The brain seems to be able to generate and uphold sensitization by itself, based on previous experience, or genetic disposition. This seems to be particularly important for muscle pain. There seem to be positive feedback loops where pain produces more pain, and more sensitization. Musculoskeletal pain is the most common pain state. It amounts to almost 50% of all long term sickness absence. But other subjective complaints are also common, and may depend on sensitization. Sensitization has been introduced as an explanation for subjective complaints from the gastrointestinal tract and the brain, like fatigue, tiredness, dizziness, and vertigo. [coderre & katz]