Diana Álvarez-Mejía

The vagus nerve constitutes a core bidirectional pathway linking the central nervous system with peripheral organs and plays a fundamental role in gut–brain communication. Beyond its classical autonomic functions, accumulating evidence positions vagal signaling as a candidate integrative mechanism through which visceral, immune, and microbial inputs may modulate stress regulation, affective processing, cognition, and neuroplasticity. This narrative review synthesizes current anatomical and physiological knowledge of vagal pathways, with emphasis on afferent projections to the nucleus tractus solitarius and downstream modulation of noradrenergic, serotonergic, and cholinergic circuits involving the locus coeruleus, hippocampus, and prefrontal cortex. We further examine vagus nerve stimulation, including invasive and noninvasive approaches, as a neuromodulatory strategy for neurological and psychiatric disorders. Evidence is reviewed for its effects in epilepsy, mood and anxiety disorders, cognitive impairment, and neurodegenerative conditions, highlighting mechanisms such as synaptic plasticity enhancement, neuroimmune modulation, and regulation of hypothalamic–pituitary–adrenal axis activity. While findings support the translational relevance of vagal modulation, variability in stimulation parameters and outcome measures limits cross-study comparison. Greater methodological standardization and integration of neurocognitive endpoints are required to clarify its clinical and neuroscientific significance.

Background: Major depressive disorder, particularly in its treatment-resistant form, remains a leading cause of global disability. When pharmacotherapy and psychotherapy fail, neuromodulation techniques such as electroconvulsive therapy (ECT) and repetitive transcranial magnetic stimulation (rTMS) are increasingly utilized. However, variability in protocols and outcome reporting continues to generate uncertainty regarding their comparative benefits and safety profiles. Objective: To comprehensively map and synthesize the available evidence on the clinical benefits and adverse effects of ECT and rTMS in adults with major depressive disorder and treatment-resistant depression. Methods: A scoping review was conducted following PRISMA-Sc guidelines and registered in PROSPERO; PubMed–MEDLINE, Scopus, and the Virtual Health Library were searched from inception to October 2022. Observational and experimental studies evaluating ECT and or rTMS in adults with depressive disorders were included. Data were extracted on study design, population characteristics, stimulation parameters, clinical outcomes, and adverse effects. Methodological quality was assessed using National Heart, Lung, and Blood Institute tools. Results: A total of 165 studies comprising 10,701 participants were included. ECT and rTMS were consistently associated with clinically meaningful reductions in depressive symptom severity across heterogeneous protocols. ECT demonstrated the most robust response rates, particularly in treatment-resistant and severe depression, while rTMS showed substantial efficacy with a more favorable safety profile. Adverse effects were more frequent and severe with ECT, including transient cognitive disturbances and cardiovascular complications, whereas rTMS was predominantly associated with mild, self-limited side effects such as headache and scalp discomfort. Considerable heterogeneity in stimulation parameters and diagnostic subgroups was observed across studies. Conclusions: Both ECT and rTMS represent effective neuromodulation strategies for major depressive disorder and treatment-resistant depression. ECT remains the most potent intervention in highly refractory cases, whereas rTMS offers a less invasive alternative with strong tolerability. Standardization of stimulation protocols, biomarker-informed stratification, coadjuvancy analysis, and long-term controlled studies are necessary to refine clinical positioning and advance precision neuromodulation in depression care.

Schizophrenia is a chronic mental disorder affecting approximately 1% of the global population and imposing a significant economic and social burden. In Ecuador, comprehensive data on its incidence, burden, and spatial distribution are scarce. This study aims to estimate the hospital-diagnosed incidence, disease burden, and spatial patterns of schizophrenia in Ecuador using national hospital discharge records from 2010 to 2021. A retrospective observational study was conducted using publicly available hospital discharge records from the Instituto Nacional de Estadística y Censos (INEC). Schizophrenia cases were identified using ICD-10 codes F20–F29. Incidence rates per 100,000 population were estimated with 95% Poisson confidence intervals. Disability-Adjusted Life Years (DALYs) were calculated under three scenarios: no discounting or age weighting, 3%-time discounting, and both. Spatial clusters were identified using SATSCAN software v10.1.2. A total of 10,542 schizophrenia cases were recorded between 2010 and 2021, with an overall incidence rate of 5.36 per 100,000 population (95% CI: 5.26–5.46). Incidence significantly decreased over time (p = 0.029). The estimated burden ranged from 153.05 to 289.78 DALYs per 100,000. High-incidence clusters were identified in Guayas and Pichincha provinces. This study provides the first nationwide assessment of schizophrenia in Ecuador, offering critical insights for health policy development, resource allocation, and improved care strategies.

