Doubling Your Payoff: Winning Pain Relief Engages Endogenous Pain Inhibition

Abstract

When in pain, pain relief is much sought after, particularly for individuals with chronic pain. In analogy to augmentation of the hedonic experience ("liking") of a reward by the motivation to obtain a reward ("wanting"), the seeking of pain relief in a motivated state might increase the experience of pain relief when obtained. We tested this hypothesis in a psychophysical experiment in healthy human subjects, by assessing potential pain-inhibitory effects of pain relief "won" in a wheel of fortune game compared with pain relief without winning, exploiting the fact that the mere chance of winning induces a motivated state. The results show pain-inhibitory effects of pain relief obtained by winning in behaviorally assessed pain perception and ratings of pain intensity. Further, the higher participants scored on the personality trait novelty seeking, the more pain inhibition was induced. These results provide evidence that pain relief, when obtained in a motivated state, engages endogenous pain-inhibitory systems beyond the pain reduction that underlies the relief in the first place. Consequently, such pain relief might be used to improve behavioral pain therapy, inducing a positive, perhaps self-amplifying feedback loop of reduced pain and improved functionality.

Keywords: motivation; pain modulation; perception; relief; reward.

Figure 1.

Time line of one test trial of the wheel of fortune game. The green line in the outcome interval indicates pain relief as the outcome of the game, the red line indicates pain increase as the outcome of the game, and the black line indicates no change as the outcome of the game. Thermal stimulation followed the same temperature time course in both the test and the control trials. Instead of playing the game by choosing a color in the button-press interval in the test trials, participants had to press a black button after which the wheel stopped at a random position with no pointer in the control trials. max., Maximum.

Figure 2.

Means and 95% confidence intervals of behaviorally assessed pain perception for test and control trials in the pain relief, pain increase, and no-change outcomes. Negative values indicate pain sensitization relative to the beginning of each trial, and positive values indicate habituation. post hoc comparisons: *p < 0.017, significant after Bonferroni correction for multiple testing.

Figure 3.

Means and 95% confidence intervals of perceived pain intensity for test and control trials in the pain relief, pain increase, and no-change outcomes. post hoc comparisons: **p < 0.003, *p < 0.017, significant after Bonferroni correction for multiple testing.

Figure 4.

Correlation of participants’ scores on the novelty-seeking subscale of the TCI and pain modulation by pain relief obtained by winning, which was calculated as the difference between intensity ratings in the test minus the control trials of the pain relief outcome.

Figure 5.

Mean amplitudes and 95% confidence intervals of skin conductance responses in the test and control trials in the pain relief, pain increase, and no-change outcomes. post hoc comparisons: ^t*p < 0.10; **p < 0.003 after Bonferroni correction for multiple testing.