Animal studies suggest that fear inhibits pain whereas anxiety enhances it; however it is unclear whether these effects generalize to humans. The present study examined the effects of experimentally induced fear and anxiety on radiant heat pain thresholds. Sixty male and female human subjects were randomly assigned to 1 of 3 emotion induction conditions: (1) fear, induced by exposure to three brief shocks; (2) anxiety, elicited by the threat of shock; (3) neutral, with no intervention. Pain thresholds were tested before and after emotion induction. Results suggest that findings from animal studies extend to humans: fear resulted in decreased pain reactivity, while anxiety led to increased reactivity. Pain rating data indicated that participants used consistent subjective criteria to indicate pain thresholds. Both subjective and physiological indicators (skin conductance level, heart rate) confirmed that the treatment conditions produced the targeted emotional states. These results support the view that emotional states modulate human pain reactivity.
These results are consistent with a motivational priming model that predicts that unpleasant affective states should enhance pain and that pleasant affective states should attenuate it.
This study was designed to examine the effect of emotion on the nociceptive flexion reflex and pain ratings. To do so, 28 participants viewed pictures varying in emotional valence (unpleasant, neutral, pleasant) and electric stimulations were delivered during and in between pictures. Biceps femoris EMG resulting from the stimulations was used to quantify the nociceptive flexion reflex (spinal nociception), and pain ratings to the stimulations were used as an evaluative measure of supraspinal nociception. Manipulation checks suggested that pictures effectively manipulated emotion. Moreover, nociceptive flexion reflex magnitudes and pain ratings were modulated in a parallel manner. Specifically, viewing unpleasant pictures enhanced the nociceptive flexion reflex and pain, whereas viewing pleasant pictures inhibited the reflex and pain. Analyses suggested that emotional valence, but not arousal, mediated the effects of pictures.
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