Chronic fatigue syndrome suggests, this illness is accompanied by six months or more of unexplained fatigue accompanied by following symptoms like cognitive dysfunction, including impaired memory or concentration, postexertional malaise lasting more than 24 hours (exhaustion
and increased symptoms) following physical or mental
exercise, unrefreshing sleep, joint pain (without redness or swelling), persistent muscle pain, headaches of a new type or severity, tender cervical or axillary lymph node