Chronic fatigue syndrome (CFS) causes long-lasting exhaustion and fatigue unalleviated by sleep or rest. In the United States, more than a million people have been diagnosed with CFS. For many, the symptoms of the increasingly common condition reduce their quality of life.

Cognitive Problems

One common symptom of chronic fatigue syndrome is impaired cognitive function. Often, people with the condition have difficulty forming coherent thoughts and expressing them clearly and cohesively. They may feel as if their short-term memory is limited and as though thoughts dissolve in their head. They may find it difficult to talk and understand speech. Some people have also reported difficulty understanding numbers or reading a book.


Erratic Sleep

Another common complaint among people with CFS is erratic sleep patterns. Many people find it difficult to sleep at night despite feeling tired throughout the day, or they may have difficulty waking up in the morning. Some people also experience frequent awakenings throughout the night. Others find they are only able to sleep during certain hours, such as midday, which can wreak havoc on the circadian rhythm. Even a good night's sleep will often not relieve fatigue.


Muscle and Joint Pain

Most people with CFS experience acute or chronic pain and stiffness in the muscles and joints, usually felt in waves that come and go. Joints and muscles may also become stiff and sore, and the pain often has no apparent cause. For many, this kind of pain continues for a few weeks at a time and can greatly interfere with quality of life.



Vertigo is another symptom that some people with CFS experience. They feel dizzy or as though the room is spinning around them. Vertigo can also cause disorientation and blurred vision or tinnitus. Over-the-counter drugs can help ease this symptom, and it can be difficult to recognize vertigo as a sign of chronic fatigue syndrome. Some people with CFS also experience dizziness or lightheadedness when they stand or get up too quickly.



PEM stands for post-exertional malaise, a generalized state of weakness that occurs after physical or mental exertion. By definition, the malaise and weakness last for at least 24 hours after a person exerts themselves. It is one of the classic symptoms associated with CFS, and one of the most debilitating. People who experience PEM typically describe it as a combination of fatigue and achiness. Some people also develop brain fog and flu-like symptoms. PEM normally develops after an intense period of physical or mental activity, such as going on a hike or taking an exam. Sometimes, the onset of PEM takes a few days, and it may persist for days or weeks at a time.


Sensitivity to External Stimuli

People with CFS are especially sensitive to external stimuli such as sounds and smells. A bright advertisement or a sudden loud noise may irritate an individual and may provoke headaches and vomiting. Eye masks and earplugs can help reduce sensitivity, and some people turn to better-insulated walls and light-blocking curtains


Weakened Immune System

Chronic fatigue syndrome can lead to a weakened immune system as the body continuously fails to get enough sleep. This causes an inability to fend off disease and infection as efficiently as a healthy body, which means people with CFS may become sick more often.


Gastrointestinal Problems

People with CFS often have difficulty digesting certain foods. For many, raw vegetables cause intense stomach pain or bloating; for others, consuming meat causes nausea. The consumption of these triggering foods can lead to sharp stabbing pain in the gut, indigestion, and rashes. These individuals often need to remove problematic foods from their diets.



Paresthesia is an abnormal sensation such as tickling, tingling, numbness, and burning on the skin without a physical cause. The symptom may be acute or chronic, but for most people with CFS, it appears at random intervals. Chronic fatigue syndrome can lead people to feel as though bugs are crawling under the skin, or as if a limb has fallen asleep.


Difficulty Staying Upright

Chronic fatigue syndrome can make it difficult for individuals to remain upright for an extended period. Medically, this is known as orthostatic intolerance. When blood pressure drops as someone stands up, the body is not capable of stabilizing itself, leading to dizziness or lightheadedness. Because blood flow does not reach the head quickly enough, people need to sit or lie down to alleviate these symptoms. Some people with orthostatic intolerance also experience headache, weakness, nausea, or sweating when they stand up.


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