Background: The relationship between inflammation and major depressive disorder (MDD) and its associated suicide has been widely debated in recent years.  MDD is one of the most common psychiatric disorders, effects on about 6.7% of adult in every year and it is also one of major causes of suicide. C-reactive protein (CRP) is one of signs of inflammation in body and may have a role as an inflammatory marker in depression and associated suicide.
Objective: To find the association between depression and C-reactive protein.
Patients and Methods: The sample consisted of 25 adult diagnosed with MDD, and 15 adult were not diagnosed with any mental disorder. They were diagnosed clinically according to DSM-5 through a designed semi structured clinical interview and through application of Beck Depression Inventory-II (BDI-II) and Suicidal Probability Scale (SPS), and blood samples were taken to measure plasma level of CRP.
Results: There was a relationship between major depressive disorder and C-reactive protein where it was found that there were statistically significant differences between the cases and control groups in scores of CRP. The mean of cases were 3.88mg/L and control group was 3mg/L with P value 0.019. Moreover, there was a statistically significant difference between CRP level and degree of severity of depression on BDI-II scale. Besides that, there was a relationship in CRP of cases group when compared between depression with suicide ideations and without, yet not a statistically significant. There were also statistically significant differences between cases and controls groups on BDI-II and also on Suicidal Probability Scale (SPS).
Conclusion: C-reactive protein elevated in major depressive disorder patients, and also associated with severity of MDD although this elevation lie in normal range of CRP.