The study objective is to assess whether negative and positive outcome expectations, induced by verbal suggestions under both open- and closed-label conditions, can influence itch during a short-term validated histamine test. Additionally, we…
ID
Source
Brief title
Condition
- Other condition
Synonym
Health condition
Het onderzoek wordt bij gezonde proefpersonen uitgevoerd. Uitkomsten uit deze lijn van onderzoek bieden nieuwe handvatten voor verklaringsmodellen en therapeutische interventies voor aandoeningen waarbij jeuk een symptoom is.
Research involving
Sponsors and support
Intervention
Outcome measures
Primary outcome
The main study parameter is self-reported itch in response to histamine
iontophoresis.
Secondary outcome
Secondary study parameters include expectations, self-reported and physical
skin condition, and wellbeing (e.g., anxiety). In addition, effects of
personality factors on expectation induction and study outcomes will be
explored. Effects on response time on the Stroop test and Trail Making Test
will be explored as well.
Background summary
There is evidence indicating that negative and positive outcome expectations
can be induced by respectively providing negative or positive information
regarding a certain (inert) treatment method, and that these expectations in
turn may influence itch sensations (i.e. nocebo and placebo effects).
Additionally, although most studies on placebo effects do not inform
participants about receiving an inert substance or treatment a priori
(closed-label placebo), there is a growing body of literature that suggests
that these effects can also occur when it is known that a given substance is
inert (open-label placebo). However, very little is known about open-label
nocebo induction. In addition, few studies have investigated the efficacy of
open-label placebo induction by verbal suggestions in itch specifically, nor
how these effects compare to closed-label placebo induction.
Study objective
The study objective is to assess whether negative and positive outcome
expectations, induced by verbal suggestions under both open- and closed-label
conditions, can influence itch during a short-term validated histamine test.
Additionally, we explore the effects of suggestions on self-reported and
physical skin response, and wellbeing. Furthermore, the influence of
personality factors on expectation induction and study outcomes will be
explored.
Study design
A randomized, controlled, within-between study design will be applied.
Participants will be randomly assigned to 1) the closed-label negative verbal
suggestions group, 2) the open-label negative verbal suggestions group, 3) the
closed-label positive verbal suggestions group, or 4) the open-label positive
verbal suggestions group. Participants will be invited for a single laboratory
session. During the session, they will receive verbal suggestions regarding a
sham transdermal patch. All participants will be told, as a cover story, that
the patch contains a substance that has a positive effect on cognitive
abilities, such as attention and processing speed of the brain. Next, they are
told that the patch, as a side effect, has either a positive or negative effect
(depending on group allocation) on the sensitivity of their skin to physical
sensations such as itch. In addition, participants in the open-label conditions
receive information regarding the role of expectations in eliciting these
effects. During the session, participants are exposed to transdermal histamine
iontophoresis twice (once for a baseline measurement, once as a measurement
following verbal suggestions), both times followed by a cognitive test (i.e.,
Stroop test, Trail Making Test). Self-reported itch will be assessed prior to,
during, and following histamine iontophoresis. Following iontophoresis,
self-reported and physical skin response (i.e., wheal, flare response) are
assessed as well. Wellbeing and expectations will be assessed several times
during the session. Participants are asked to fill in additional demographic
and personality questionnaires at the start of the session.
Intervention
Positive outcome expectations will be induced by verbal suggestions in the
open- and closed-label positive verbal suggestions groups. Negative outcome
expectations will be induced in the open- and closed-label negative verbal
suggestions groups. When suggestions are given under open-label conditions,
participants will receive additional information regarding the effects of
expectations and verbal suggestions on itch, whereas participants in the groups
under closed-label conditions do not receive this information.
Study burden and risks
Participants need to invest approximately 2 hours in the study. Given the
healthy study population, no adverse side effects are expected. The symptoms of
transdermal histamine iontophoresis (local swelling, itch, and flare) will
disappear within several minutes to a maximum of 2 hours. All other
measurements are considered minimally invasive. Participants will receive a
reimbursement of 20 euros for participation in the study.
Wassenaarseweg 52
Leiden 2333 AK
NL
Wassenaarseweg 52
Leiden 2333 AK
NL
Listed location countries
Age
Inclusion criteria
Between 18 and 35 years old; good understanding of written and spoken Dutch
Exclusion criteria
Refusal to give written informed consent; severe somatic or psychological morbidity (e.g., heart and lung diseases or DSM-IV psychiatric disorders) that would adversely affect participant*s safety or that might interfere with the study protocol; current chronic itch or pain complaints; current use of analgesics, anti-inflammatory drugs, antihistamines, or antibiotics; recent vaccinations; pregnancy; colour blindness
Design
Recruitment
Followed up by the following (possibly more current) registration
No registrations found.
Other (possibly less up-to-date) registrations in this register
In other registers
| Register | ID |
|---|---|
| CCMO | NL64502.058.17 |
| OMON | NL-OMON27413 |