Chronic Fatigue Syndrome (CFS) is a health condition typically characterised by symptoms that include extensive periods of lethargy, unexplained aches, and difficulty concentrating, especially following physical exertion.

Due to its complexity and variations in reporting of its symptoms, medical researchers have had a hard time cataloguing the condition. As a result, many individuals experiencing its symptoms have reported challenges in having their state of health taken seriously as a non-psychological illness.

Based on what little is known of the condition, CFS appears to be roughly four times more prevalent in women than in men, with between 17 and 24 million individuals affected worldwide. Treatments often involve various pharmaceuticals and therapy, with mixed results.

Various causes for CFS have been suggested over the decades, and current explanations have linked the illness with disruptions to the immune system, thyroid activity and dysfunctional mitochondria.

As blame moves from purely psychological causes to more complex biological models, improved diagnostic tools and more precise descriptions are set to emerge in coming years.

Is it CFS or ME?

Conditions like CFS that include long durations of extreme levels of fatigue and muscle aches have been described by physicians for centuries.

Since the 1930s, fatigue-based illnesses have been associated with various outbreaks of communicable diseases, such as polio, xenotropic murine leukemia virus-related virus (XMRVB), and Epstein Barr virus. But none provided a definitive diagnosis for a separate condition.

Starting in 1969, with the publication of the eighth edition of the World Health Organisation's International Classification of Disease, chronic fatigue illnesses have been categorised as a form of myalgic encephalomyelitis (ME).

Today, ME and CFS are commonly regarded as the same condition, although there remains controversy about whether the two are actually distinct, or if CFS is an appropriate term at all.

Pinning down a clear definition is difficult as reported symptoms are mixed, causing some to assume the condition is psychological – or at its worst, an invented 'Yuppy Flu' that implies laziness and hypochondria.

Public perceptions of the illness have slowly shifted in recent years, though discrimination and misinformation persist among the public and many physicians to this day.

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