This study investigated for the first time the effects of individual and combined application of 3 learning techniques (verbal suggestions, classical conditioning, and observational learning) on... Show moreThis study investigated for the first time the effects of individual and combined application of 3 learning techniques (verbal suggestions, classical conditioning, and observational learning) on placebo analgesia and extinction.Healthy participants (N = 206) were assigned to 8 different groups in which they were taught through either a verbal suggestion, a conditioning paradigm, a video observing someone, or any combination thereof that a placebo device (inactive transcutaneous electric nerve stimulation [TENS]) was capable of alleviating heat pain, whereas one group did not (control). Placebo analgesia was quantified as the within-group difference in experienced pain when the placebo device was (sham) 'activated' or 'inactivated' during equal pain stimuli, and compared between groups.Placebo analgesia was induced in groups with 2 or 3 learning techniques. Significantly stronger placebo analgesia was induced in the combination of all 3 learning techniques as compared to the individual learning techniques or control condition, underlining the additional contribution of 3 combined techniques. Extinction did not differ between groups. Furthermore, pain expectancies, but not state anxiety or trust, mediated placebo analgesia.Our findings emphasize the added value of combining 3 learning techniques to optimally shape expectancies that lead to placebo analgesia, which can be used in experimental and clinical settings. Perspective: This unique experimental study compared the individual versus combined effects of 3 important ways of learning (verbal suggestions, classical conditioning, and observational learning) on expectation-based pain relief. The findings indicate that placebo effects occurring in clinical practice could be optimally strengthened if healthcare providers apply these techniques in combination.(R) 2023 The Author(s). Published by Elsevier Inc. on behalf of United States Association for the Study of Pain, Inc This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Show less
The aim of the current dissertation was to explore the link between the endocrine system and placebo effects with a focus on the hormone oxytocin. Two perspectives were examined: the possibility to... Show moreThe aim of the current dissertation was to explore the link between the endocrine system and placebo effects with a focus on the hormone oxytocin. Two perspectives were examined: the possibility to elicit placebo effects in the endocrine system and influencing placebo and nocebo effects by hormones. In the first part of the dissertation possibility to induce placebo effects in the endocrine system with classical conditioning is explored. A systematic review of literature and the results of a large randomized controlled trial on classical conditioning of oxytocin are described in this part. In the second part of the dissertation we explored the possibility to influence placebo and nocebo effects with oxytocin. In this part results of two randomized controlled trials are presented. We demonstrated that there is accumulating evidence in the literature that placebo effects can be elicited in the endocrine system. Moreover, we described results of a randomized controlled trial in which we successfully conditioned oxytocin release. Finally, we showed a lack of evidence that oxytocin can influence placebo and nocebo effects. Show less
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
Placebo effects are health improvements, for example pain reduction, due to an inert treatment. These effects are typically ascribed to a person’s expectations about the beneficial outcomes of... Show morePlacebo effects are health improvements, for example pain reduction, due to an inert treatment. These effects are typically ascribed to a person’s expectations about the beneficial outcomes of the placebo. The literature and experimental research in the current dissertation shows that expectancies, and thereby placebo effects, can be induced via verbal suggestion, conditioning, and mental imagery. Especially verbal suggestions may enhance analgesic treatments for patients. We found, for the first time, that mental imagery of reduced pain can induce analgesia via its effects on pain expectancies. We also observed that people’s expectations about the effectiveness of medications depend on the route of administration and targeted symptom. These findings suggest that harnessing placebo effects by targeting expectancies is promising for enhancing standard clinical care of physical symptoms. Show less
