Severe, persisting fatigue is a prominent symptom of Myalgic Encephalomyelitis/chronic fatigue syndrome (ME/CFS), but individuals with this illness frequently report the occurrence of unique fatigue states that might be different from conventional symptoms of fatigue.

individuals with ME/CFS experience different types of fatigue than what are reported in the general populations

the disabling fatigue experienced by individuals with ME/CFS differs from that associated with other illnesses or everyday activity

The finding that ME and CFS group had more functional limitations and more serious symptoms than those with MS [multiple sclerosis] provides additional evidence to the seriousness of ME and CFS.

Myalgic Encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a disabling condition characterized by severe unexplained fatigue and a mixed profile of symptoms such as sore throat, painful/swollen lymph nodes, muscle pain, joint pain, headaches, unrefreshing sleep, post-exertional malaise and cognitive difficulties (K. Fukuda et al., 1994).

Finally, individuals with severe pathological fatigue might experience states that are very different from what a healthy individual experiences when fatigued.