The following perspectives were cited in a systematic review by Ma et al., viz., a) Plasma TNF-α levels are significantly increased in some patients with depression; b) Antidepressant treatment is associated with a decrease in TNF-α levels; c) Drug-induced elevation of TNF-α levels cause disease behaviors which are similar to depression, and blocking TNF-α alleviates depressive symptoms in animal models and human clinical trials (140). Here, TNF is linked to major depressive disorder.