Physical Pain May Worsen With Stress

Stress is defined as a sense of uncontrollability and unpredictability, and is often the cause of a variety of negative personal, as well as social, effects. Ruth Defrin, from Tel Aviv University (Israel), and colleagues enrolled 29 healthy men in a study in which the subjects underwent several commonly accepted pain tests to measure their heat-pain thresholds and pain inhibition, among other factors. Participants underwent a series of pain tests before and immediately after exposure to the Montreal Imaging Stress Task (MIST), a computer program of timed arithmetic exercises, designed to induce acute psychosocial stress.  MIST provides live feedback on submitted responses, registering only 20-45% of the responses as correct, whether or not a submitted response is the right answer. Because the subject has been previously informed that the average participant tends to score 80%-90%, he is reminded of his “poor performance” but has no way of improving his score, despite his best efforts. This provides the “stress” element of the experiment. To further test the effect of stress on pain, the team divided the group according to stress levels.  The investigators found that not only does psychosocial stress reduce the ability to modulate pain, the changes were significantly more robust among subjects with stronger reaction to stress (‘high responders’). The higher the perceived stress, the more dysfunctional the pain modulation capabilities became. In other words, the type of stress and magnitude of its appraisal determine its interaction with the pain system.  Observing that: “acute psychosocial stress seems not to affect the sensitivity to pain, [but] it significantly reduces the ability to modulate pain in a dose-response manner.,” the study authors submit that: “it appears that the type of stress and the magnitude of its appraisal determine its interactions with the pain system.”