An illness without a known cause that is characterized by long-term exhaustion, muscle weakness, depression, and sleep disturbance. It is often associated with Fibromyalgia and Myofascial Pain Syndrome. It is often precipitated by physical, viral or psychosocial injury or stress.
Chronic fatigue syndrome (CFS) is a syndrome usually accompanied by impairment in short-term memory or concentration, sore throat, tender lymph nodes, muscle or joint pain and headache unrelated to any preexisting medical condition. CFS is characterized as a debilitating and profound syndrome not alleviated by regular bed rest.
a complex disorder characterized by extreme fatigue that lasts six months or longer, and does not improve with rest or is worsened by physical or mental activity. Other symptoms can include weakness, muscle pain, impaired memory and/or mental concentration, and insomnia. The cause is unknown.