Torture may permanently damage your brain by rewiring its perception of pain, according to a new study. Researchers at Tel Aviv University in Israel have determined that prolonged exposure to pain and suffering can cause abnormalities in the cerebral processes whereby pain stimuli are regulated and organized. The findings may broaden our current understanding of how physical trauma affects the mind.

In current scholarship, pain experience is thought to be controlled by two neuronal processes: pain inhibition and pain excitation. Pain inhibition refers to the mechanism by which one pain is suppressed in response to another. Pain excitation is the degree to which repeated exposure to the same sensation increases the pain felt. The new study, which is published in the European Journal of Pain, sought to investigate whether these processes were altered in torture victims.

To find out, the researchers enrolled 104 Israeli combat veterans of the 1973 Yom Kippur War in an experiment. 60 participants had at some point been prisoners of war (POWs) and suffered burns, severe beating, electric shocks, and starvation. In a series of psychophysical tests, the researchers evaluated each subject’s response to variety of mild pain stimuli. According to lead author Ruth Defrin, the pain responses observed in the POWs differed significantly from those observed in the control group.

"The human body's pain system can either inhibit or excite pain. It's two sides of the same coin," she said in a press release. "Usually, when it does more of one, it does less of the other. But in Israeli ex-POWs, torture appears to have caused dysfunction in both directions. Our findings emphasize that tissue damage can have long-term systemic effects and needs to be treated immediately."

According to the researchers, the POWs’ pain responses indicated an increased pain excitation and a diminished pain inhibition. In other words, the soldiers’ pain intensified faster, and was less likely to subside once a separate pain sensation was introduced. Overall, the POWs exhibited much worse pain regulation than soldiers in the control group.

Given the observed physiological changes, the researchers theorize that many POWs harbor concomitant psychological abnormalities. After all, bodily harm is often accompanied by humiliation, oppression, and other types of verbal abuse. "We think psychological torture also affects the physiological pain system," Defrin told reporters. "We still have to fully analyze the data, but preliminary analysis suggests there is a connection."

Source: R. Defrin, K. Ginzburg, M. Mikulincer, Z. Solomon. The long-term impact of tissue injury on pain processing and modulation: A study on ex-prisoners of war who underwent torture. European Journal of Pain, 2013.