CRP and major depressive disorder: Furthermore, individuals with depression, generalized anxiety disorder, and PTSD have higher levels of pro-inflammatory markers (i.e., CRP, IL-1, IL-6, TNF-α) compared to healthy controls.47 IL-6, in particular, appears to play a central role in the relationship between depression and long-term COVID, producing dysregulation between TH17/Treg lymphocytes and sending signals to brain regions implicated in depression such as the anterior cingulate cortex.48