CRP and depressive symptom measurement: Meta-analyses have gathered large evidence, particularly with C-reactive protein (CRP) [25, 26], interleukin-6 (IL-6) [23–27], tumour necrosis factor-α (TNF- α) [23, 24, 27] and IL-1 receptor antagonist (IL-1ra) [24–26] being elevated among patients with depression.