Chronic fatigue syndrome (CFS) is one of several names given to a poorly understood, highly debilitating disorder of uncertain etiology, which is thought to affect approximately 4 per 1,000 adults[1] in the United States and other industrialized countries, and a smaller fraction of adolescents. The disorder is marked by severe, chronic mental and physical exhaustion, arising in a previously healthy and active person, as well as other specific symptoms. Despite promising avenues of research, there remains no objective assay or pathological finding which is widely accepted to be diagnostic of CFS, and it remains a diagnosis of exclusion, made on the basis of patient history and symptomatic criteria. Although there is agreement on the genuine threat to health, happiness, and productivity posed by CFS, various physicians’ groups, researchers, and patient activists champion very different nomenclature, diagnostic criteria, etiologic hypotheses, and favored treatments, resulting in ongoing controversy about nearly all aspects of this enigmatic disorder. Even the name chronic fatigue syndrome is controversial, with some patient advocates and other authorities preferring terms such as myalgic encephalomyelitis ("ME" or "ME/CFS") and post-viral fatigue syndrome ("PVFS"), which imply specific underlying etiologies or pathologic processes.

It should be noted that CFS is not the same as "chronic fatigue” - while fatigue as a symptom is very common, CFS itself is relatively rare by comparison. Most definitions (other than the 1991 UK Oxford criteria) require a number of features, the most common being severe mental and physical exhaustion which is "unrelieved by rest" (according to the 1994 Fukuda definition), and may be worsened by even trivial exertion (a mandatory diagnostic criterion according to some systems). Most diagnostic criteria insist that the symptoms must be present for at least six months, and all insist on there being no other cause for the fatigue: i.e. the fatigue must be idiopathic, not caused by conditions such as radiation treatment for cancer, or diabetes. CFS patients may report many other symptoms which are not included in all diagnostic criteria, including muscle weakness, cognitive dysfunction, hypersensitivity, orthostatic intolerance, digestive disturbances, depression, immune system weakness, and cardiac and respiratory problems. It is unclear if these symptoms represent co-morbid conditions or are produced by the same underlying etiology as CFS itself. Some cases resolve or improve over time, and treatments (though none are universally accepted) bring a degree of improvement to many others.

CFS occurs more often, but not exclusively, in women, for unknown reasons. CFS is most easily diagnosed when formerly active adults become ill, and is most commonly diagnosed in young to middle aged adults, although it is also reported in adolescents and the elderly.

What is meant by "burnout"? What is meant by Chronic Fatigue Syndrome (CFS)?
Many researchers are skeptical about the term "burn out" because it suggests that people cannot recover from this condition, which is wrong. Experts prefer calling this disorder exhaustion/fatigue syndrome. More than half of the patients suffering from this disease suffer also from depression. The difference between those who are exhausted and those who also suffer from depression is that the exhausted ones seldom show symptoms such as self-accusation, thoughts about suicide and decreased appetite. People who are exhausted feel frustrated about their situation.

Fatigue/exhaustion depression or "burnout" is caused by protracted stress, both in private and work life, without any possibility of recovering. This leads to a series of physical and mental symptoms. It may start with pains in the back of the neck, shoulders, back, stomach and chest/heart. It continues with other psychological symptoms such as anxiety and low mood, which can become exhaustion and depression, where even thoughts about suicide can occur.

Fatigue/exhaustion depression and burnout influence cognitive, emotional, behavioral, and physical functions. The most common symptoms are:

emotional fatigue
lack of empathy towards other people's needs
low operational capability
fatigue
lack of energy
irritability
memory lapses, concerning especially short time memory
lack of ability to concentrate
anxiety
low mood
deficient sex lust
insomnia
nerve tension
gastric catarrh
headache
pain

How to treat burnout and exhaustion depression?
Cognitive Therapeutic (CBT) methods have shown the best results in treating burnout and exhaustion depression, but psychodynamic oriented therapy is also used to cure these problems. Therapy based on CBT is based on learning new ways to handle everyday situations, the so-called "coping strategies". This therapy can be conducted successfully in groups. Group therapy has a strong influence on individuals, due to the fact that a group implies social support, which reduces feelings of guilt and shame. The individual does not feel alone with her problems. Individuals may also need to report sick and take antidepressants, depending on how serious the condition is. The time needed to recover varies from a couple of months to several years.