The intrauterine environment is increasingly recognised as a critical period for the emergence of mental health vulnerabilities. This review explores how adverse maternal exposures, such as psychological stress, infection, malnutrition, and environmental toxins, can disrupt foetal neurodevelopment via epigenetic mechanisms, contributing to the risk of psychiatric and neurodevelopmental disorders. Focusing primarily on human studies, we synthesise evidence on DNA methylation, histone modifications, and non-coding RNAs as key pathways through which the intrauterine environment influences gene regulation in the developing brain. We examine how timing of exposure, foetal sex, and gene–environment interactions modulate these effects, with particular attention to disorders such as schizophrenia, autism spectrum disorder, depression, and anxiety. The placenta emerges as a central mediator, both reflecting and shaping epigenetic changes in response to maternal signals. We also discuss the reversibility of epigenetic marks and highlight emerging interventions, including nutritional supplementation and maternal mental health support, that may buffer or reverse prenatal epigenetic programming. Methodological challenges are addressed, including tissue specificity and causal inference, and future directions are proposed toward integrating epigenetic biomarkers into early risk assessment and precision mental health and psychiatry. This review emphasises the importance of the prenatal period as a window of vulnerability and opportunity for shaping lifelong mental health.

This retrospective observational study aims to evaluate the incidence, disease burden, and geographic distribution of bipolar disorder based on hospital records in Ecuador over an eleven-year span. Hospital discharge data, publicly available from 2011 to 2021, were analyzed to assess incidence, DALYs, and the spatial distribution of hospitalized cases during this period. Between 2010 and 2021, a total of 6,821 hospitalized cases of bipolar disorder were documented in Ecuador, comprising 2,423 males and 4,398 females. The incidence rate peaked in 2019, with the lowest rate reported in 2020. There was no linear association between time and incidence rates or number of cases, but a significant increase was observed from 2017 to 2019 (p < 0.0001). The incidence rate was significantly higher in females compared to males (p < 0.0001). The average annual incidence was 3.47 cases per 100,000 person-years. The mean age at diagnosis was 40.76 years, with females being diagnosed at a younger age than males (p = 0.01548). Bipolar disorder-related deaths totaled 27 (12 males, 15 females). The burden of disease, expressed in DALYs, ranged from 66.769 to 126.98 per 100,000 population, with the hospitals from the private sector contributing most to the average DALYs. YLDs represented over 99% of the total burden. This study highlights the significant gender differences and temporal trends in bipolar disorder incidence in Ecuador, emphasizing the need for targeted public health strategies.

Background/Objectives: The present systematic review analyses the neuroradiological findings in subjects with axis I psychiatric disorders (i.e., bipolar, major depressive, schizophrenic, anxiety, and post-traumatic stress disorders) and comorbid substance use disorder in order to elucidate the organic changes that occur in the brains of people suffering from both conditions. Methods: We analysed and compared the different neuroimaging findings extracted from 93 studies and 10,823 patients; articles were obtained from three databases (Scopus, PubMed [Medline], and the Cochrane Controlled Register of Trials [Central]) and subjected to specific eligibility criteria. We selected articles that assessed patients with axis I psychiatric conditions and a comorbid substance abuse disorder; articles had to report relevant neuroimaging findings and bias was assessed via the Newcastle–Ottawa scale. Results: Significant findings were found on the structure or function of psychiatric patients’ brains with comorbid substance abuse, with certain key areas that were further affected by substance use, especially in areas involved in reward processing, with reductions in volume and connectivity and the augmentation of stimuli-related activity. Conclusions: These results present important implications on the current understanding of psychiatric disorders and comorbid substance use, on the importance of neuroradiological tools in the diagnosis and treatment of these disorders, and on the search for potential new targets for the treatment of psychiatric disease and substance addiction.