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Melatonin, a key regulator of circadian rhythms and sleep-wake cycles, is implicated in the pathophysiology of major depressive disorder (MDD). Emerging evidence supports its anti-inflammatory, cytoprotective, and neuroprotective roles, including promotion of neuroplasticity. This study aims to investigate alterations in serum melatonin, interleukin-6 (IL-6), and brain-derived neurotrophic factor (BDNF) levels in first-episode MDD patients, and explores their clinical correlations. A total of 74 first-episode patients diagnosed with MDD and 72 healthy controls were enrolled in this study. The severity of depressive symptoms was assessed using the 24-item Hamilton Depression Rating Scale (HAMD-24). All blood samples were collected in the morning, and serum levels of melatonin, IL-6, and BDNF were quantified via enzyme-linked immunosorbent assay (ELISA). Baseline serum concentrations of melatonin, IL-6, and BDNF were compared between the MDD group and the control group. Additionally, the discriminative ability of these biomarkers (melatonin, IL-6, and BDNF) in distinguishing MDD patients from healthy controls was evaluated using receiver operating characteristic (ROC) curve analysis. Pearson correlation analysis or Spearman's rank correlation analysis was performed to explore the relationships between serum melatonin levels and clinical disease severity, as well as with IL-6 and BDNF levels, in patients with MDD. Compared with the control group, the MDD group showed significantly higher serum levels of melatonin (Z = -3.861, P < 0.001) and IL-6 (Z = -4.240, P < 0.001), but significantly lower serum BDNF levels (t = 9.537, P < 0.001). Moreover, the combined panel of BDNF, IL-6, and melatonin achieved high accuracy in distinguishing MDD patients from healthy controls, with an area under the curve (AUC) of 0.905. Additionally, no significant correlations were found between serum melatonin levels and clinical disease severity (assessed by HAMD-24 scores), IL-6 levels, or BDNF levels in MDD patients (all P > 0.05). These findings suggest that dysregulation of melatonin, IL-6, and BDNF may contribute to the pathophysiology of first-episode MDD, with their combined measurement offering strong diagnostic potential. Show less

Major Depressive Disorder (MDD) is a multifactorial psychiatric disease influenced by a combination of genetic and environmental factors. Among the genes linked to MDD, the Melanocortin 1 Receptor (MC1R), Catechol-O-Methyltransferase (COMT), Brain-Derived Neurotrophic Factor (BDNF), and the serotonin transporter (5-HTT) are of particular interest due to their critical roles in stress regulation and neural function. Despite their biological significance, the contribution of specific polymorphisms within these genes to MDD risk remains understudied. This retrospective observational case-control study included 87 Colombian patients diagnosed with MDD according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). The control group comprised Latino/admixed individuals without, sourced from the gnomAD v2.1.1 database. The complete coding region of the MC1R gene and three polymorphisms: 5-HTTLPR Insertion/Deletion 44 bp, BDNF-c.196G>A, and COMT-c.472G>A were genotyped using PCR and Sanger sequencing. The polymorphisms rs885479 and rs4680 were identified as protective factors against MDD, while the polymorphisms rs796296176, rs779504604, rs1805005 were associated with an increased risk of developing MDD (OR:22.87, OR:51.26, OR: 1.97, respectively). Several of the analyzed polymorphisms (rs796296176, rs779504604, rs1805005) increase the risk for MDD. Notably, we provide novel evidence of these polymorphisms in MC1R as a risk to MDD. Show less

Major depressive disorder (MDD) is a debilitating neuropsychiatric condition characterized by persistent low mood, affecting approximately 322 million individuals worldwide. With a staggering 15% mortality rate due to suicide among patients, MDD represents a critical global health challenge. Emerging evidence implicates microRNAs (miRNAs) in the pathogenesis of neuropsychiatric disorders; however, the role of miR-146a-3p in MDD-particularly its mechanistic involvement and potential as a diagnostic biomarker-remains unexplored. In this study, we integrated multi-database bioinformatics analyses with experimental validation to identify miR-146a-3p as a key regulator of MDD progression. Our computational screening revealed miR-146a-3p as a putative risk-associated non-coding RNA, alongside brain-derived neurotrophic factor (BDNF), a well-established MDD susceptibility gene. In vivo studies demonstrated a significant upregulation of miR-146a-3p and concurrent downregulation of BDNF in MDD model mice. Further bioinformatic predictions and dual-luciferase reporter assays confirmed a direct interaction between miR-146a-3p and BDNF mRNA, leading to post-transcriptional suppression of BDNF expression. Mechanistically, miR-146a-3p overexpression impaired synaptic plasticity, as evidenced by reduced levels of key synaptic proteins such as postsynaptic density protein 95 (PSD95) and synapsin (SYN-1), while in vitro transfection experiments validated its negative regulation of BDNF. Critically, intranasal delivery of a miR-146a-3p antagomir or exogenous BDNF protein rescued depressive-like behaviors in murine models, as assessed by open-field, forced swim, and tail suspension tests. These interventions restored synaptic protein expression and ameliorated behavioral deficits, suggesting a therapeutic avenue for MDD. Our findings establish miR-146a-3p as a pivotal epigenetic modulator of MDD pathogenesis, acting through direct suppression of BDNF-dependent synaptic plasticity. The reversibility of this pathway via antagomir inhibition highlights miR-146a-3p's dual potential as both a diagnostic biomarker and a therapeutic target. This study provides foundational insights for developing miRNA-based interventions in mood disorders. Show less

