What Causes Fibromyalgia Syndrome?

Symptoms of fibromyalgia syndrome (see ‘What is Fibromyalgia?’) include fatigue, with musculoskeletal pain (described as aching or throbbing) and tenderness throughout the body. Other symptoms can include disturbed sleep, stiffness, especially in the morning, migraines, depression, anxiety, stress, acid reflux and irritable bowel syndrome.

Fibromyalgia syndrome can be described as primary or secondary (as a result of another condition), and the causes of primary fibromyalgia syndrome (the most common form) are not clear. There are, however, many theories.

Triggers of Fibromyalgia

There appear to be a number of sets of circumstances that can trigger fibromyalgia syndrome – these are not the underlying cause of the disease, but set off the appearance of the symptoms.

A virus or other infectious agent, which may damage nerves, may trigger fibromyalgia syndrome and causes pain signals to be sent in error. Viruses that may be involved include Lyme's disease, human immunodeficiency virus (HIV, which causes AIDS), Coxsackie B virus and parvovirus B19. Researchers have seen persistent levels of enteroviruses in the muscle of some people with fibromyalgia syndrome, which are not there in healthy volunteers.

Injury and emotional stress both appear to be triggers for fibromyalgia syndrome. In some studies, 25-50% of people with fibromyalgia syndrome report an injury before development of the symptoms. Some physicians suspect exposure to certain drugs and chemicals.

Hormonal changes, for example the menopause, especially if it is early, or a hysterectomy, may also trigger the disorder.

Another disease such as rheumatoid arthritis may trigger fibromyalgia syndrome.

Genetics

Fibromyalgia syndrome seems to run in families – a study of twins confirmed that fibromyalgia syndrome appears to have a genetic background.

Brain Changes and Dysfunction

A number of people with fibromyalgia syndrome show changes in the structure of their brains, which seem to correlate with problems with long- and short-term memory.

A study of the hippocampus (a part of the brain that controls cognitive functions, sleep and pain) showed changes in its function in people with fibromyalgia syndrome.

Cytokines

Some scientists believe that many of the symptoms of fibromyalgia syndrome, especially those associated with sleep disturbance, may be caused by abnormal levels of cytokines. These are chemicals that carry signals between the cells of the immune system.

Neurotransmitters

In fibromyalgia syndrome, levels of different neurotransmitters (chemicals that carry messages between nerve cells) can be too high or too low. These include serotonin (involved in sleep, pain, temperature, appetite, sex drive and mood); norepinephrine (involved in memory and alertness); dopamine (involved in focus and motivation); substance P (help transmit pain messages); and endorphins (produced as a natural ‘antidote’ in response to pain and tiredness).

People with fibromyalgia syndrome may have increased levels of substance P and reduced levels of endorphins, which may explain the increased perception of pain. They also seem to have lower levels of serotonin, which could explain the symptoms of depression and anxiety.

Studies show that in fibromyalgia syndrome, there may be changes in the genes for some neurotransmitters, and these changes are also seen in chronic fatigue syndrome, irritable bowel syndrome and depression.

Vitamin D Deficiency

In studies of people with fibromyalgia syndrome, 83-93% had a vitamin D deficiency – however, many people have a vitamin D deficiency and don’t have fibromyalgia syndrome, so it is unlikely to be a simple link.

Obesity

In a US study, around half of the people with fibromyalgia syndrome were obese, and a further 20% were overweight – however, it is not clear whether obesity is a cause, or is as a result of the disorder.