IL4 and major depressive disorder: In addition, increased levels of cytokines (IL-6, IL-4, IL-10, and TNF-alpha) and proteins associated with CNS damage and neurotransmitters (epinephrine and serotonin) have been observed in psychiatric conditions such as schizophrenia and depression, which reinforces the role of the neuroendocrine axis as a relevant hypothesis in the occurrence of these disorders related to SARS-CoV-2 infection [55,57].