Acta Dermato-Venereologica 98-10CompleteContent | Page 9

943 CLINICAL REPORT Nocebo Effects and Scratching Behaviour on Itch Danielle J. P. BARTELS 1,2 , Antoinette I. M. VAN LAARHOVEN 1–3 , Peter C. M. VAN DE KERKHOF 4 and Andrea W. M. EVERS 1–3 1 Health, Medical and Neuropsychology Unit, Institute of Psychology, 2 Leiden Institute for Brain and Cognition (LIBC), 3 Department of Psychiatry, Leiden University Medical Center, Leiden, and 4 Department of Dermatology, Radboud University Medical Center, Nijmegen, The Netherlands Nocebo effects, i.e. reduced treatment effects due to patients’ negative expectations, play a role in itch. Re- cent 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. pla- cebo effects. It is not known whether these effects ge- neralize to itch-associated scratching behaviour. The aim of this study was to determine whether induction and reversal of nocebo effects on itch evoked by elec- trical 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 in- duction or reversal of the nocebo effects, however, no significant nocebo effects or reversed nocebo effects, were found in scratching. Thus, no straightforward ge- neralization of nocebo effects from itch to scratching was found in this laboratory setting. Further investiga- tion into possible generalization is needed in different settings and in patients with chronic itch. Key words: placebo; nocebo; itch; conditioning; verbal sugges- tion; scratching. Accepted May 29, 2018; Epub ahead of print Jun 1, 2018 Acta Derm Venereol 2018; 98: 943–950. Corr: Danielle J. P. Bartels, Health, Medical and Neuropsychology Unit, Leiden University; PO Box 9555; 2300 RB Leiden, The Netherlands. E- mail: [email protected] I tch and scratching are common symptoms in skin con- ditions such as psoriasis and atopic dermatitis, and can cause significant impairment for patients (1). Scratching may have an important role in the maintenance and exa- cerbation of skin conditions due to a vicious itch-scratch circle (2, 3). Effects of pharmacological treatments are relatively limited and these treatments often have side- effects (4). Treatment effectiveness may be improved by optimizing placebo effects, while minimizing nocebo effects (5, 6). Placebo and nocebo effects are positive and negative treatment effects, unrelated to the treatment mechanism, which are induced by patients’ expectations of impro- vement or worsening, respectively (7–9). Placebo and nocebo effects are known to contribute to various condi- tions and symptoms, and have been investigated mainly with regard to pain (7). Recent studies have demonstrated that placebo effects can reduce levels of itch in healthy SIGNIFICANCE Scratching plays an important role in skin conditions due to a vicious itch-scratch cycle. It is known that patients’ expectations regarding a treatment can influence itch in skin conditions by placebo and nocebo effects. We investi- gated whether induced and reversed nocebo effects regar- ding itch also generalize to scratching behavior. Although participants scratched more during itch stimuli of higher intensity, hardly any nocebo effects, or reversed nocebo ef- fects, on scratching were found. Potential generalization of placebo and nocebo effects from itch to scratching should be further investigated to possibly enhance treatments for chronic itch in clinical practice. participants as well as in patients with clinical itch due to chronic conditions (5, 6, 10, 11). Moreover, nocebo effects, which may play an even more important role in clinical practice (8, 12), can amplify itch, and these nocebo effects on itch can also be minimized and even turned into the opposite direction, i.e. a placebo effect (13). Overall, the combination of enhancing placebo ef- fects on itch and reversing nocebo effects seems to be a promising target to further optimize treatment effects for itch. In addition, there are indications that placebo and nocebo effects on a specific symptom can generalize to other modalities or domains (14–19). Thus, nocebo and placebo effects associated with itch treatments may also generalize to the behavioural domain, by which patients’ scratching behaviour (14, 15) may be influenced in a negative or positive direction, respectively. Studies on contagious itch provide some evidence that nocebo-like effects on itch are also seen on scratching be- haviour. For example, when participants watched videos of people scratching compared with control videos, they not only reported higher ratings of overall itch, but also scratched more frequently, with the largest effects for patients with chronic itch (16). However, it is not known whether induced nocebo effects on itch also generalize to scratching behaviour. The aim of this experimental study was to investigate, for the first time, whether induced nocebo effects on itch (electrically induced) generalize to scratching behaviour in healthy participants. As described previously in our article focusing on the levels of itch experienced within the same experiment (13), participants first learned negative expectations about electrical itch stimuli by coupling (through conditioning and verbal suggestions) This is an open access article under the CC BY-NC license. www.medicaljournals.se/acta Journal Compilation © 2018 Acta Dermato-Venereologica. doi: 10.2340/00015555-2979 Acta Derm Venereol 2018; 98: 943–950