Trait anger expressiveness and pain-induced beta-endorphin release: Support for the oploid dysfunction hypothesis

The anger management styles of anger-in (inhibitio) and anger-out (direct expression) are positively associated with pain responsiveness. Opioid blockade studies suggest that hyperalgesic effects of trait anger-out, but not those of trait anger-in, are mediated in part by opioid analgesic sytem dysfunction. The current study tested the opioid dysfuntion hypothesis of anger-out, using an alternative index of opioid function: pain-induced changes in plasma endogenous opioids. Plasma beta-endorphin (BE) was assessed at rest and again following exposure to three laboratory acute pain tasks (finger pressure, ischemic, and thermal) in 14 healthy controls and 13 chronic low back pain (LBP) subject. As expected, acute pain ratings correlated positively with measures of anger-in (both groups) and anger-out (LBP group; p's <.05). Greater pain-induced increases in BE were associated with significantly lower pain tratings in both groups (p's <.05). Hierarchical multiple regression indicated that greater anger-out significantly predicted smaller pain-induced BE increases (p < 0.5). Subject type did not moderate this association (p > .10). Anger-in did not display significant main or interaction effects on pain-induced BE changes (p's > 0.10). The significant association between anger-out and BE release partially mediated the hyperalgesic effects of anger-out on pain unpleasantness, and was not attenuated by statistical control of general negative effect. This suggests unique associations with expressive anger regulation. Elevated trait anger-out therefore appears to be associated with opioid analgesic system dysfunction, whether it is indexed by responses to opioid blockade or by examining circulating endogenous opioid levels. Possible "state x trait" interactions on these anger-related opioid sytem differences are discussed. (C) 2006 International Association for the Study of Pain. Published by Elsevier B.V All rights reserved.