TNF-α Polymorphisms in Major Depressive Disorder in Patients with and Without Cardiovascular Disease: A Systematic Review

Introduction: Major Depressive Disorder (MDD) has been increasingly associated with inflammatory dysregulation, particularly involving tumor necrosis factor-alpha (TNF-α). Genetic polymorphisms within the TNFA promoter region have been investigated as potential modulators of depressive susceptibility, symptom expression, treatment response, and inflammatory comorbidity. However, findings remain inconsistent across populations and clinical contexts. Methods: This systematic review adhered to PRISMA 2020 guidelines and was registered in PROSPERO (CRD420251242724). Observational and interventional studies evaluating associations between TNFA polymorphisms—specifically rs1800629 (−308 G/A), rs1799724 (−857 C/T), and rs1799964 (−1031 T/C)—and MDD-related outcomes in adults were included. Data extraction and methodological quality assessment were performed independently using an adapted GRIPS framework. Results: Eleven studies met the inclusion criteria, with eight investigating MDD without cardiovascular comorbidity and three assessing cardiovascular populations. Across diverse cohorts, rs1800629 and rs1799724 did not demonstrate consistent associations with MDD susceptibility. Although isolated population-specific findings were reported, genotype and allele distributions were generally comparable between cases and controls. Rs1799724 was associated with symptom dimensions and altered TNF-α expression in two cohorts. Rs1799964 was not linked to disease occurrence but showed potential association with antidepressant response and adverse cardiovascular outcomes in patients with chronic heart failure and comorbid depression. Overall, findings were heterogeneous and influenced by population characteristics, sample size, and clinical context. Conclusions: Current evidence does not support a robust etiological role for TNFA promoter polymorphisms in major depressive disorder. These variants may exert context-dependent modulatory effects on symptom expression, treatment response, or inflammatory-cardiovascular interactions rather than serving as primary susceptibility determinants. Larger, ethnically diverse studies integrating genetic, inflammatory, and clinical data are required to clarify the contribution of inflammatory genetic variability in depressive disorders.