TNF and major depressive disorder: Piletz et al. also reported that MDD patients had higher plasma TNF-α levels compared to healthy subjects, and this value further increased after eight-week venlafaxine treatment [146]; In a follow-up study, total 61 MDD patients received eight-week venlafaxine treatment, and they were divided into responders and non-responders according to the reduction rate of HRSD-17.