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A narrative review on the similarities and dissimilarities between myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and sickness behavior

Gerwyn Morris1, George Anderson2, Piotr Galecki3, Michael Berk45678 and Michael Maes49*

Author Affiliations

1 Tir Na Nog, Bryn Road Seaside 87, Llanelli, SA152LW, UK

2 CRC Clinical Research Centre/Communications, Laurel Street 57, Glasgow, G11 7QT,UK

3 Department of Adult Psychiatry, Medical University of Lodz, Aleksandrowska 159, Lodz, 91229, Poland

4 Barwon Health, School of Medicine, Deakin University, PO Box 291, Geelong, 3220, Australia

5 Orygen Youth Health Research Centre, Poplar Road 35, Parkville, 3052, Australia

6 Centre of Youth Mental Health, University of Melbourne, Poplar Road 35, Parkville, 3052, Australia

7 The Florey Institute for Neuroscience and Mental Health, University of Melbourne, Kenneth Myer Building, Royal Parade 30, Parkville, 3052, Australia

8 Department of Psychiatry, University of Melbourne, Level 1 North, Main Block, Royal Melbourne Hospital, Parkville, 3052, Australia

9 Department of Psychiatry, Chulalongkorn University, Rama 4 Road 1873, Pathumwan, Bangkok, 10330, Thailand

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BMC Medicine 2013, 11:64  doi:10.1186/1741-7015-11-64

Published: 8 March 2013


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.

CFS; chronic fatigue; depression; inflammation; ME; oxidative stress; sickness behavior