IL6 and treatment resistant depression: Kiraly et al. [18] performed a study in which TRD patients, after 4 h since receiving intravenous (iv) ketamine, presented decreased serum levels of interleukin 6 (IL-6) and granulocyte colony-stimulating factor (G-CSF), along with IL-1α and interferon gamma-induced protein 10 (IP-10).