Is serum complement C1q related to major depressive disorder?

Background: Major depressive disorder (MDD) has a high global incidence. While the pathogenesis of depression remains unknown, accumulating evidence has implicated inflammatory changes. Aim: The aim of the study is to compare the serum complement C1q levels in patients with MDD and healthy controls. Setting and Design: The design was a case-control study. Materials and Methods: Blood samples were collected from the patients with MDD and healthy controls to assess the serum C1q levels using an immunotransmission turbidimetric method. Statistical Analysis: Differences in complement C1q levels between patients with MDD and the controls, as well as between sexes among patients with MDD and the controls, were assessed using Mann-Whitney U-test. Spearman correlations were obtained between complement C1q levels and age. Results: In total, 1016 participants (508 MDD and 508 controls) were recruited. Differences in the sex ratio (male/female among controls, 181/327; and MDD, 178/330) and age (controls, 47.0 ± 14.9 years; MDD, 46.5 ± 16.5 years) were not significant. The C1q level in the patients with MDD was significantly higher than that in the healthy controls (P < 0.05). In the MDD group, C1q level correlated significantly with age. Conclusion: Elevation of the serum complement C1q levels in MDD may support the use of C1q as a potential biomarker for diagnosing depression, but further research is needed.