Tel Aviv University campus.
(photo credit: PR)
Acute psychological stress lowers a person’s ability to withstand physical pain, according to Tel Aviv University research just published in the journal Pain.
The research, by Prof. Ruth Defrin of the physical therapy department at TAU’s Sackler Faculty of Medicine, showed that sudden stress has a dramatically harmful effect on the body’s ability to modulate (control or modify) pain.
Defrin, working together with TAU doctoral student Nirit Geva and Prof. Jens Pruessner of McGill University, used acute stress tests on a large group of healthy young male adults to evaluate the behavior of the body’s pain modulation mechanisms prior to and after the induction of stress. The team found that although pain thresholds and pain tolerance were apparently unaffected by stress, pain intensified significantly, and there was also a drop in pain inhibition capabilities.
The 29 healthy subjects underwent several commonly accepted pain tests to measure their heat-pain thresholds and pain inhibition.
In one test, for example, to identify their pain thresholds, subjects were asked to signal the moment a gradually increasing heat stimulus became painful.
They underwent a series of pain tests before and immediately after exposure to the Montreal Imaging Stress Task, a computer program of timed arithmetic exercises, designed to induce acute psychosocial stress.
The stress test is a kind of psychological trick – as MIST provides live feedback on submitted responses, registering only 20 percent to 45% of the responses as correct, whether or not a submitted response is the right answer. Because the subject had been previously informed that the average participant tends to score 80% to 90%, he is reminded of his “poor performance,” but he 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, we divided the group according to stress levels,” said Defrin. “We 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.”
She added that “we know from our and others’ previous studies that chronic stress is far more damaging than acute stress, associated not only with dysfunctional pain modulation capabilities but also with chronic pain and systemic illnesses. Stress is defined as a sense of uncontrollability and unpredictability, precisely like being stuck in traffic where you are helpless and have no control over the situation,” said Defrin. “Stress can have positive repercussions in a challenging work environment, for example, but overall it has primarily negative effects.”
The results caused the researchers some surprise: “We were sure we would see an increased ability to modulate pain, because you hear anecdotes about people who are injured during fighting or sports having greater pain modulation,” explained the TAU researcher. “But we were surprised to find quite the opposite. While there was no visible effect of acute stress on the subject’s pain threshold or tolerance, pain modulation decreased in a very dramatic way.”
Modern life exposes individuals to many, recurrent stressful situations, concluded Defrin. “While there is no way to predict the type of stress we will feel under different circumstances, it is advisable to do everything in our power – adopt relaxation and stress reduction techniques as well as therapy – to reduce the amount of stress in our lives.”