The question "What causes chronic fatigue syndrome?" is a difficult one to answer, in spite of a lot of research. Experts have not been able to pin it on any single cause and believe chronic fatigue syndrome (CFS) could result from multiple factors coming together under the right conditions. These factors may include:
- Genetic factors
- Central nervous system and hormone abnormalities
- A virus or other cause of infection
- Immune system abnormalities
- Psychiatric or emotional conditions
- Toxins
Not everyone with CFS has all of these factors at work in their lives -- they likely have a combination of them that, for some reason, has led to the condition. Because different combinations of factors can cause different symptoms and changes in the body, experts are identifying categories, or subgroups, of CFS.
Identifying a subgroup can help you and your doctor figure out the best way to treat you.
Genetic Factors
Recent research links CFS with genes involved in the hypothalamic-pituitary-adrenal (HPA) axis and the sympathetic nervous system. The HPA axis controls your sleep, response to stress and depression. In the study, researchers looked at DNA that controls how your body reacts to trauma, injury and stress, and they found a common variation that could predict CFS with 76% accuracy. The CDC called this "the first credible evidence of a biological basis for chronic fatigue syndrome." Still, they weren't able to pinpoint genetic markers of chronic fatigue syndrome or determine how the genetic variations influenced symptoms.
In other studies, researchers have discovered genetic abnormalities in people with CFS that influence antibodies and immune function, communication between cells and the ways in which cells get energy.
All of this suggests that some people may be genetically predisposed to developing CFS -- in other words, they're likely to get it if enough triggers come together. Here's an example of how this might work: a genetically predisposed person who is exposed to various risk factors (such as being infected with a particular virus) develops CFS while someone with a different genetic make-up gets the same bug and doesn't.
Central Nervous System & Hormone Abnormalities
As mentioned above, some people with CFS have abnormalities in the HPA axis. Researchers are especially interested in some of the central-nervous-system chemicals and hormones controlled by the HPA axis:
- Neurotransmitter changes
Neurotransmitters are chemicals that communicate messages in your brain. Research has shown that some people with CFS have abnormal levels of certain important neurotransmitters -- serotonin and dopamine. Researchers are working to explain the role these abnormalities play in CFS.
- Stress hormone deficiencies
Experts know levels of the stress hormone cortisol are low in CFS patients, and believe this could be what makes it hard to deal with stress, either physical (such as infection or exertion) or psychological. Cortisol replacement helps some, but not all, CFS patients.
- Disturbed circadian rhythms
Your circadian clock (part of the HPA axis) regulates your sleep-wake cycle. Evidence suggests that some people with CFS this clock is thrown off, possibly by a mentally or physically stressful event, and the body isn't able to get the proper rhythm reestablished. People with this problem appear to spend more time in the REM (rapid-eye movement) phase of sleep, which is when you're dreaming. People in this subgroup of CFS get more help from sleep medications than people in other subgroups, according to experts.
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