Placebo and nocebo effects for itch and itch-related immune outcomes: A systematic review of animal and human studies

Stefanie H Meeuwis; Henriët van Middendorp; Antoinette I M van Laarhoven; Cora van Leijenhorst; Gustavo Pacheco-Lopez; Adriana P M Lavrijsen; Dieuwke S Veldhuijzen; Andrea W M Evers

doi:10.1016/j.neubiorev.2020.03.025

Placebo and nocebo effects for itch and itch-related immune outcomes: A systematic review of animal and human studies

Neurosci Biobehav Rev. 2020 Jun:113:325-337. doi: 10.1016/j.neubiorev.2020.03.025. Epub 2020 Mar 30.

Authors

Stefanie H Meeuwis¹, Henriët van Middendorp², Antoinette I M van Laarhoven³, Cora van Leijenhorst⁴, Gustavo Pacheco-Lopez⁵, Adriana P M Lavrijsen⁶, Dieuwke S Veldhuijzen², Andrea W M Evers³

Affiliations

¹ Health, Medical and Neuropsychology Unit, Institute of Psychology, Faculty of Social and Behavioral Sciences, Leiden University, P.O. Box 9555, 2300RB, Leiden, the Netherlands; Leiden Institute for Brain and Cognition, P.O. Box 9600, 2300RC, Leiden University Medical Center, Leiden, the Netherlands. Electronic address: s.h.meeuwis@fsw.leidenuniv.nl.
² Health, Medical and Neuropsychology Unit, Institute of Psychology, Faculty of Social and Behavioral Sciences, Leiden University, P.O. Box 9555, 2300RB, Leiden, the Netherlands; Leiden Institute for Brain and Cognition, P.O. Box 9600, 2300RC, Leiden University Medical Center, Leiden, the Netherlands.
³ Health, Medical and Neuropsychology Unit, Institute of Psychology, Faculty of Social and Behavioral Sciences, Leiden University, P.O. Box 9555, 2300RB, Leiden, the Netherlands; Leiden Institute for Brain and Cognition, P.O. Box 9600, 2300RC, Leiden University Medical Center, Leiden, the Netherlands; Department of Psychiatry, Leiden University Medical Center, P.O. Box 9600, 2300RC, Leiden, the Netherlands.
⁴ Health, Medical and Neuropsychology Unit, Institute of Psychology, Faculty of Social and Behavioral Sciences, Leiden University, P.O. Box 9555, 2300RB, Leiden, the Netherlands.
⁵ Health, Medical and Neuropsychology Unit, Institute of Psychology, Faculty of Social and Behavioral Sciences, Leiden University, P.O. Box 9555, 2300RB, Leiden, the Netherlands; Metropolitan Autonomous University (UAM), Campus Lerma, Health Sciences Department, Lerma, 52005, Edo Mex, Mexico.
⁶ Department of Dermatology, Leiden University Medical Center, P.O. Box 9600, 2300RC, Leiden, the Netherlands.

PMID: 32240668
DOI: 10.1016/j.neubiorev.2020.03.025

Abstract

Placebo and nocebo effects can influence somatic symptoms such as pain. For itch and other dermatological symptoms these effects have been far less investigated. This review systematically integrates evidence from both animal (mainly rodents) and human trials on placebo and nocebo effects in itch, itch-related symptoms and conditions of the skin and mucous membranes, and related immune outcomes (e.g., histamine). Thirty-one animal studies, and fifty-five human studies (k = 21 healthy participants, k = 34 patients) were included. Overall, studies consistently show that placebo and nocebo effects can be induced by various methods (e.g., suggestions, conditioning and social cues), despite high heterogeneity across studies. Effects of suggestions were found consistently across subjective and behavioral parameters (e.g., itch and scratching in humans), whereas conditioning was likely to impact physiological parameters under certain conditions (e.g., conditioning of histamine levels in stressed rodents). Brain areas responsible for itch processing were associated with nocebo effects. Future research may investigate how variations in methods impact placebo and nocebo effects, and whether all symptoms and conditions can be influenced equally.

Keywords: Conditioning; Dermatology; Expectancy; Itch; Nocebo effects; Placebo effects.

Publication types

Research Support, Non-U.S. Gov't
Review
Systematic Review

MeSH terms

Animals
Cues
Humans
Nocebo Effect*
Pain
Placebo Effect
Pruritus*
Suggestion