CFS may develop after what seems to be a typical viral illness. Often, people say that their illnesses started during a time of high stress. In others, CFS develops more slowly. There is no clear illness or other event starting it.

People with CFS say the extreme exhaustion is similar to that felt with mononucleosis, the flu, a lingering hangover, or untreated sleep apnea. The extreme exhaustion of chronic fatigue does not go away. It continues to drain the person for months and years.

Typical symptoms include muscle and joint aches, fatigue, and weakness. Other possible symptoms include belly (abdominal) pain, bloating, chest pain, dizziness, dry eyes or mouth, jaw pain, morning stiffness, night sweats, short-term memory loss, mental problems such as panic attacks, shortness of breath, skin sensations, tingling feelings, and weight loss. CFS symptoms either hang on or often come and go for more than 6 months. For most people, CFS symptoms reach a certain point and stay the same. This happens early in the illness. After that, symptoms switch back and forth between getting worse and getting better. Over time, they may go away.

Anyone can have CFS. People assigned female at birth are about 2 times more likely to develop CFS than people assigned male at birth. But experts aren't sure why this is so. CFS is more common in whites than in people of other ethnic groups. CFS also is known as myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS).

No test has been shown to be able to diagnose CFS. In part, this is because healthcare providers don't know what causes it. In addition, the symptoms are unclear or are a lot like those of other diseases. This makes CFS hard to diagnose even based on the symptoms. A complete history and physical exam are needed to rule out conditions that mimic CFS. In some cases, blood tests may be ordered to rule out diseases like multiple sclerosis and lupus (systemic lupus erythematosus) that take years to show symptoms. Even after a possible diagnosis of CFS, new symptoms might show that the problem is not CFS.

Experts are not sure what causes CFS, but there are many theories. It is clear that CFS is not caused by anemia, hypoglycemia, allergies, or yeast infections. At this time, no one knows the cause. But CFS seems to involve interactions between the immune and central nervous systems. It does not seem to be an infectious disease, passed from one person to another.

No specific treatment is available for CFS. But cognitive behavioral therapy (CBT) and graded exercises may help. CBT uses talk therapy to create strategies to stop negative and unhelpful thought cycles. Graded exercise is exercise therapy that starts slowly and gradually adds more activity over time. Certain medicines can ease some of the symptoms. Nonsteroidal anti-inflammatory drugs (NSAIDs) can ease body aches and fever. Antihistamines can reduce a runny nose and other allergy-like symptoms. Low doses of antidepressants may help with sleep problems and depression from the illness. A rehab specialist can help plan activities for the times when a person with CFS has the energy to do them.

These statements are all rumors that have circulated about CFS, but none has been proved.