MDD patients had higher serum concentrations of TNFα R1. Higher serum concentrations of TNFα R1 in TRD patients than in healthy controls or non-TRD group. The most significant finding from this study was the correlation of increased serum concentrations of TNFα R1 and impaired glutamatergic neurotransmission in the caudate nucleus and anterior cingulate cortex in patients with TRD. Here, TNF is linked to major depressive disorder.