CXCL8 and depressive symptom measurement: Meta-analyses and systematic reviews corroborate these findings, showing increased levels of interleukin-6 (IL-6), interleukin-8 (IL-8), tumor necrosis factor-alpha (TNF-α), and C-reactive protein (CRP) across major psychiatric disorders, including depression, anxiety, schizophrenia, and BD [31,32].