When acute pain turns into chronic, then it is not a symptom of a disease, but it is a disease in itself. It lasts longer than the expected course of the disease or injury. Usual period of 3 to 6 months. In the past the answer to chronic pain was: "everything is in your mind". A useful definition by Margo McCaffrey is: "pain is what describes the person who experiences it and exists when he says he exists."The International Association for the Study of Pain says it is "an unpleasant aesthetic and emotional experience, combined with actual or potential tissue damage, or described in terms of such damage". Pain is transmitted through the body through the nervous system when nerve endings detect damage to a part of the body