What can you actually do to help yourself?
If you cannot do all the steps below at once, then begin with one activity, then when this works, continue with another activity (one or some days later). More.

Find out the causes behind your stress by keeping a diary. If you see connections between the situations causing stress, try to avoid those situations.
Think about what is important for you in your life in the long run. Compare your life situation today with how you wish it would be and see if there is something you can change immediately.
Try to create a normal life style: eat and sleep at regular times.
Try to stimulate your social life (even outside work) and try to be in environments or groups where you feel appreciated.
Spend some time on your hobbies.
Learn to relax through meditation or yoga.
Exercise a couple of days a week. Try to find a sport that suits you.

Chronic symptoms :
It can be inferred from the 2003 "Canadian" clinical working condition of CFS that there are 8 categories of symptoms:

Fatigue: Unexplained, persistent, or recurrent physical and mental fatigue/exhaustion that substantially reduces activity levels and is not relieved (or not completely relieved) by rest.
Post-exertional malaise: An inappropriate loss of physical and mental stamina, rapid muscular and cognitive fatigability, symptom exacerbation after exertion, plus a pathologically slow recovery period usually 24 hours or longer.
Sleep dysfunction: "Unrefreshing" sleep/rest, poor sleep quantity, insomnia or rhythm disturbances. A study found that most CFS patients have clinically significant sleep abnormalities that are potentially treatable. Sleep patterns may be further interrupted by vivid "feverish" dreams, and unlike in healthy persons, exercise can worsen the sleep dysfunction.
Pain: Pain is often widespread and migratory in nature, including a significant degree of muscle pain and/or joint pain (without joint swelling or redness, and may be transitory). Other symptoms include headaches (particularly of a new type, severity, or duration), lymph node pain, sore throats, and abdominal pain (often as a symptom of irritable bowel syndrome). Patients also report; bone, eye and testicular pain, nerve pain and painful skin sensitivity. Chest pain has been attributed variously to microvascular disease or cardiomyopathy by researchers, and many patients also report painful tachycardia. A systematic review assessing the studies of chronic pain in CFS found that although the exact prevelance is unknown, it is strongly disabling in patients, but unrelated to depression.
Neurological/cognitive manifestations: Common occurrences include confusion, forgetfulness, mental fatigue/brain fog, impairment of concentration and short-term memory consolidation, disorientation, difficulty with information processing, categorizing and word retrieval, and perceptual and sensory disturbances (e.g. spatial instability and disorientation and inability to focus vision), ataxia (unsteady and clumsy motion of the limbs or torso), muscle weakness and "twitches". There may also be cognitive or sensory overload (e.g. photophobia and hypersensitivity to noise and/or emotional overload, which may lead to "crash" periods and/or anxiety).
Autonomic manifestations: Common occurrences include orthostatic intolerance, neurally mediated hypotension (NMH), postural orthostatic tachycardia syndrome (POTS), delayed postural hypotension, lightheadedness, extreme pallor, nausea and irritable bowel syndrome, urinary frequency and bladder dysfunction, palpitations with or without cardiac arrhythmias, and exertional dyspnea (perceived difficulty breathing or pain on breathing).
Neuroendocrine manifestations: Common occurrences include poor temperature control or loss of thermostatic stability, subnormal body temperature and marked daily fluctuation, sweating episodes, recurrent feelings of feverishness and cold extremities, intolerance of extremes of heat and cold, marked weight change anorexia or abnormal appetite, loss of adaptability and worsening of symptoms with stress.
Immune manifestations: Common occurrences include tender lymph nodes, recurrent sore throat, recurrent flu-like symptoms, general malaise, new sensitivities to food and/or medications and/or chemicals (which may complicate treatment).