Chronic Fatigue Syndrome (Myalgic Encephalomyelitis)

Chronic Fatigue Syndrome (CFS), also known as Myalgic Encephalomyelitis (ME), is a debilitating and potentially disabling illnessFootnote 1-7 that affects over half a million Canadians Footnote * .Footnote 8 CFS/ME is not yet fully understood, but it is known to affect multiple systems of the body. Footnote 1-7


CFS/ME is characterized by Footnote 1-4:

  • unexplained, persistent or recurring fatigue that interferes with normal day-to-day activities and is not relieved by rest;
  • malaise after physical/mental activity (i.e. worsening of symptoms and/or feeling unwell after mild physical/mental activity or even normal physical/mental activity);
  • pain (muscle and/or joint pain, as well as headaches);
  • sleep dysfunction (unrefreshed sleep and/or sleep quantity or rhythm issues);
  • cognitive dysfunction (problems with memory and concentration, feeling 'foggy').

In addition, there may be other nervous and/or immune system responses. These include, but are not limited to Footnote 1-4:

  • tender lymph nodes;
  • gastrointestinal abnormalities;
  • heart rate abnormalities;
  • hypersensitivity to light and sound;
  • mental health conditions, such as depression and anxiety;
  • thermoregulation issues (e.g., feeling feverish or cold in arms and legs).

Symptoms of the disease may vary and their severity might fluctuate over the course of the disease. Footnote 1-4


The causes of ME/CFS are not yet known. Footnote 1,Footnote 2,Footnote 4 Research suggests that an interplay of multiple factors (genetic, environmental, viral/microbial, social, physiological, and psychological) may be responsible for triggering the disease.Footnote 1,Footnote 2,Footnote 4


ME/CFS is hard to diagnose as there are currently no reliable diagnostic tests available. Many of its symptoms overlap with symptoms of other conditions, such as neurological disorders, autoimmune disease, and endocrine disorders. Currently, a diagnosis of ME/CFS is made by ruling out other possible causes of the symptoms experienced. Footnote 1-4


There is currently no cure for ME/CFS. Footnote 1-4 Treatment focuses on managing the symptoms using medications, psychotherapy (for those who experience depression and anxiety), specialised exercise programs, alternative therapies, and lifestyle adjustments. Footnote 1-4

The course of the disease is hard to predict; patients may completely recover, or their symptoms may get better/worse/remain unchanged over time. Footnote 1,Footnote 3,Footnote 4 Relapse after recovery is not uncommon.Footnote 2,Footnote 4

Risk Factors

Women and men of all ages and ethnicities may develop ME/CFS; however, the disease is more common among Footnote 2,Footnote 4,Footnote 9-12:

  • women;
  • people in their 30s, 40s,  and 50s;
  • those who have relatives with ME/CFS;
  • those who have a history of childhood physical and/or emotional trauma.

Related condition – Fibromyalgia

Fibromyalgia is often confused with ME/CFS. While the two conditions are related and may overlap, they are not the same. Footnote 1,Footnote 2 In Fibromyalgia the predominant symptom experienced is pain, whereas in ME/CFS it is fatigue and malaise after physical/mental activity. Footnote 1,Footnote 2

Useful links



Footnote *

Canadians aged 12 years and older

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Footnote 1

Carruthers BM, Jain AK, De Meirleir KL, Peterson DL, Klimas NG, Lerner AM, Bested AC, Flor-Henry P, Joshi P, Powles AP, Sherkey JA. Myalgic encephalomyelitis/chronic fatigue syndrome: clinical working case definition, diagnostic and treatment protocols. Journal of chronic fatigue syndrome. 2003 Jan 1;11(1):7-115.

Return to footnote 1 referrer

Footnote 2

Toward Optimized Practice (TOP) ME/CFS Working Group. Identification and symptom management of myalgic encephalomyelitis/ chronic fatigue syndrome clinical practice guideline. Edmonton, AB: Toward Optimized Practice. 2016.  Available from: and

Return to footnote 2 referrer

Footnote 3

Carruthers BM, van de Sande MI, De Meirleir KL, Klimas NG, Broderick G, Mitchell T, Staines D, Powles AP, Speight N, Vallings R, Bateman L. Myalgic encephalomyelitis: international consensus criteria. Journal of internal medicine. 2011 Oct 1;270(4):327-38.

Return to footnote 3 referrer

Footnote 4

International Association for Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (IACFS/ME). Chronic fatigue syndrome/ myalgic encephalomyelitis: A primer for clinical practitioners. Chicago, IL: International Association for Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (IACFS/ME); 2014. Available from:

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Footnote 5

Hvidberg MF, Brinth LS, Olesen AV, Petersen KD, Ehlers L. The health-related quality of life for patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). PloS one. 2015 Jul 6;10(7):e0132421.

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Footnote 6

Schweitzer R, Kelly B, Foran A, Terry D, Whiting J. Quality of life in chronic fatigue syndrome. Social Science & Medicine. 1995 Nov 1;41(10):1367-72.

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Footnote 7

Hardt J, Buchwald D Wilks D, Sharpe M, Nix WA, Egle UT. Health-related quality of life in patients with chronic fatigue syndrome: an international study. Journal of Psychosomatic Research. 2001 Aug 31;51(2):431-4.

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Footnote 8

Public Health Agency of Canada. Unpublished analysis using 2015 data from the Canadian Community Health Survey (Statistics Canada). 2017

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Footnote 9

Hempel S, Chambers D, Bagnall AM, Forbes C. Risk factors for chronic fatigue syndrome/myalgic encephalomyelitis: a systematic scoping review of multiple predictor studies. Psychological medicine. 2008 Jul 1;38(07):915-26.

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Footnote 10

Heim C, Nater UM, Maloney E, Boneva R, Jones JF, Reeves WC. Childhood Trauma and Risk for Chronic Fatigue SyndromeAssociation With Neuroendocrine Dysfunction. Arch Gen Psychiatry. 2009;66(1):72-80.

Return to footnote 10 referrer

Footnote 11

Albright F, Light K, Light A, Bateman L, Cannon-Albright LA. Evidence for a heritable predisposition to chronic fatigue syndrome. BMC Neurol. 2011;11:62.

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Footnote 12

Salit IE. Precipitating factors for the chronic fatigue syndrome. Journal of psychiatric research. 1997 Feb 28;31(1):59-65.

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