IL6 and depressive disorder: Elevated levels of two pro-inflammatory cytokines, in particular, tumor necrosis factor alpha (TNF) and interleukin 6 (IL6), are observed in patients with Alzheimer’s disease [31], amyotrophic lateral sclerosis [32, 33], multiple sclerosis [34], Parkinson’s disease [35–37], depression disorders [38, 39], and acute patients with schizophrenia or bipolar disorder [40, 41].