TNF and insomnia: Several genetic variants associated with sleep duration have been identified within the genes involved in cytokine signaling [44], and antagonizing cytokines (such as interleukin-1 (IL-1) and tumor necrosis factor (TNF) in human CNS, as well as upd2 in Drosophila) can increase the risk of insomnia through endocrine and inflammatory regulation [42, 45].