CRP and major depressive disorder: In PD, increased depressive symptoms as measured by the depression items of HADS and fatigue as measured by FACIT-f correlated with CRP (p = 0.006, β = 0.244 and p = 0.004, β = 0.243, respectively) and SAA (p < 0.001, β = 0.313 and p = 0.006, β = 0.235, respectively) (Fig. 2).