In the most common type of fibromyalgia, the causes are not known. Physical injuries, emotional trauma, or viral infections such as Epstein-Barr may trigger the disorder, but no one trigger has proven to be a cause of primary fibromyalgia.
Many experts believe that fibromyalgia is not a disease, but is rather a chronic pain condition brought on by several abnormal body responses to stress. Areas in the brain that are responsible for the sensation of pain react differently in fibromyalgia patients than the same areas in healthy people.
People with fibromyalgia have been found to have decreased activity in opioid receptors in parts of the brain that affect mood and the emotional aspect of pain. This reduced response might explain why fibromyalgia patients are likely to have depression, and are less responsive to opioid painkillers, researchers say.
CHRONIC SLEEP DISTURBANCE
Sleep disturbances are common in fibromyalgia. Patients with the condition have a higher-than-average rate of a sleep disorder called periodic limb movement disorder (PLMD). Patients with PLMD involuntarily contract their leg muscles every 20 – 40 seconds during sleep, which may occasionally wake them up.
Some researchers believe that fibromyalgia does not lead to poor sleeping patterns, but that sleep disturbances come first. Researchers continue to investigate the link between fibromyalgia and sleep.
- In one study, healthy volunteers reported fibromyalgia-like pain after their deep sleep had been disrupted. Disturbed sleep appears to trigger factors in the immune system that cause inflammation, pain, fatigue, and lower tolerance to pain. Patients with fibromyalgia have increased rates of cyclic alternating sleep pattern (CAP), which may produce serious sleep problems and have been strongly linked to symptom severity. Previous studies have also suggested that CAP may be related to PLMD.
- Sleep disorders that cause breathing problems are common in women with fibromyalgia.
- Other biological measures of troubled sleep, such as levels of the hormone melatonin (which helps regulate circadian rhythms and the sleep-wake cycle) appear to be normal in most people with fibromyalgia.
BRAIN CHEMICALS AND HORMONAL ABNORMALITIES
Many abnormalities of hormonal, metabolic, and brain chemical activity have been described in studies of fibromyalgia patients. Changes appear to occur in several brain chemicals, although no regular pattern has emerged that fits most patients. Since there has been no clear cause-and-effect relationship established, it may be that fibromyalgia is a result of the effects of pain and stress on the central nervous system, which lead to changes in brain circuitry, rather than a brain disorder itself.
Serotonin. Of particular interest to researchers is serotonin, an important nervous system chemical messenger found in the brain, gut, and other areas of the body. Serotonin plays important roles in creating feelings of well-being, adjusting pain levels, and promoting deep sleep. Serotonin abnormalities have been linked to many disorders, including depression, migraines, and irritable bowel syndrome. Lower serotonin levels have also been noted in some patients with fibromyalgia.