OBJECTIVE - Elevated trait anger (TRANG; heightened propensity to experience anger) is associated with greater pain responsiveness, possibly via associations with deficient endogenous opioid analgesia. This study tested whether acute anger arousal moderates the impact of TRANG on endogenous opioid analgesia.
METHODS - Ninety-four chronic low back pain (LBP) participants and 85 healthy controls received opioid blockade (8 mg of naloxone) or placebo in a randomized, counterbalanced order in separate sessions. Participants were randomly assigned to undergo either a 5-minute anger recall interview (ARI) or a neutral control interview across both drug conditions. Immediately after the assigned interview, participants engaged sequentially in finger pressure and ischemic forearm pain tasks. Opioid blockade effects were derived (blockade minus placebo condition pain ratings) to index opioid antinociceptive function.
RESULTS - Placebo condition TRANG by interview interactions (p values < .05) indicated that TRANG was hyperalgesic only in the context of acute anger arousal (ARI condition; p values < .05). Blockade effect analyses suggested that these hyperalgesic effects were related to deficient opioid analgesia. Significant TRANG by interview interactions (p values < .05) for both pain tasks indicated that elevated TRANG was associated with smaller blockade effects (less endogenous opioid analgesia) only in the ARI condition (p values < .05). Results for ischemic task visual analog scale intensity blockade effects suggested that associations between TRANG and impaired opioid function were most evident in LBP participants when experiencing anger (type by interview by TRANG interaction; p < .05).
CONCLUSIONS - Results indicate that hyperalgesic effects of TRANG are most prominent when acute anger is aroused and suggest that endogenous opioid mechanisms contribute.