In various research projects, we investigate how open-label placebo and nocebo verbal suggestions affect itch. If our understanding of open-label placebo and nocebo effects can be furthered, the generated knowledge may then be used to develop novel clinical applications and improve existing treatments for patients suffering from itch and itch-related conditions.

Background

Previous studies in, among other, irritable bowel syndrome and chronic low back pain show that patients may benefit from taking open-label placebo pills (e.g., Carvalho et al, 2016; Charlesworth et al., 2017; Kaptchuk et al., 2010). In these studies, placebo pills are provided in combination with an explanation of how placebo effects may improve somatic symptoms. Open-label placebo effects may potentially provide an opportunity to utilize placebo effects mechanisms in the clinic in an ethical and transparent manner. However, little is known about the underlying mechanisms of these open-label placebo effects, nor are the distinctive effects of communication about placebo effects (the rationale) and the placebo itself (the pill) disentangled in most studies. The aim of this research line is to unravel these mechanisms and study how various components of open-label placebo and nocebo (e.g., open positive or negative verbal suggestions) may affect itch distinctively.

Methods

We use experimental designs to investigate how open-label positive and negative verbal suggestions about various placebos (i.e., dermatologically applied sham tonic, sham transdermal patches, or no placebo) affect itch differently. We look at the effects of open-label suggestions across multiple itch-associated parameters, including itch intensity, itch expectations, physical responses to histamine (wheal, flare), and markers of physiological arousal (heart rate, skin conductance, self-rated anxiety), and compare them with the placebo and nocebo effects that are elicited with covert suggestions

• Carvalho, C., Caetano, J. M., Cunha, L., Rebouta, P., Kaptchuk, T. J., & Kirsch, I. (2016). Open-label placebo treatment in chronic low back pain: a randomized controlled trial. Pain, 157(12), 2766.
• Charlesworth, J. E., Petkovic, G., Kelley, J. M., Hunter, M., Onakpoya, I., Roberts, N., Miller, F.G. & Howick, J. (2017). Effects of placebos without deception compared with no treatment: a systematic review and meta‐analysis. Journal of Evidence‐Based Medicine, 10(2), 97-107.
• Kaptchuk, T. J., Friedlander, E., Kelley, J. M., Sanchez, M. N., Kokkotou, E., Singer, J. P., Kowalczykowski, M., Miller, F.G., Kirsch, I. & Lembo, A. J. (2010). Placebos without deception: a randomized controlled trial in irritable bowel syndrome. PloS one, 5(12), e15591.

• Meeuwis, S.H., van Middendorp, H., Veldhuijzen, D.S. & Evers, A.W.M. (2021). Associations between interindividual differences, expectations and placebo and nocebo effects in itch. Frontiers in Psychology, 12, 781521.
• Meeuwis, S.H., van Middendorp, H., Lavrijsen, A.P.M., Veldhuijzen, D.S. & Evers, A.W.M. (2021). Open- and closed-label placebo and nocebo suggestions about a sham transdermal patch: effects on itch. Psychosomatic medicine, 83(1), 33-42.
• Meeuwis, S.H., van Middendorp, H., van Laarhoven, A.I.M., Veldhuijzen, D.S., Lavrijsen, A.P.M., & Evers, A.W.M. (2019). Effects of open-and closed-label nocebo and placebo suggestions on itch and itch expectations. Frontiers in psychiatry, 10, 436.
• Meeuwis, S.H., van Middendorp, H., Veldhuijzen, D.S., van Laarhoven, A.I.M., De Houwer, J., Lavrijsen, A.P.M., & Evers, A.W.M. (2017). Placebo effects of open-label verbal suggestions on itch. Acta dermato-venereologica, 98(1-2), 268-274.

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