Theories on the Different Causes of CFS
The cause is not yet known. There are indications, however, that some unknown virus may damage the immune system and predispose people to the illness. There are many theories about the causes of Chronic Fatigue Syndrome. Many experts believe that it develops from a combination of which includes abnormalities of the brain, a hyper-reactive immune system and a viral or other infectious agent. Eventhough all of these factors appear to be at work in many cases of CFS, we still do not yet understand what sequence of events actually leads to the fatigue and the other prominent symptoms of this disorder. Most experts are now positive that genetics play a major role in the disease. In addition, some CFS cases have been found to be caused from other conditions like hypotension, hyperventilation, and defective muscle tissue.
Other causes of CFS are of abnormalities of the Central Nervous System and hormones. Abnormalities in the central nervous system, which includes pinpoint spots of brain inflammation and abnormal levels of certain hormones have been found in a number of CFS patients. However, similar findings have also been found in those without the illness.
Researchers are very interested in possible abnormalities in the brain system known as the Hypothalamus Pituitary Adrenal Axis. This controls a lot of important functions including sleep, response to stress, and depression.
Quite a number of studies on CFS patients have found deficiencies in cortisol levels, a stress hormone, which is produced in the hypothalamus. This hormone is a powerful suppresser of the immune system! One hypothesis of Chronic Fatigue Syndrome suggests that when a person with cortisol deficiency becomes exposed to a viral infection (or some other physical or emotional stress), the immune system overreacts and causes symptoms which are commonly found in CFS. For all that, trial drugs that replace cortisol have reported only limited to moderate improvement in symptoms. Moreover, one study even reported elevated levels of cortisol in the saliva of CFS patients.
On a different note, other researchers have noticed that men with CFS had high levels of serotonin, which is a neurotransmitter or chemical messenger found in the brain. These elevated levels are also associated with fatigue. So if these hormonal imbalances do prove to be prevalent in CFS patients, then the low levels of cortisol and high levels of serotonin may help to set apart Chronic Fatigue Syndrome from major depression which has these hormone levels occurring in opposite directions (high cortisol levels with low serotonin levels). Finally, a different study found that deficiencies in dopamine, which is another important neurotransmitter, might also be another cause of CFS.
There are so many different theories about what causes CFS that it can be truly overwhelming! This is because each CFS case can be different from another CFS case. In many, if not most, instances they have several different causes. The following paragraphs will further explain the different causes of Chronic Fatigue Syndrome.
Immune System Abnormalities
CFS is also referred to as Chronic Fatigue Immune Dysfunction Syndrome, because some studies have found many irregularities of the immune system. Some components appear to be overactive, whereas others appear to be underactive. Researchers have detected a number of immune abnormalities in CFS patients, but no consistent or major abnormality that could indicate a primary cause.
Allergies
Allergies are the only consistent immune system abnormality among CFS patients. Researchers continue to report that between 55% and 80% of CFS patients have allergies to food, pollen, or other substances, which in turn appear to make the CFS symptoms worse. Most allergic people, however, do not have CFS. Some research indicates that in some cases people with both allergies and emotional disorders, such as anxiety or depression, are more vulnerable to the effects of the inflammatory response, which is triggered by allergens. This response produces a number of immune factors, importantly cytokines. These are powerful factors that can cause fatigue, joint aches, and fever and which can affect the hypothalamus-pituitary-adrenal system in the brain. Another recent study found a similar relationship between depression, allergies, and low back pain.
Other Immune Abnormalities
The risk profile for Chronic Fatigue Syndrome, being female, Caucasian, and well-educated, is also the risk profile for auto-immune diseases, such as Systemic Lupus Erythematosus, Rheumatoid Arthritis, Sjogren's Syndrome, and Multiple Sclerosis, which also have early symptoms resembling CFS. These diseases all have in common the presence of high levels of auto-antibodies. These are antibodies that attack the patient's own cells. Some studies are finding high levels of auto-antibodies directed against substances in cell nuclei in CFS patients. Others have found low levels of certain antibodies.
Some patients, particularly those with severe CFS symptoms, have increased numbers of infection-fighting white blood cells known as CD8 killer T cells, which launch attacks on invading viruses and other disease-causing micro-organisms. However, these same people have lower-than-normal numbers of another type of white blood cell, known as the suppresser T cell, which helps to shut down the immune response once the invading organisms have been killed. The immune system then becomes persistently overactive and produces fatigue, muscle aches, and other symptoms of CFS. Other studies have indicated lower amounts of so-called natural killer cells in many CFS patients, which might make them more susceptible to viruses.
