Nomenclature and Definition
The naming of this disease has been contested since its earliest descriptions, and the terminology debate has direct consequences for research funding, clinical recognition, and patient treatment. Myalgic Encephalomyelitis (ME): Coined by Melvin Ramsay in 1956 following the Royal Free Hospital outbreak, the term implies inflammation of the brain and spinal cord (encephalomyelitis). Critics argue that neuropathological evidence for encephalomyelitis is inconsistent, making the name pathologically imprecise. Proponents counter that neuroinflammation (a broader finding than histopathologically-confirmed encephalomyelitis) has since been documented by PET imaging (Section Imaging Studies), though the relationship between PET-detected microglial activation and Ramsay’s original clinical-pathological construct remains debated. Chronic Fatigue Syndrome (CFS): Adopted by the CDC in 1988, this name was intended to be neutral and descriptive. It has been widely criticized for trivializing the disease by emphasizing “fatigue”—a universal human experience—while omitting the hallmark feature of post-exertional malaise. The name has contributed to stigma, with patients reporting that the “fatigue” label leads clinicians and the public to equate ME/CFS with ordinary tiredness or laziness. This is not merely anecdotal: an experimental vignette study (n=143) found that the label “chronic fatigue syndrome” generated significantly more negative attributions—including higher ratings of patients as lazy and less likely to recover—than “myalgic encephalopathy” (Jason et al. 2002). The illness name is an independently demonstrated vector of stigma. ME/CFS: The combined term is now the most widely used in clinical and research literature, adopted by the US NIH, NICE, and most major research institutions. It represents a compromise that acknowledges both historical names while avoiding the implications of either alone. Systemic Exertion Intolerance Disease (SEID): Proposed by the Institute of Medicine (now NAM) in 2015 (Committee on the Diagnostic Criteria for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome 2015) as a replacement name that emphasises the core feature of exercise intolerance. The proposal has not achieved widespread adoption, partly because patients and researchers objected to the word “intolerance” (perceived as implying psychological aversion) and partly because the acronym is unfamiliar. The naming controversy matters because terminology shapes perception. The “chronic fatigue syndrome” label has been associated with medical dismissal (experimentally: CFS label generates more negative attributions than alternative names (Jason et al. 2002)) and has been argued by patient advocates to contribute to reduced research funding relative to disease burden — though funding disparities are multiply determined (no biomarkers, predominantly female patient population, contested nosology) and cannot be attributed to nomenclature alone. Psychogenic framing of ME/CFS was historically reinforced by both the trivializing name and the absence of visible pathology.