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