Chronic fatigue

Chronic fatigue (CF) is a symptom that can be caused many diseases, illnesses and medications. Chronic fatigue is common in a large number of illnesses including multiple sclerosis, fibromyalgia, rheumatoid arthritis, diabetes, depression, and chronic fatigue syndrome.

Chronic fatigue means the patient experiences significant and long-term fatigue, which may or may not have a known medical explanation. It should be distinguished from the disease called chronic fatigue syndrome (CFS), of which chronic fatigue is only one of many symptoms. The two terms are not interchangeable. Wikipedia contains separate pages for each.

What is a syndrome?
A syndrome is a number of symptoms that commonly occur together, and may or may not be caused by the same underlying disease process.

If there is only one symptom, then the word syndrome cannot be used. For example, Chronic regional pain syndrome involves multiple symptoms including pain (e.g., skin and muscle symptoms) so should not be referred to as chronic pain, which is just one of many symptoms.

Chronic fatigue vs. Chronic fatigue syndrome and Idiopathic Chronic Fatigue


Dr. Jarred Younger explains chronic fatigue and begins by stating "Fatigue is not a disease and it is not even a symptom. So fatigue is a alarm system and the most general alarm system the body has." Webinar with Jarred Younger, Ph.D. (Video starts with quote @6:04 and Younger discusses fatigue until @7:54)

Idiopathic chronic fatigue (ICF) refers to medically unexplained chronic fatigue lasting at least 6 months that does not meet the criteria for chronic fatigue syndrome, for example post-exertional malaise (PEM) may be mild or non-existent, and orthostatic intolerance or cognitive impairment may not be present.

Post-Viral Fatigue vs Post-Viral Fatigue Syndrome
Post-viral Fatigue refers to any Fatigue that started immediately after a virus, whether it is short-term or long-lasting.

Post-Viral Fatigue Syndrome or PVFS is an alternative name for the neurological disease myalgic encephalomyelitis or chronic fatigue syndrome. Post-Viral Fatigue Syndrome is a the main index term used in the World Health Organization's diagnostic manual. Any of the different diagnostic criteria for ME or CFS can be used, provided all the symptoms started together after a viral infection which is now gone.

Examples of incorrect usage
In these examples the neurological disease chronic fatigue syndrome is erroneously referred to using the name of only one of the many symptoms involved, chronic fatigue. Chronic fatigue is a symptom, not a disease. Idiopathic chronic fatigue is the term that should be used to refer to unexplained chronic fatigue. Chronic fatigue is the term to use to refer to long term fatigue which is not necessarily caused by ME/CFS.
 * Feb, 2015, Chronic fatigue IS 'a real and serious disease': Doctors draw up new guidelines on how to diagnose the condition


 * Feb, 2016, How the hell of chronic fatigue drives sufferers to suicide: Those battling condition are SIX times more likely to take their own lives

Notable studies

 * 2002, A factor analysis of chronic fatigue symptoms in a community-based sample (Full text)
 * 2014, Chronic fatigue syndrome: A review (= Balachander Full Text)


 * 2018, Association of sleep disorders, chronic pain, and fatigue with survival in patients with chronic kidney disease: A meta-analysis of clinical trials


 * 2019, Differential diagnosis between “chronic fatigue” and “chronic fatigue syndrome” (Full source)

Learn more

 * 19 Important Causes of Fatigue – Tiredness and Chronic Fatigue Explained
 * Jun 21, 2014, ME/CFS Diagnosis and Name with Dr. Nancy Klimas