References to an illness with symptoms strongly resembling those of chronic fatigue syndrome can be traced back to as early as 1750. By the 20th century, this condition gained more attention after a series of unexplained epidemics, causing weakness and fatigue, affected large numbers of people. By 1988 the term chronic fatigue syndrome (CFS) was developed as working case definition of the illness.Given that there was no clear biological mechanism, CFS has often been claimed to have a psychological cause and many clinicians have long been sceptical over its existence as a disease entity, often concluding that the disorder is, quite literally, “in a person’s head.”In more recent years robust evidence that chronic fatigue syndrome is in fact, a biological illness has emerged. Researchers have identified distinct immune and brain changes in patients diagnosed with chronic fatigue syndrome.Dr Mark Donohoe has been working with CFS patients for more than two decades. In this first instalment of a two-part podcast series, he discusses the history of CFS , the myriad of underlying contributing factors, how it differs from other types of fatigue, his own valuable clinical observations and much more. Look out next week for Part 2. *****DISCLAIMER: The information provided on FX Medicine is for educational and informational purposes only. The information provided is not, nor is it intended to be, a substitute for professional advice or care. Please seek the advice of a qualified health care professional in the event something you learn here raises questions or concerns regarding your health.*****