evidence: The decrease in mean number of attacks per day was 0.75 with SJW and 1.01 with placebo, P = 0.06.
intervention: plant extract St. John's Wort (SJW)
comparator: placebo
outcome: E-selectin, metalloproteinase-9 (MMP-9), Granulocyte colony-stimulating factor (G-CSF) , and Vascular endothelial growth factor (VEGF)