Chronic fatigue syndrome (CFS), also referred to as myalgic encephalomyelitis (ME), and often called the "invisible disease", is defined as chronic fatigue that lasts at least six months and cannot be explained by any other illness. This severe disabling disease begins abruptly with a range of flu-like symptoms including muscle fatigue, fevers, lymph-node swelling, persistent diarrhoea, joint and body pain, digestive problems, inability to think, loss of short-term memory and depression. This is followed by months or years of sometimes disabling lethargy ranging to chronic exhaustion and impaired cognition. The controversial and mysterious ailment has gone by various names for more than a century. Most doctors recognize the condition, others are skeptical about its existence, wondering if such fatigue is psychologically perpetuated.
The latest research on what causes chronic fatigue syndrome is testing two hypotheses. One involves previous findings that patients with CFS who have no psychiatric problems have abnormalities in the structure of their brains; the other concerns preliminary data that CFS patients have something wrong with their hearts or blood vessels.
ME/CFS may begin as early as age 10 and as late as age 77. Between 836,000 and 2.5 million Americans suffer from ME/CFS and estimates vary from 17 – 24 million people with ME/CFS worldwide. Although research has shown that ME/CFS is about two to four times more likely to occur in women than men, ME/CFS strikes people from every age, racial, ethnic, and socioeconomic group. Some studies show that ME/CFS may be more common in minority groups.