For example, a study, using SEM, proposed a model that cortisol (as an indicator of Hypothalamic pituitary adrenal) predicts depression, which predicts circulating pro-inflammatory cytokines (IL-2, IL-6, TNF-α) In patients diagnosed with chronic fatigue syndrome (CFS) [80]. This evidence concerns the gene IL2 and myalgic encephalomeyelitis/chronic fatigue syndrome.