Hypotension
Studies are now finding that some people who fit the strict criteria for chronic fatigue syndrome may also have a condition known as Neurally Mediated Hypotension (NMH). One recent study, for example, reported that 25 out of 26 adolescents with CFS experienced NMH. In another small study of patients who met the criteria for CFS, 96% showed signs of NMH compared to only 29% of the comparison group.
NMH causes a dramatic drop in blood pressure when standing up, even for as short a time as ten minutes. It's the result of an abnormality in the central nervous system that signals the heart to slow down and lower blood pressure when a person stands up; blood pools in the feet and legs before circulating back up to the heart, sometimes causing light-headedness, nausea, and fainting.
NMH can explain many of the symptoms of chronic fatigue, although the blood pressure condition is most likely lifelong and chronic fatigue usually occurs in midlife. Some experts believe that in CFS patients, a virus or infection may cause injury to the central nervous system that results in the hypotension abnormality. This could help explain why so many patients report a viral infection before developing chronic fatigue syndrome.
A less severe condition known as postural Orthostatic Tachycardia Syndrome (POTS) is also associated with CFS. Major studies need to be done and the results repeated with larger patient groups before they can be applied to the majority of CFS patients.
Other Theories
Patients with CFS sometimes complain that they feel so weak that it seems as if their muscles are no longer working properly. It has been proposed that a defect in skeletal muscle could be the cause of the fatigue. However, physical, chemical, and metabolic studies have not found any consistent pattern of abnormalities in the muscles of these patients.
Another theory that accounts for some cases of Chronic Fatigue Syndrome is hyperventilation. This is a tendency to over-breathe, which can be caused by many conditions. These include asthma, hyperthyroidism, infections, and anxiety disorder. Chronic hyperventilation may cause an imbalance in oxygen and carbon dioxide, which can produce chest pain, faintness, numbness in the fingers and toes, and motor impairment.
In one study, although a significant number of CFS patients experienced hyperventilation, there were no differences in CFS symptoms between patients with hyperventilation and patients who did not experience it. Furthermore, hyperventilation is very unlikely to be a cause of many instances of chronic fatigue.
Anyway, one study found that after CFS patient's exercise, they exhibit slight abnormalities in the activity of the vagus nerves on the heart. These nerves run down each side of the neck and end at the intestines and affect many bodily functions.
Causes of Gulf War Syndrome
Gulf War veterans have been intensively studied because of a high percentage reporting CFS symptoms. One major study reported that 45% of Gulf War veterans met the overall criteria for Chronic Fatigue Syndrome, with 6% having severe cases.
Women veterans had three times the risk as men. Interestingly, 15% of the non-combat personnel, who represents the general population, reported the same problems. The cases in general were less severe than in the veterans, however.
Since such symptoms have occurred in other veteran groups, some experts suspect that Post-traumatic Stress Syndrome may be responsible for the symptoms in some cases. After finding that stress weakens the blood-brain barrier, some experts believe that, in extremely stressful situations (such as the Gulf War), this weakened barrier may allow agents, such as small viruses, to pass into the brain causing damage and triggering CFS symptoms. Whether uncovering the causes of the syndrome in Gulf War soldiers can be applied to civilian cases of CFS, however, is not known. More than a dozen different illnesses have been detected in over 70,000 soldiers examined for this problem.
Some researchers have identified an unusual bacteria-like organism known as Mycoplasma Fermentans in nearly half the veterans who suffered from Gulf War Syndrome. Moreover, one scientist speculated that it might have even been developed for biological warfare. Some researchers suspect that the symptoms were caused by an experimental vaccine that contained a substance called squalene. High levels of antibodies to this compound have been found in the blood of veterans with CFS symptoms. An investigation is underway.
Still other studies have found that up to 20,000 troops may have been exposed to low levels of sarin nerve gas. In addition, other possible causes among these veterans include multiple immunizations, oil well fires, and sleep apnea. One study reported that the incidence of hospitalization and death was no higher in these veterans than in soldiers who had not been stationed in the Persian Gulf. However, this only proves that the symptoms are not fatal or severe enough to send a patient to the hospital. This study does not disprove the condition itself.
Lastly, a theory that may help tie in the various conditions associated with CFS suggests that a combination of factors, including allergies, stress, and infections, may impair metabolic function by depleting adenosine triphosphate (ATP). This enzyme stores energy in cells, and low levels are common in CFS patients. Furthermore, one study showed symptom improvement using a coenzyme called NADH that increased ATP levels and lends support to this theory.
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