IL6 and major depressive disorder: In systematic reviewsand meta-analyses conducted on youth and adolescents, the levels of peripheralcytokines such as interleukin (IL)-6, C-reactive protein (CRP), and tumornecrosis factor alpha (TNF-α) were found to be high in patients with aclinical diagnosis of depression or anxiety, probably because of the effect ofpsychological and physiological stress on the immune system [5, 6].