the delay in the therapeutic action of conventional antidepressants such as selective serotonin reuptake inhibitors (SSRIs). This narrative review provides a brief overview of the 5-HT1A receptor, the evidence implicating it in depression and in the effects of conventional antidepressant treatment. We highlight that pre- and post-synaptic 5-HT1A receptors may have divergent roles in the pathophysiology and treatment of depression. To date, developing this understanding to progress therapeutic discovery has been limited, partly due to a paucity of specific pharmacological probes suitable for use in humans. The development of 5-HT1A 'biased agonism', using compounds such as NLX-101, offers the opportunity to further elucidate the roles of pre- and post-synaptic 5-HT1A receptors. We describe how experimental medicine approaches can be helpful in profiling the effects of 5-HT1A receptor modulation on the different clinical domains of depression, and outline some potential neurocognitive models that could be used to test the effects of 5-HT1A biased agonists.