Fibromyalgia is a complex disorder that causes your body to feel widespread pain while also interfering with your memory, mood, energy level, and sleep. Scientists believe that it may be caused by your body processing pain signals incorrectly. They aren't sure what leads to this problem with processing, but there are several theories and possible risk factors.
Fibromyalgia and Neurotransmitters
Because this disorder is believed to be connected to the way your brain processes pain, some scientists have theorized that it may be linked to your brain making too much or too little of a certain neurotransmitter or chemical. Several studies have suggested that people with this condition may have trouble with the way their brains process serotonin, a chemical that aids in relaxation and eases anxiety. Because your brain may have trouble conducting serotonin properly, your body is less relaxed and more vulnerable to pain. Another possible culprit is a neurotransmitter called substance P, which helps your body to perceive pain. Some studies have suggested that patients with the disorder produce three times as much substance P as people without it.
Similar to neurotransmitters, certain stress hormones are also linked to symptoms of the disorder. Researchers have discovered abnormalities in the HPA axis (hypothalamus-pituitary-adrenal gland), a system that controls the stress response and sleep. An impaired stress response could lead to increased feelings of physical and emotional stress, thus causing greater levels of pain. This may be why physical and emotional trauma are linked to later development of the disorder; the high stress may throw the body's stress response system out of order and lead to improper functioning later.
Some patients with the disorder have problems with their muscles that may contribute to pain. The muscles may have thickened capillaries, which reduces blood flow to the muscles and prevents them from getting the nutrients they need. They also tend to have lower levels of chemicals called adenosine triphosphate (ATP) and phosphocreatine, which regulate the flow of calcium to the muscles. Calcium helps muscles relax, so abnormal calcium levels can contribute to tension.
One suggested cause is muscle "microtrauma". These tears in a muscle are so tiny that they're virtually undetectable by doctors but are certainly detectable by your own perceptions of pain. This is another possible explanation for why some people experience symptoms after physical trauma or after certain infections like Lyme disease. If the original injury or disease appears to have healed completely but has left behind muscle microtrauma, it may result in continuing pain.
Although the general consensus is that fibromyalgia causes sleep problems, there's some evidence that it may actually work the other way around. Insomnia disrupts your brain's production of neurotransmitters like serotonin and norepinephrine, so the lack of sleep may cause the decreased pain tolerance. It certainly aggravates symptoms, so addressing your sleep issues will help to relieve your pain.