Low Back Pain
Additionally there are genetic differences in the responses to stimulation. For example, a metal disc heated to exactly 120° and placed on the forearm will be experienced by some as barely uncomfortable (pain of 1/10) and by others as excruciating (pain of 9/10). Functional brain imaging at the time of the experiment confirms that those who report severe pain actually have greater activation of several areas in the brain that process pain, while those who feel little pain have little brain activation. Thus we conclude that, unless other factors interfere, pain is whatever the patient tells us it is.