Chronic fatigue syndrome: Symptoms, treatment, and causes

Chronic fatigue syndrome is a complex, long-term illness that impacts on a wide range of systems throughout the body. It causes a wide array of symptoms that might present differently for each person with the condition.

The condition is also known as myalgic encephalomyelitis (ME). There might be 17 – 24 million people worldwide with chronic fatigue syndrome (CFS).

Many people who have CFS rely on medical treatment to help alleviate symptoms and may have to learn a new approach to daily living that reduces the impact of the condition.

There is no simple cure, and treatment tends to focus on managing symptoms.


CFS is complex and can impact a wide range of systems and functions.

There is a long list of potential symptoms. Many of these symptoms may appear similar to other conditions, making a thorough diagnosis difficult but important.

Core symptoms

chronic fatigue
Chronic fatigue causes relentless exhaustion among other symptoms.

Doctors first focus on identifying the primary (core) symptoms of the CFS. These may change slightly from person to person, but for a doctor to reach a diagnosis of CFS, they need to note these three of the following core symptoms.


Fatigue is an extreme lack of energy. Doctors officially recognize extreme fatigue as a significantly reduced ability to perform activities that were once routine before the onset of CFS. The fatigue in CFS often lasts 6 months or longer.

In the context of CFS, it is important to note that a doctor does not use “fatigue” to refer to a person feeling tired or unmotivated at a certain point in the day. People with CFS may not be able to shake this fatigue. Sleep or rest does not replenish energy and may even make symptoms worse in some individuals.

The fatigue in CFS may be so severe that it interferes with daily function.

Post-exertional malaise

Post-exertional malaise (PEM) is another core symptom of CFS. PEM is a deterioration of symptoms after physical or mental exertion.

When a person with PEM engages in too much physical or mental activity, they will experience worsening symptoms over the next few hours or days, and will often feel intense exhaustion as they recover.

A person experiencing PEM may describe it as having their internal battery completely and immediately drained. When they push themselves too far, it can harm the body. Therefore, people with CFS must pace themselves throughout the day to avoid overexertion.

Sleep disorders

People with CFS also experience a range of sleep disorders, including unrefreshing sleep. Even after a long night of rest, they wake up tired.

There are a number of sleep disorders that can potentially lead to sleep that does not replenish energy, including:

insomnia, which is trouble falling and staying asleep

hypersomnia, which is excessive sleep

sleep apnea, in which a person stops breathing as they sleep

light sleep, a disorder that means an individual never enters the deeper stages of sleep

fragmented sleep, consisting of frequently waking up and falling back asleep

phase shifting, in which a person may not be able to fall asleep until sunrise

involuntary spasms in the legs or arms

restless legs

nightmares with vivid dreams that disrupt sleep

night sweats

Along with the three above core symptoms that are present, one or both of the following must also be present for the diagnosis of CFS:

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Cognitive impairment

Difficulties with thought processes can occur in many forms for people with CFS.

People with cognitive impairment may have memory problems. They may not be able to remember recent conversations or might always be losing belongings. Movies and books can become extremely difficult to follow all the way through.

Thinking or simple problem solving may severely reduce energy levels in a person with CFS.

Other people with this syndrome may become lost in familiar settings, such as their own neighborhood. They may require intense effort to remember simple directions, names, or even written instructions.

CFS can cause different cognitive impairments in different people.

Orthostatic intolerance

These are symptoms that occur when moving from lying on your back to sitting or standing, including dizziness, lightheadedness, or feeling faint. This also might cause a person to feel as if they are seeing spots or experience blurred vision.

Other symptoms

Other symptoms known to occur in CFS include the following:


Almost all people with CFS experience some form of pain or discomfort, ranging from headaches and cramps to severe, widespread pain.

People with CFS most commonly describe the pain sensation as a general ache or soreness in the muscles and joints. This pain may occur in one area then move to another. Headaches are also common.

Other pain descriptors are common as well, including pain that people describe as:



burning or tingling


Someone with CFS may also be highly sensitive to light, touch, heat, or cold. Experiencing these sensations to an extreme extent may cause pain.

Other potential symptoms

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