Pain has become the United States’ most common health disorder, affecting nearly one out of three Americans, and costing over $40 billion a year in medical bills and lost wages.
The definition of pain recommended by the International Association for the Study of Pain can be qualified as an unpleasant sensory and emotional experience associated with actual or potential tissue damage (Merskey 1979).
Pain is a result of cells and tissues becoming damaged and inflamed; whether it’s from an injury, such as a bruise, or overuse of a muscle, or some other contributing condition or disease, such as arthritis. These damaged cells and tissues exhibit a lack of oxygen and a biological imbalance and generally have a poor blood supply.
Pain is not a simple, straightforward sensory experience, in the manner of, for example, seeing or hearing. This is because pain is both physical and emotional. Pain is caused by the stimulation of special sensory nerve endings that respond to bodily irritation, pressure, heat, cold, injury, stress, and disease.