There were also significant differences in total white cell count (ANOVA, F3,164 = 4.09; P = 0.008) and absolute number of neutrophils (ANOVA, F3,164 = 3.3; P = 0.022): both were significantly higher in TRD patients compared with controls, and the gradient present for CRP (TRD > drug-free > responsive > controls) was present also for these measures. Here, CRP is linked to treatment resistant depression.