It's actually a type of neurotransmitter dysfunction. One symptom is a type of dysfunctional sleep called the alpha-delta sleep anomaly. As soon as people with FM reach the deep level sleep, alpha brain waves intrude and jolt them back to shallow sleep. Not only are they denied refreshing sleep, but delta level is when the body does its repair work and chemical replenishment. If people with FM are immobile at any time, such as during travel, or sitting in a meeting, their muscles get rigid and painful.
Morning stiffness can be severe.
Since neurotransmitters affect every part of the body, symptoms can show up all over, and yet the usual medical tests come back negative. FM symptoms fluctuate from hour to hour and day to day, and often worsen with changes in barometric pressure. It's no wonder that FM is one of the most misdiagnosed illness. Doctors often refer FM patients to psychologists or psychiatrists, and yet recent studies show that psychologically, FM patients have about the same amount of abnormal psychology as Rheumatoid Arthritis patients. People with FM have a history of being misunderstood and doubted.