BDNF and Anxiety: Most importantly, the severity of DF symptoms such as fever, headache, myalgia, arthralgia, retro-/peri-orbital pain, and thrombocytopenia positively correlate with depression and anxiety [16] and increased levels of proinflammatory cytokines such as Interleukin 4/6 and tumor necrosis factor (TNF)-alpha, and platelet brain-derived neurotrophic factors (BDNF) account for the presence of depressive and anxiety symptoms among adult patients with DF [16].