MAOA and major depressive disorder: Interestingly, although multiple phenolic acids have anti-depression effect, there is no scientific data that prove that vanillic acid alleviates depression, only several findings on the reduced concentrations of homo-vanillic acid (HVA) in cerebrospinal fluid [42,43,44] and mild inhibition of human MAOA and MAOB from virgin olive oil-extracted vanillic acid [45].