TNF and major depressive disorder: Pro-inflammatory cytokines such as interleukin-1 (IL-1), tumor necrosis factor alpha (TNF-α), and interleukin-6 (IL-6) have been linked to neuroinflammation in illnesses such as Alzheimer’s disease (AD), Parkinson’s disease (PD), depression, and multiple sclerosis (MS) [3,4,5,6].