Our group previously demonstrated that changes in mood induced by pleasant or unpleasant odors affect the perceived unpleasantness of painful heat stimuli, without significantly altering perceived pain intensity. In the present study, we examined whether changing mood by viewing emotionally laden visual stimuli also preferentially alters pain unpleasantness. Twelve female subjects immersed their right hand in hot water while observing a video showing a person experiencing the same type of pain (ie, model condition), unpleasant scenes not involving people (ie, disasters condition), or a cityscape video (ie, cityscape condition). Subjects were asked to rate pain intensity, pain unpleasantness, mood, anxiety/calmness, and video unpleasantness, and their skin conductance was measured throughout the experiment. Pain unpleasantness (but not intensity) ratings were higher during the disasters condition, which was associated with the worst mood, than during the cityscape condition; neither mood nor pain unpleasantness was altered in the model video compared with the cityscape video. Moreover, mood was significantly correlated with pain unpleasantness but not with pain intensity. Because these results are similar to those observed when odors were used to alter mood, we conclude that the effects of mood on the affective components of pain are independent of mood induction technique used.
Perspective: This article provides new evidence that changes in mood affect the pain experience by preferentially modulating pain unpleasantness. This finding could potentially help health professionals to treat pain symptoms in patients with altered mood, suggesting methods of pain management aimed at easing the affective, along with the sensory, components of pain.