Investigation of C-reactive Protein (CRP) in Never-Treated Depressed Patients

Abstract

The relationship between inflammatory markers and depression has been widely debated. C-reactive protein (CRP) is a candidate biomarker for studying such an association. We aim to measure the CRP levels of treatment-naive major depressive disorder (MDD) patients and compare them with those of previously treated MDD patients. This is a cross-sectional study. We recruited 120 patients with MDD; 47 (39.2%) were medication-naïve, while 73 (60.8%) had a history of receiving medication. High-sensitivity CRP in peripheral venous blood was assessed. Subjects were assessed using the Structured Clinical Interview for DSM-IV (SCID-I), the Beck Depression Inventory-II (BDI-II), the Hamilton Anxiety Rating Scale (HAM-A), and the Somatic Symptom Scale-8 (SSS-8). Our results show a statistically significant difference between the two groups in serum CRP levels, with the drug-naïve group having a significantly lower mean CRP level than the group receiving medication. The CRP level was positively correlated with both the number of episodes ( p = 0.006) and the duration of illness ( p = 0.015) in MDD. However, it was not significantly correlated with depression severity or any of its clinical phenotypes. These findings may suggest an underlying pathology of depression that could be either related to the natural course of depressive episodes or a response to antidepressant treatments. This study is one of the few studies to observe a significant difference in the level of CRP in treatment-naïve depressed patients in comparison to those who receive medications. Although the above data are preliminary, the significance of this finding warrants further investigation and replication.