Deficit of peripheral growth factors in TRD patients. Higher Tie2 levels in TRD patients than controls, while lower VEGFC and BDNF levels in TRD participants. Levels of VEGF were not significantly different between patients and controlsA decrease of VEGF 260 and VEGFC over time in TRD patients was reported. No changes were seen in levels of BDNF following antidepressant treatment. TRD patients showed significantly lower levels of VEGFD at admission compared to responders. This evidence concerns the gene BDNF and treatment resistant depression.