Chronic fatigue syndrome
Chronic fatigue syndrome (CFS) is an unexplained disease condition that result in severe drowsiness and fatigue that are not alleviated by taking a rest. This disease is also referred to as post-viral fatigue syndrome (PVFS), myalgic encephalomyelitis (ME), or Immune dysfunction syndrome. Chronic fatigue syndrome was first named in the 1980s, but it wasn't called 'disease' by unspecific causes and symptoms. Later, Chronic fatigue syndrome was confirmed as a physical disease through some research.  Although many scientists and researchers tried to find causes of Chronic fatigue syndrome, the causes are still not yet known. However, they found helpful treatments like improvement of depression, present pain, sleeping problems, allergy-like symptoms, and low blood pressure for Chronic fatigue syndrome. 
Causes of Chronic fatigue syndrome have not been found yet, but some experts aim some studies are develop a convergence of conditions like hormone abnormalities, viral or other infections, and physical or emotional conditions. 
Central nervous system and hormone abnormalities have been caused by Chronic fatigue syndrome. Specific chemical's deformed levels in the brain system called the hypothalamus-pituitary-adrenal (HPA) axis which controls things such as sleeping, depression, and stress response are the reason. Some researchers also have found particular factors controlled by the hypothalamus-pituitary-adrenal (HPA) like changes in important neurotransmitters, stress hormone deficiencies, and disturbed circadian rhythms. 
Viral infections can contribute to chronic fatigue syndrome to some people. By the possibility that viral infections can contribute to chronic fatigue syndrome, many researchers always have focused on that. Some specific viruses have been found:
- Herpes virus (human herpes virus 6)
- Epstein-Barr virus
- Cytomegalo virus
- Coxsackie viruses B1 and B4 
Physical and psychological stress can strongly affected chronic fatigue syndrome for many people. Although the relationship between physical and psychological factors has not found specific facts yet, they may make Chronic fatigue increase susceptibility. Moreover, when people don't have enough free radical scavengers like vitamins C, E, and A, their body will become defenseless against cellular destruction. 
Moreover, some researches suggest that these factors can be causes of chronic fatigue syndrome:
Chronic fatigue syndrome has various symptoms from person to person. For this reason, The Centers for Disease Control (CDC) decided to materialize a detailed case definition in 1994. It helps many doctors who try to cure a patient who has Chronic fatigue syndrome. Common symptoms include a flu-like illness, sore throat, memory problems, Intense patterns of headaches, uncomfortable sleeping, and muscle or joint aches. According to CDC, Person who has chronic fatigue syndrome must have four or more of these symptoms. In addition, these symptoms must have appeared during at least 6 months. Other symptoms can include forbearance to alcohol, irritable bowel syndrome, dry eyes and mouth, visual confusion, impaired circulation, and painful menstrual periods. Although some people do get better and recover from it completely, others grow progressively worse. 
The problem related to fatigue usually considered harsh, so it should have four criteria.
- It is not alleviated by sleeping or taking a rest.
- It does not appeared during laborious things related at physical activity.
- It makes people's ability decrease consequently.
- It gets worse after people are sick in mentally and physically. 
There are possible complications to people who have chronic fatigue syndrome.
- Social isolation
- Lifestyle restrictions
- Missing work
- Lack of concentration
- Memory problems 
Chronic fatigue syndrome has no specific characteristics to diagnose; so many people are usually tested with other main causes by a doctor. However, if some symptoms do not only attribute to chronic fatigue syndrome, and also other conditions, it would not be chronic fatigue syndrome. 
It is very complex to manage chronic fatigue syndrome as the disease. Moreover, unfortunately, Chronic Fatigue Syndrome has no standard treatment yet. However, doctors have found ways to alleviate signs and symptoms for individual improvement. For example, some temperate level of daily exercise can help Chronic Fatigue Syndrome. Moreover, treatment of depression, present pain, sleeping problems, allergy-like symptoms, low blood pressure(hypotension), and nervous system problems can make Chronic Fatigue Syndrome better. Some specific therapies like Cognitive behavioral therapy (CBT) and graded exercise therapy (GET)also are known for effective treatment of Chronic fatigue syndrome. 
Furthermore, some studies seek to find new treatments for Chronic Fatigue Syndrome like these medications.
- Methylphenidate (Ritalin)
- Immune globulins and interferon
- Antiviral drugs
- Cholinesterase inhibitors 
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