Contagious itch can be evoked by observing people scratching. Verbal suggestions about to-be-received itch can influence itch intensity, as shown by placebo research, but it is unknown whether this... Show moreContagious itch can be evoked by observing people scratching. Verbal suggestions about to-be-received itch can influence itch intensity, as shown by placebo research, but it is unknown whether this extends to contagious itch. The current study aimed to replicate prior findings that listening to scratching and rubbing sounds elicits contagious itch, and to investigate whether suggestions can modulate this process. Healthy participants (n = 140) received positive or negative suggestions about itch in response to the sounds (aimed to decrease or increase expected itch, respectively), or no specific suggestions as a control. Participants listened to a number of audio fragments with scratching and rubbing sounds. The amount of expected itch as well as itch sensation after each audio fragment were measured by self-report. Suggestions had no effect on the expected itch. Both rubbing and scratching sounds significantly elicited itch in all groups. Scratching sounds induced more itch than rubbing sounds exclusively in the control group. These findings indicate that short suggestions might be not effective enough to modify the expectations of people regarding contagious itch. Furthermore, suggestions modulate contagious itch to some degree, but not in the hypothesized direction. Potential similarities and differences in the neurobiological mechanisms of contagious itch and nocebo effects are discussed. Show less
BackgroundNocebo and placebo effects, i.e., adverse or beneficial treatment effects, respectively, putatively due to expectancies can modulate pain and itch. These effects can generalize within the... Show moreBackgroundNocebo and placebo effects, i.e., adverse or beneficial treatment effects, respectively, putatively due to expectancies can modulate pain and itch. These effects can generalize within the pain or itch modality. Predicting the induction and generalization of these effects can be helpful in clinical practice. This study aims to investigate whether psychological characteristics related to the fear-avoidance model predict the induction and generalization of nocebo and placebo effects on pain and itch in young healthy participants. MethodsData from two previous experiments were analyzed. In Experiment 1, we induced nocebo and placebo effects on heat pain and tested generalization to pressure pain and to cowhage-evoked itch (n = 33 in a nocebo group, n = 32 in a placebo group). In Experiment 2, we induced nocebo effects on cowhage-evoked itch and tested generalization to mechanical itch and to mechanical touch (n = 44). Potential predictors were anxiety- and stress symptoms, attention to pain/itch, and pain/itch catastrophizing. Multiple regression analyses were performed. ResultsFor nocebo effects, none of the individual psychological characteristics significantly predicted induction of nocebo effects nor their generalization. For placebo effects, only less stress symptoms, lower attention to pain, and higher pain catastrophizing weakly predicted a stronger generalization of placebo effects from heat pain to pressure pain. ConclusionThe tested psychological characteristics may not play an important role in the induction and generalization of nocebo and placebo effects in healthy individuals. However, firm conclusions cannot be drawn with the current sample. Future studies should validate findings in larger and more diverse samples. Show less
Pain and other somatosensory sensations, such as itch, can be effectively decreased by placebo effects and increased by nocebo effects. There are indications that placebo effects on pain generalize... Show morePain and other somatosensory sensations, such as itch, can be effectively decreased by placebo effects and increased by nocebo effects. There are indications that placebo effects on pain generalize to other sensations and that nocebo effects generalize within itch modalities. However, it has not yet been investigated whether learned effects can generalize within pain stimulus modalities or from pain to itch. Our aims were to test whether placebo and nocebo effects can generalize within pain modalities, ie, from heat pain to pressure pain, and across somatosensory sensations with psychophysiological similarities, ie, from heat pain to cowhage-evoked itch. For this purpose, 65 healthy participants were randomized to either a placebo or nocebo group. All participants first underwent a conditioning and verbal suggestion procedure with heat pain stimuli. Subsequently, responses to heat pain, pressure pain, and cowhage-evoked itch stimuli were tested. Results showed altered levels of heat and pressure pain with the conditioned cue in both placebo and nocebo groups in the expected directions, but no significant difference in itch in both groups. In conclusion, placebo and nocebo effects on pain may generalize within but not across stimulus modalities. This study provides a novel perspective on the role that response generalization plays in physical symptoms. Show less
