Fibromyalgia and chronic fatigue syndrome (CFS) share certain symptoms, and researchers believe there may be links between the conditions.

Fibromyalgia is a chronic condition that causes widespread musculoskeletal pain.

CFS, which doctors also refer to as myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), is a severe, chronic condition that affects a variety of bodily functions.

Fatigue, widespread pain, sleep issues, and cognitive difficulties are symptoms common to both conditions.

This article looks at the links and differences between the conditions. It also looks at each condition’s causes, diagnoses, and treatments, and answers some frequently asked questions.

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A person can have both conditions, and researchers have found that the two conditions commonly co-occur. One study found that 34% of 313 people with CFS also had fibromyalgia.

As well as commonly coexisting, CFS and fibromyalgia share other similarities, including:

Some researchers argue that the significant overlap between the conditions could mean they are variants of one type of illness, rather than two distinct conditions.

However, other researchers maintain that the differences between the two conditions are significant enough to classify them separately.

These differences include genetic, biochemical, and physiological differences between the two, and different physical and pathological processes.

Although fibromyalgia and CFS can cause similar symptoms, the severity, prevalence, and nature of their symptoms may differ.

Widespread musculoskeletal pain is the primary symptom of fibromyalgia. Although fatigue is a common symptom of the condition, pain all over the body is its main characteristic.

CFS has three core symptoms, which all relate to fatigue. These are:

  • a significant reduction in a person’s ability to do activities they could do before the illness
  • an increase in the severity of CFS symptoms after mental or physical activity, called post-exertional malaise
  • difficulty falling or staying asleep

Pain is a common symptom of CFS, but the location, type, and severity of the pain varies between people, and it is not a defining characteristic of the illness.

Symptoms of fibromyalgia

The symptoms of fibromyalgia include:

Symptoms of CFS

Symptoms of CFS include:

Doctors and medical experts do not know the precise causes of fibromyalgia or CFS. Some factors may increase a person’s risk of developing the conditions, however.

People with fibromyalgia have abnormal pain perception processing. This means they may process physiological stimuli, such as pressure, heat, or cold, as pain, and may be more sensitive to pain than the larger population.

According to the Centers for Disease Control and Prevention (CDC), risk factors for fibromyalgia include:

Some people report developing CFS after having another health issue.

Risk factors for CFS may include:

There are no definitive tests to diagnose CFS or fibromyalgia. A doctor may perform a physical examination, ask questions about a person’s symptoms, and try to rule out other possible causes of symptoms. This may require tests, such as:

  • blood and urine tests
  • sleep studies
  • imaging, such as MRI or CT scans
  • neurological tests

For a fibromyalgia diagnosis, a person’s illness must meet three criteria established by the American College of Rheumatology:

  • no other health condition should be present that could explain the symptoms
  • the symptoms must have been present for at least 3 months
  • a certain level of severity of pain, sleep difficulty, fatigue, and cognitive problems must be present

The diagnostic criteria for CFS include:

  • the presence of the three core symptoms for 6 months or longer
  • the presence of cognitive impairment, worsening of symptoms upon standing up, or both
  • the symptoms should be moderate, substantial, or severe at least half the time

There is no standardized treatment for fibromyalgia or CFS, and the symptoms can vary between individuals.

Treatment for both conditions can include:

There are FDA-approved medications for fibromyalgia, but they often cause side effects. These include:

  • pregabalin
  • duloxetine
  • milnacipran

A person may wish to discuss these medications and their potential side effects with a doctor.

Fibromyalgia and chronic fatigue syndrome (CFS) are similar conditions. Fatigue, widespread pain, sleep issues, and cognitive difficulties are symptoms common to both conditions. A person may have both conditions at the same time.

Musculoskeletal pain characterizes fibromyalgia, while fatigue is the primary symptom of CFS. Experts do not know the exact causes of either condition.

Although fibromyalgia and CFS overlap in several ways, researchers have found various biochemical, genetic, and physiological differences between the two.

Methods of diagnosis and treatment for the conditions can also overlap. Treatment may vary between people, depending on the symptoms and their severity.