TNF and major depressive disorder: This study showed that ln(PGE2/CRP) and ln(TNF-α/CRP) consistently correlated with TSPO VT (and hence microglial activation and neuroinflammation) in patients with MDD.97 If this approach leads to the identification of peripheral markers that are surrogate markers of neuroinflammation, they can then be used in future RCTs of immunomodulatory therapeutics.