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
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
Meeuwis, S.H.; Middendorp, H. van; Pacheco-Lopez, G.; Ninaber, M.K.; Lavrijsen, A.P.M.; Wee, N. van der; ... ; Evers, A.W.M. 2019
Objective Allergic rhinitis symptoms can be reduced by behaviorally conditioning antihistamine. It is unclear whether these findings extend to histamine-induced itch or work when participants are... Show moreObjective Allergic rhinitis symptoms can be reduced by behaviorally conditioning antihistamine. It is unclear whether these findings extend to histamine-induced itch or work when participants are informed about the conditioning procedure (open-label conditioning). The current study aims to investigate the efficacy of (open-label) antipruritic behavioral conditioning for histamine-induced itch. Methods Healthy participants (n = 92; 84% female) were randomized to I) an open-label conditioned, II) closed-label conditioned, III) conditioned-not-evoked control, or IV) nonconditioned control group. A two-phase conditioning paradigm was used. During acquisition, a conditioned stimulus (CS; distinctively tasting beverage) was repeatedly paired with the H-1-antihistamine levocetirizine (groups I-III). During evocation, the CS was paired with placebo (I, II), or instead of the CS, water was paired with placebo (III). The nonconditioned control group (IV) received CS with placebo in both phases. Itch after histamine iontophoresis and physiological data (i.e., spirometry, heart rate, skin conductance) were assessed. Combined conditioned and combined control groups were first compared, and analyses were repeated for separate groups. Results Marginally lower itch was reported in the combined conditioned compared with the control groups (F(1,88) = 2.10, p = .076, eta(2)(partial) = 0.02); no differences between separate groups were found. No effects on physiological data were found, except for heart rate, which reduced significantly and consistently for control groups, and less consistently for conditioned groups (group by time interaction: F(7,80) = 2.35, p = .031, eta(2)(partial) = 0.17). Conclusion Limited support was found for the efficacy of antipruritic behavioral conditioning, regardless of whether participants were informed about the conditioning procedure. The application of open-label conditioning in patient populations should be further researched. Show less
Meeuwis, S.H.; Middendorp, H. van; Pacheco-Lopez, G.; Ninaber, M.K.; Lavrijsen, A.P.M.; Wee, N. van der; ... ; Evers, A.W.M. 2019
