Davis KC, Raizen DM. A mechanism for sickness sleep: lessons from invertebrates. J Physiol. 2017 Aug 15;595(16):5415-5424. PMID: 28028818; PubMed Central PMCID: PMC5556163.
From the abstract: "During health, animal sleep is regulated by an internal clock and by the duration of prior wakefulness. During sickness, sleep is regulated by cytokines released from either peripheral cells or from cells within the nervous system. These cytokines regulate central nervous system neurons to induce sleep. Recent research in the invertebrates Caenorhabditis elegans and Drosophila melanogaster has led to new insights into the mechanism of sleep during sickness. ... We will here review key findings that have elucidated the central neuroendocrine mechanism of sleep during sickness. ... We speculate that these mechanisms may play a maladaptive role in human pathological conditions such as in the fatigue and anorexia associated with autoimmune diseases, with major depression, and with unexplained chronic fatigue."