Placebo Effects of Open-label Verbal Suggestions on Itch
Stefanie H. Meeuwis, Henriët van Middendorp, Dieuwke S. Veldhuijzen, Antoinette I.M. van Laarhoven, Jan De Houwer, Adriana P.M. Lavrijsen, Andrea W.M. Evers
Placebo effects are positive outcomes that are not due to active treatment components, which may be elicited even when patients are aware of receiving an inert substance (open-label). This proof-of-principle study investigated for the first time whether open-label placebo effects on itch can be induced by verbal suggestions alone. Ninety-two healthy volunteers were randomized to experimental (open-label suggestions) or control (no suggestions) groups. Self-reported itch evoked by histamine iontophoresis was the primary study outcome. In addition, itch expectations, skin condition and affect were assessed. The experimental group expected lower itch than the control group, which was, in turn, related to less experienced itch in this group only, although no significantly different itch levels were reported between groups. The results illustrate a potential role for open-label placebo effects in itch, and suggest that further study of verbal suggestions through an extensive explanation of placebo effects might be promising for clinical practice.