title: A narrative review on the similarities and dissimilarities between myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and sickness behavior.
abstract: It is of importance whether myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a variant of sickness behavior. The latter is induced by acute infections/injury being principally mediated through proinflammatory cytokines. Sickness is a beneficial behavioral response that serves to enhance recovery, conserves energy and plays a role in the resolution of inflammation. There are behavioral/symptomatic similarities (for example, fatigue, malaise, hyperalgesia) and dissimilarities (gastrointestinal symptoms, anorexia and weight loss) between sickness and ME/CFS. While sickness is an adaptive response induced by proinflammatory cytokines, ME/CFS is a chronic, disabling disorder, where the pathophysiology is related to activation of immunoinflammatory and oxidative pathways and autoimmune responses. While sickness behavior is a state of energy conservation, which plays a role in combating pathogens, ME/CFS is a chronic disease underpinned by a state of energy depletion. While sickness is an acute response to infection/injury, the trigger factors in ME/CFS are less well defined and encompass acute and chronic infections, as well as inflammatory or autoimmune diseases. It is concluded that sickness behavior and ME/CFS are two different conditions.
authors.affiliation: Tir Na Nog, Bryn Road Seaside 87, Llanelli SA152LW, UK.
authors.forename: Gerwyn
authors.initials: G
authors.lastname: Morris
authors.forename: George
authors.initials: G
authors.lastname: Anderson
authors.forename: Piotr
authors.initials: P
authors.lastname: Galecki
authors.forename: Michael
authors.initials: M
authors.lastname: Berk
authors.forename: Michael
authors.initials: M
authors.lastname: Maes
mesh_terms: D000818:Animals; D001327:Autoimmune Diseases / Q000453:epidemiology / Q000503:physiopathology / Q000523:psychology; D003863:Depression / Q000175:diagnosis / Q000453:epidemiology / Q000523:psychology; D005221:Fatigue / Q000453:epidemiology / Q000503:physiopathology / Q000523:psychology; D015673:Fatigue Syndrome, Chronic / Q000453:epidemiology* / Q000503:physiopathology / Q000523:psychology; D006801:Humans; D055809:Illness Behavior / Q000502:physiology