Brain-derived neurotrophic factor (BDNF) is a key regulator of neuroplasticity, synaptic integrity and cognitive function and its dysregulation has been implicated across major psychiatric disorders. However, its transdiagnostic association with cognitive performance remains incompletely understood. In this cross-sectional study, 160 participants were examined, including individuals with schizophrenia (SCZ), bipolar disorder (BD), major depressive disorder (MDD) and healthy controls (HC) (n = 40 per group). Serum BDNF concentrations were measured using enzyme-linked immunosorbent assay (ELISA). Cognitive performance was assessed using the Montreal Cognitive Assessment (MoCA), Trail Making Tests (TMT-A/B) and Digit Span (Forward/Backward). Significant group differences were observed for both serum BDNF levels and cognitive performance. Serum BDNF concentrations were lowest in SCZ (18.2 ± 4.6 ng/mL) and MDD (19.5 ± 5.1 ng/mL), intermediate in BD (23.7 ± 5.9 ng/mL) and highest in HC (26.3 ± 6.2 ng/mL) (F(3156) = 15.47, p < 0.001). Cognitive impairment followed a parallel gradient, with SCZ exhibiting the most severe deficits (p < 0.001). Across the full cohort, serum BDNF showed moderate positive associations with global cognition (MoCA: r = 0.42, p < 0.001) and working memory (Digit Span Backward: r = 0.38, p < 0.001) and a negative association with executive dysfunction as indexed by TMT-B completion time (r = -0.46, p < 0.001). These findings indicate that serum BDNF is modestly but consistently associated with cognitive performance across major psychiatric disorders, supporting its role as a transdiagnostic neurobiological correlate of impaired neuroplasticity rather than a disorder-specific or deterministic biomarker. Show less

Diagnosis of affective disorders among adolescent population links with the high risk of suicide attempt. The use of clinical psychological scales and biological markers may help to understand the background of suicidal process. Here we present the exploratory data study on retrospective suicide attempt risk factors and classification model of diagnosis conversion from major depressive disorder to bipolar disorder among adolescent population. This retrospective classification study was conducted on 45 adolescent/early-adulthood patients with the diagnosis of major depressive disorders. The psychological profile of patients was assessed with the use of standard clinical scales, like: Defence Style Questionnaire, Barrat Impulsiveness Scale, Beck Depression Inventory, Family APGAR, Emotional Intelligence Questionnaire and Temperament and Character Inventory. We assessed also the baseline concentration of blood-serum proteins: brain-derived neurotrophic factor, proBDNF, epidermal growth factor, macrophage migration inhibitory protein, and Stem Cell Factor. Suicide attempt history was determined at baseline (lifetime occurrence). The machine learning were used to assess the classification of the risk of suicidal attempt as well as diagnosis conversion from major depression to bipolar disorder. The winning models of machine learning were logistic regression and random forest. Regarding the suicidal attempt risk classification, significant coefficient were found mainly in Hamilton Depression Rating Scale (both factor and item assessment) and Temperament and Character Inventory (AUC = 0.74 (95% CI: 0.53-0.91), permutation p = 0.003). Serum biomarkers showed no discriminative ability (AUC = 0.35-0.40, p > 0.5) for suicide attempts in the past. We found not reliable clinical and biological data on the diagnosis conversion prediction. Clinical psychological scales, not peripheral biomarkers, distinguished suicide attempters in this exploratory analysis. Show less

Electroconvulsive therapy (ECT) proves to be an effective intervention in severe cases of major depressive disorder (MDD), especially when there is resistance to pharmacological treatment. The neurotrophic hypothesis proposes that an increase in brain-derived neurotrophic factor (BDNF) is one of the mechanisms responsible for the therapeutic response. The aim of this study is to investigate the effects of ECT on peripheral levels of BDNF, measured in serum and plasma, and analyze clinical outcomes associated with this intervention, as well as identify methodological variables that may influence findings. A systematic review and meta-analysis of studies published between 1995 and 2025 on the PubMed, Scopus and Web of Science databases were conducted, following Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. Studies of BDNF in serum (14) and plasma (6) were performed separately. Clinical effectiveness was evaluated according to average standardized differences in depression scores. Meta-regressions in the R software identified the impact of four moderators: type of ECT, number of sessions, type of anesthetic and the time blood sample was taken. ECT was associated with an increase in BDNF levels in both biological matrices, especially in studies with plasma (I Show less

Major depressive disorder (MDD) is a prevalent and disabling psychiatric condition in Saudi Arabia, with genetic susceptibility remaining incompletely characterized. Reduced brain-derived neurotrophic factor (BDNF) activity has been implicated in MDD. The Val66Met polymorphism (rs6265), involving the substitution of valine (Val, G allele) with methionine (Met, A allele), impairs activity-dependent BDNF secretion. This study examined the frequency of Val66Met and its association with MDD in a Saudi cohort. A case-control study was conducted, including 87 patients with MDD (44 males, 43 females; mean age 44.2 ± 11.5 years) and 87 healthy controls (39 males, 48 females; mean age 28.7 ± 8.4 years). Genotyping was performed using tetra-primer amplification refractory mutation system-polymerase chain reaction. Unadjusted and age- and sex-adjusted logistic regression analyses were applied under genotype-specific, dominant, recessive, and allelic models. The Val/Val (GG) genotype was more frequent in controls than patients (54.0% vs. 34.5%), whereas the Met/Met (AA) genotype was detected exclusively in patients (21.8% vs. 0%; χ The BDNF Val66Met polymorphism is associated with MDD susceptibility in Saudis. The Met (A) allele, particularly in homozygosity, confers increased risk, while the Val/Val genotype appears protective, supporting population-specific genetic contributions to depression. Show less