The additive impact of anxiety and a placebo on pain

We investigated the effects of pain anxiety and a placebo/nocebo/neutral intervention on ice water-induced pain.

We divided 72 volunteers into high- and low-anxiety groups before randomly assigning them to experimental and control subgroups.

Participants completed preimmersion tests of pain anxiety, pain worry, and mood. We scored first immersion pain behavior, experience, and intensity. Each subgroup then received an instruction designed to elicit a positive (placebo), negative (nocebo), or neutral response. After repeating the pain worry test, we gathered second immersion pain scores, and participants repeated the mood test, completed the treatment credibility measure, and were debriefed.

We used the Pain Anxiety Symptom Scale; self-rating Likert-type scales for pain worry, pain intensity, and pain-coping; the Multiple Affect Adjective Checklist (mood); timed measurements for pain threshold and pain tolerance; and a treatment credibility scale.

Pain anxiety and the placebo interventions significantly altered participants' pain scores, with best-to-worse scores reported by the low pain-anxiety/placebo, high anxiety/placebo, low anxiety/neutral, low anxiety/nocebo, high anxiety neutral, and high anxiety/nocebo groups. The high pain-anxiety group demonstrated the greatest response to the placebo/nocebo intervention in the expected directions in pain, worry, and anxious mood scores and in decreased self-confidence in managing pain (this was also negatively affected by the nocebo in each pain-anxiety group).

This study demonstrates that the interaction of the personality variable of pain anxiety with the placebo/nocebo response has an impact on pain, worry, and mood.