Dispositional optimism predicts placebo analgesia

Abstract

Based on prior research identifying dispositional optimism as a predictor of placebo responding, the present study tested the hypothesis that individuals high in optimism would be more likely to respond to a placebo analgesic. Optimists and pessimists were randomly assigned to a placebo expectation condition or a no expectation condition before a cold pressor task. Blood pressure and heart rate were recorded before and during the cold pressor task, and participant ratings of pain and expectations were obtained immediately after the task. Analysis of the expectation manipulation revealed that the placebo instruction was successful in altering participant expectancy during the cold pressor. Supporting the main hypothesis, dispositional optimism was associated with lower pain ratings in the placebo condition but not in the control condition. Because dispositional optimism can alter placebo responding to laboratory pain, future studies should examine the potential role that this individual difference factor may play in patient responsivity to pharmacological and nonpharmacological treatments for clinical pain.

Perspective: This study examined the possibility that individual differences can predict placebo analgesia. Participants were randomly assigned to receive either a placebo expectation or no expectation before a cold pressor task. Dispositional optimism was related to less cold pressor pain in the placebo condition as compared with the control condition.

Figure 1

Scores on the SF-MPQ overall pain index (top panel), ranging from 1 – 4, the SF-MPQ visual analogue scale (middle panel), ranging from 0–100, and the SF-MPQ present pain intensity scale (bottom panel), ranging from 0 – 5, as a function of experimental condition (control condition and placebo condition) and high (+1 SD) and low (−1 SD) dispositional optimism. Higher numbers on the SF-MPQ scales indicates greater pain.