Serum Claudin-5 and Peripheral Inflammation in Major Depressive Disorder: A Case-Control Study with Focus on Suicidal Ideation

Reduced serum Claudin-5 in untreated MDD may indicate relatively stable endothelial alterations rather than acute, state-dependent changes. Although Claudin-5 alone had limited prognostic value for suicidality, inflammatory indices-particularly NLR and INFLA-showed stronger associations. Integrating vascular and immune biomarkers may enhance biological stratification and suicide risk assessment in depression and guide future multimodal studies.