Nocebo effects, that is, negative treatment outcomes due to negative expectancies, can increase itch. Moreover, indirect evidence has shown that nocebo hyperknesis can generalize to another itch... Show moreNocebo effects, that is, negative treatment outcomes due to negative expectancies, can increase itch. Moreover, indirect evidence has shown that nocebo hyperknesis can generalize to another itch modality. Knowledge on response generalization can help to prevent and decrease negative effects. The aims of this study were to investigate (1) the efficacy of inducing nocebo effects on cowhage-evoked itch via verbal suggestions and (2) whether these effects can generalize to (2a) mechanically evoked touch and (2b) mechanically evoked itch. Forty-four healthy participants watched a video suggesting that a nocebo solution increases cowhage-evoked itch and that a control solution does not affect itch. Subsequently, cowhage, mechanical itch, and mechanical touch stimuli were applied. Nocebo effects were measured as the difference in both mean and peak of the outcomes itch and urge to scratch between nocebo and control trials. Main analyses revealed significant nocebo effects on mean and peak itch for all stimuli. For urge to scratch, a significant nocebo effect was only observed for mechanical touch (peak). As mechanical stimuli did not induce pure sensations as planned, posthoc sensitivity analyses were run for mechanical stimuli that individually induced either touch or itch at baseline. These analyses showed similar results for generalization to mechanical itch, but generalization to mechanical touch was non-significant. This study showed that merely verbal suggestion can induce nocebo effects on cowhage-evoked itch and that these effects can generalize to another itch modality. Future studies may examine how to prevent negative experiences from generalizing to subsequent encounters. Show less
Becker, J.M.; Vreijling, S.R.; Van Damme, S.; Kovacs, E.A.; Veldhuijzen, D.S.; Lavrijsen, A.P.M.; ... ; Laarhoven, A.I.M. van 2022
Placebo and nocebo effects have been shown to influence subjective symptoms such as itch. These effects can be induced by influencing outcome expectations through, for example, combining the... Show morePlacebo and nocebo effects have been shown to influence subjective symptoms such as itch. These effects can be induced by influencing outcome expectations through, for example, combining the application of an inert substance (e.g., a cream) with verbal suggestions on the anticipated effects of this substance. Interestingly, placebo effects also occur when it is known that a treatment is inert (i.e., open-label placebo). However, no study to date has examined the efficacy of negative and positive verbal suggestions under similar open-label and closed-label (i.e., concealed placebo/nocebo) conditions in itch. A randomized controlled between-subjects study design was applied in which healthy volunteers (n = 92) were randomized to 1) an open-label positive verbal suggestion group, 2) a closed-label positive verbal suggestion group, 3) an open-label negative verbal suggestion group, or 4) a closed-label negative verbal suggestion group. Verbal suggestions were made regarding the topical application of an inert substance. Itch was evoked experimentally by histamine iontophoresis at baseline and again following suggestions. Itch expectations, self-reported itch during and following iontophoresis, and skin response parameters were measured. Positive suggestions were found to result in significantly lower expected itch than were negative suggestions in both open- and closed-label conditions. No effects of the suggestions on itch during iontophoresis were found, but significantly lower itch was reported in the 4 min following iontophoresis in the (combined open- and closed-label) positive compared with negative verbal suggestion groups. In addition, a smaller increase in skin temperature was found in the positive compared with negative suggestion groups. The findings illustrate a potential role of (open- and closed-label) placebo for optimizing expectations and treatment effects for itch in clinical practice. Show less
Evers, A.W.M.; Peerdeman, K.J.; Laarhoven, A.I.M. van 2019
Itch is a commonly experienced symptom of acute and chronic dermatological and systemic conditions. Placebo and nocebo effects, positive and negative effects experienced after both real and sham... Show moreItch is a commonly experienced symptom of acute and chronic dermatological and systemic conditions. Placebo and nocebo effects, positive and negative effects experienced after both real and sham interventions, putatively due to positive or negative outcome expectancies, can have a significant impact on the experience of itch and its treatment. Experimental methods to induce and study placebo and nocebo effects on itch have been developed, utilizing various combinations of expectancy-induction methods (eg, conditioning, verbal suggestions) and short-acting itch-evoking stimuli (eg, histamine, electrical, or mechanical stimulation). The aim of this review is to describe the current research methods used to induce placebo and nocebo effects on itch, and the results of these studies. The benefits and drawbacks of different expectancy-induction methods and itch-evoking stimuli are described, and future directions for research and clinical application are discussed. Show less
