Sustained Low-Grade Pro-inflammatory State in Unmedicated, Remitted Women with Major Depressive Disorder as Evidenced by Elevated Serum Levels of the Acute Phase Proteins C-reactive Protein and Serum Amyloid A

Background: Major depressive disorder (MDD) shows increased coronary artery disease (CAD) risk of unknown mechanism(s). MDD is more common in women than men; CAD diagnosis can be difficult in women. Elevations of the inflammatory markers C-reactive protein (CRP) and serum amyloid A (SAA) predict increased CAD risk in populations; few data on these markers exist in MDD, particularly in remitted patients. Methods: We measured fasting am serum CRP (high sensitivity, CRP_hs) and SAA in 18 unmedicated, remitted women with MDD (mean age 41 ± (SD)12, body mass index (BMI) 25.2 ± 4.1 kg/m²) and 18 BMI-matched healthy control subjects (age 36 ± 10, BMI 25.3 ± 3.8 kg/m²) on 2 separate occasions, ≥ 6 days apart. Results: Repeat SAA and CRP_hs measurements strongly correlated across study days (SAA: r = .83, p < .001; CRP_hs: r = .94, p < .001). Both SAA (5.30 ± 3.39 vs. 2.84 ± 1.87 mg/L, p < .005) and CRP_hs (3.23 ± 3.17 vs. 1.12 ± 1.45 mg/L; p < .01) were significantly elevated in MDD women versus controls. Conclusions: Elevated SAA and CRP_hs in remitted, unmedicated women with MDD indicate a pro-inflammatory state unrelated to current depressive symptoms or pharmacotherapy. These findings suggest that inflammatory mechanisms may in part underlie findings of increased CAD risk in MDD.