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... Show morePlacebo 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. Show less
Nocebo effects, i.e. reduced treatment effects due to patients’ negative expectations, play a role in itch. Recent studies have shown that nocebo effects can be induced experimentally on itch and... Show moreNocebo effects, i.e. reduced treatment effects due to patients’ negative expectations, play a role in itch. Recent studies have shown that nocebo effects can be induced experimentally on itch and also be minimized and even turned into the opposite direction, i.e. placebo effects. It is not known whether these effects generalize to itch-associated scratching behaviour. The aim of this study was to determine whether induction and reversal of nocebo effects on itch evoked by electrical and histamine stimuli generalized to scratching. Ninety-seven healthy participants were included in the study. The manipulation was successful, as during the nocebo learning phase, increased scratching responses were found for higher intensity compared with lower intensity itch stimuli. During the testing phase of induction or reversal of the nocebo effects, however, no significant nocebo effects or reversed nocebo effects, were found in scratching. Thus, no straightforward generalization of nocebo effects from itch to scratching was found in this laboratory setting. Further investigation into possible generalization is needed in different settings and in patients with chronic itch. Show less
Laarhoven, A.I.M. van; Ulrich, D.J.O.; Wilder-Smith, O.H.; Loey, N.E.E. van; Nieuwenhuis, M.; Wee, N.J.A. van der; Evers, A.W.M. 2016
