The specific cause of this disease is still not well understood at present. It is postulated that in fibromyalgia, the threshold for pain is lowered because of increased sensitivity of pain signals in the brain. Researchers believe that when repetitive pain signals repeatedly stimulate the brain centers, the concentrations of the chemical substances called neurotransmitters increases in the brain. This causes the brain centers to become sensitive to even minute signals of sensations which are ultimately perceived as pain. The reason behind this sensitization and the reason why it affects some individuals while sparing others is still unknown.