CRP and major depressive disorder: In patients with depression, the prevalence of high (>3 mg/L) C-reactive protein (CRP) levels, a biomarker for inflammation, has been shown to be 27% (95% CI, 21–34%), whereas, 58% (95% CI, 47–69%) of patients with depression had a mildly elevated CRP level (>1 mg/L) (8).