Serum interferon-gamma level is associated with drug-naive major depressive disorder

Objectives: Major depressive disorder is a leading heterogeneous psychiatric illness manifested by persistent low mood, a feeling of sadness, and diminished interest in daily activities. Many biological, genetic, and social factors are thought to be linked with depression. But any suitable early risk assessment markers are absent for this illness. Therefore, we aimed to investigate the serum levels of IFN-gamma in major depressive disorder patients to further investigate the association between serum levels of this cytokine and major depression. Methods: This prospective case-control study enrolled 120 major depressive disorder patients and 100 healthy controls matched by age, sex, and body mass index. A qualified psychiatrist diagnosed the major depressive disorder patients and evaluated healthy controls according to the Diagnostic and Statistical Manual of Mental Health Disorders (5th ed.; DSM-5). The Hamilton depression rating scale was applied for all the study participants to measure the severity of depression. Serum IFN-gamma levels were measured by a commercially available enzyme-linked immunosorbent assay kit (Boster Biological Technology, Pleasanton, CA, USA). Results: This study observed that serum IFN-gamma levels were significantly decreased in major depressive disorder patients compared to healthy controls. A significant negative correlation (r = -0.375; p < 0.001) was obtained between serum IFN-gamma levels and Hamilton depression scores. Receiver operating characteristic analysis showed good diagnostic performance of lowered serum IFN-gamma levels in depression with an area under the curve at 0.790. Conclusion: We suggest the altered serum IFN-gamma levels are associated with the pathophysiology of depression. The reduced levels of serum IFN-gamma might be used as an early risk assessment tool for major depression.