The individual logistic regression models, adjusting by age and gender, showed statistically significant overexpression of 17 cytokines (BDNF, HGF, IL-1β, IL-15, IL-17A, IL-18, IL-1RA, IL-2, IL-6, IL-7, IP1b, IP-10, MCP1, PDGFBB, VEGFA, VEGFD, RANTES) in COVID-19 patients, while IFN γ, IL-22, IL-4 and SCF were under-expressed (Figure 1). Here, BDNF is linked to COVID-19.