Association Between Depression and Elevated C-reactive Protein

Objective: Depression has been related to a higher risk of developing coronary heart disease, but the mechanism that accounts for this association is unclear. Because atherosclerosis is an inflammatory process, depression could increase the risk of coronary heart disease by inducing or promoting inflammation. The objective of the present study was to investigate the association between history of major depressive episode and presence of low-grade systemic inflammation as measured by serum C-reactive protein (CRP).

Methods: We analyzed data from the Third National Health and Nutrition Examination Survey, a representative sample of the US population from 1988 to 1994. Participants included a total of 6149 individuals aged 17 to 39 years who were free of cardiovascular diseases and chronic inflammatory conditions. The main predictor variable of interest was lifetime history of a major depressive episode as assessed by means of the Diagnostic Interview Schedule. The main outcome variable was the presence or absence of an elevated CRP level (> or =22 mg/dl).

Results: Among men, history of a major depressive episode was associated with elevated CRP, particularly for recent episodes (up to 6 months before assessment). In multivariate analyses, men with a history of major depressive episode had 2.77 times higher odds of elevated CRP compared with never-depressed men (95% confidence interval, 1.43-5.26). The adjusted odds ratio was 3.81, 3.98, 1.51, and 1.52 for men who had their last major depressive episode less than 1 month before, 1 to 6 months before, 7 to 12 months before, and more than 12 months before assessment, respectively (p for trend =.004). In women, a comparable association between depression and CRP was quite weak and not significant.

Conclusions: A recent history of major depressive episode is strongly associated with elevated CRP in men aged 17 to 39. In this group, low-grade systemic inflammation could represent a mechanism linking depression to cardiovascular risk.