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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

A converging mechanistic theme across mental disorders involves impaired neuroplasticity and reduced brain-derived neurotrophic factor (BDNF). Glucagon-like peptide-1 receptor agonists (GLP-1RAs), used for type 2 diabetes and obesity, have shown neuroprotective potential, but whether these effects are mediated by BDNF is unclear. This systematic review synthesised molecular evidence linking GLP-1RA administration to BDNF changes and evaluated their contribution to illness progression in neurodegenerative and psychiatric disorders. A systematic search of PubMed, Ovid and Google Scholar from inception to September 6, 2025, identified studies reporting BDNF-related outcomes following GLP-1RA treatment. Eligible studies included primary in vivo or in vitro research on GLP-1RAs in models of neurodegenerative or psychiatric disorders. Risk of bias was assessed using SYRCLE and QUIN tools. The initial search yielded 300 records, of which 18 met the inclusion criteria. Across these studies, GLP-1RAs consistently enhanced BDNF expression and signalling in models of diabetes, neurodegeneration and neurotoxicity, with diabetic models included for their relevance to GLP-1RA pharmacology and shared neuroinflammatory pathway. Reported increases in BDNF expression ranged from 76 % to 377 %, correlating with improved synaptic plasticity, cognition and neuronal survival. In vitro, GLP-1 and exendin-4 increased BDNF expression and axonal transport even under Aβ oligomer exposure. While most neuroprotection aligned with BDNF upregulation, some effects occurred independently through alternative pathways. GLP-1RAs upregulate BDNF in preclinical models, supporting its role as a key mediator of neuroprotection. Despite some BDNF-independent actions, the consistent restoration of neurotrophic support positions BDNF as a central pathway for disease modification. Show less

Growing evidence implicates accelerated biological aging in environmentally induced psychiatric disorders, yet its role in metal-associated depression remains unclear. Using NHANES data, we evaluated associations between heavy metal mixtures and depression. Bidirectional mediation analysis was used to assess reciprocal pathways linking heavy metals, biological aging, and depression. Simultaneously, candidate genes linking heavy metal exposure to depression and biological aging were identified by mining the Comparative Toxicogenomics Database, analyzing differentially expressed genes (DEGs) from the Gene Expression Omnibus, and integrating the resulting evidence within a toxicogenomic framework to explore potential molecular mechanisms. The prevalence of depression among participants was 8.66 %. Metal mixtures significantly increased depression risk. Notably, cadmium and antimony increased the risk of depression (OR: 1.52, 95 % CI: 1.19, 1.94 and OR: 1.54, 95 % CI: 1.22, 1.93). Both metals have low thresholds (0.227 μg/L and 0.053 μg/L, respectively). Additionally, lead, cobalt, and molybdenum showed positive associations in specific models. Although population-level exposure to heavy metals declined from 1999 to 2020, concentrations remained sufficient to elevate depression risk. Our correlation analysis also identified a strong correlation between PhenoAge and chronological age (r = 0.84, P < 0.001). Mechanistically, we found that accelerated PhenoAge partially mediated the associations of several metals with depression risk, including monomethylarsonic acid (β = 0.004; 95 %CI: 0.003,0.006), cadmium (β = 0.006; 95 %CI: 0.003, 0.010), lead (β = 0.009; 95 %CI: 0.006, 0.011), cobalt (β = 0.010; 95 %CI: 0.006, 0.013), molybdenum (β = 0.009; 95 %CI: 0.006, 0.011), and antimony (β = 0.008; 95 %CI: 0.005, 0.011). Pathway analysis and DEGs implicated the contribution of neurodegeneration-multiple diseases pathway, with core molecular targets centering on BDNF, IL6, GSK3B, PTGS2, and SOD1. These findings, which imply biological aging as a potential link between metal exposure and depression, call for revised safety thresholds and pinpoint molecular targets for intervention. Show less