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