Nocebo hyperalgesia induced by implicit conditioning

Exploratory study of nocebo effect in senior medical students

Background

Νocebo Effect is known to induce adverse symptoms after negative expectations which can be manifested on a physical and psychological level. As 6th year medical students often face a wide range of clinical challenges and may be prone to negative expectations or beliefs affecting their pre-clinical and clinical success, we want to investigate how they are affected by the Nocebo Effect.

Objective

To investigate whether a nocebo effect can be induced when exposing final-year students to the clinical context of their training.

Methods

We used verbal suggestions as a nocebo mechanism and by using three tools, the Illness Attitude Scales, the Symptom Checklist-90, and the State-Trait Anxiety Inventory, we examined the difference in scores on measures of psychometric parameters in 33 participants who were on their 6th year medical and attended three clinics for the first time during their education. The administrations were given before and after attending each clinic, and negative verbal suggestions were given prior to the first administration. We also measured whether the overall number of clinics, had an effect on psychometric parameters.

Results

The results revealed a significant increase in second administration overall in the three clinics in specific psychometric parameters but no statistically significant difference was observed after attending consecutive clinics.

Conclusion

Students reported the occurrence of adverse symptoms in the investigated psychometric parameters, which should be noted in order to avoid potential educational clinical failure.

The Nocebo Effect: A Review of Contemporary Experimental Research

BACKGROUND

Nocebo effect, the occurrence of adverse symptoms fallowing an inactive treatment, is much less understood than its opposite, placebo effect. This systematic review of contemporary studies exploring the nocebo effect focuses on (1) the mechanisms underlying the nocebo effect, (2) the characteristics of participants exhibiting a more intensive nocebo response, and (3) the circumstances that might reduce or prevent the nocebo effect.

METHOD

We included experimental nocebo studies published in English that examined the occurrence of nocebo in various domains (i.e., types of sensations and symptoms) and different levels of nocebo response (e.g., performance, self-assessment) and in different populations of participants (healthy and clinical). Using Web of Science, PsycInfo and PubMed, we identified 25 papers (35 studies) that met our criteria with a total of N = 2614 participants, mostly healthy volunteers.

RESULTS

Nocebo was invoked by manipulating expectations, conditioning or both. A narrative content synthesis was conducted. Nocebo was successfully invoked in a range of domains (e.g., pain, nausea, itch, skin dryness) and levels (sensory, affective, psychological, and behavioral). Various characteristics of the conditioning procedure and participants' emotions, expectations, and dispositions are found to be related to the nocebo response, which sheds insight into the possible mechanisms of the nocebo effect. Strategies successful and unsuccessful in diminishing the nocebo response are identified. Limitations of this review include a small sample of studies.

CONCLUSION

These findings point to the universality of nocebo as well as to the importance of participant characteristics and experimental circumstances in invoking the nocebo effect. Further research should examine the nocebo effect in clinical populations.

In anticipation of pain: expectancy modulates corticospinal excitability, autonomic response, and pain perception

ABSTRACT

Pain is a ubiquitous experience encompassing perceptual, autonomic, and motor responses. Expectancy is known to amplify the perceived and autonomic components of pain, but its effects on motor responses are poorly understood. Understanding expectancy modulation of corticospinal excitability has important implications regarding deployment of adaptive and maladaptive protective behaviours in anticipation of pain. We developed a protocol to compare corticospinal excitability to expected high pain, expected low pain, and critically low pain when high pain was expected. Expecting high pain suppressed corticospinal excitability and heightened perceptual and autonomic responses to the low-pain stimulus, as with increased noxious stimulation (ie, expected high pain). Multilevel modelling revealed that perceived pain mediated the effect of both noxious stimulation and this expectancy-modulated pain on autonomic responses, but corticospinal excitability did not. These results demonstrate that merely expecting pain influenced all pain components. Findings shed new light on the aetiology of expectancy-modulated pain, whereby expecting pain mobilises the motor system to protect the body from harm by a protective withdrawal reflex, associated with reduced corticospinal excitability, and activates similar processes as increased nociceptive stimulation. This has significant practical implications for the treatment of pain, particularly in scenarios where avoidance of pain-related movement contributes to its maintenance.

Behavioral and electrodermal data on implicit nocebo conditioning using supraliminally presented visual stimuli

This article contains intensity and aversiveness ratings of electrical stimuli and data on electrodermal activity (skin conductance level and skin conductance response) during an implicit conditioning procedure. Further, answers from a questionnaire on contingency awareness are provided. The experiment consisted of three phases. In the acquisition, two types of visual stimuli (CS+ and CS-) were coupled to weakly and moderately painful electrical stimuli presented to the participants’ (N = 48) dominant hand. In the test phase, after both CS+ and CS- only the weakly painful electrical stimuli were presented. In the contingency test phase, no more electrical stimuli were presented and participants had the task to rate intensity and aversiveness as if an electrical stimulus had been presented. This phase served as a test for first-order contingency awareness. Afterwards participants filled in a questionnaire with five questions to assess their level of second-order contingency awareness. For more insight, please see Nocebo hyperalgesia induced by implicit conditioning (Bräscher and Witthöft, 2019).

Placebo and Nocebo Effects Across Symptoms: From Pain to Fatigue, Dyspnea, Nausea, and Itch

Placebo and nocebo effects are, respectively, the helpful and harmful treatment effects that do not arise from active treatment components. These effects have thus far been researched most often in pain. It is not yet clear to what extent these findings from pain can be generalized to other somatic symptoms. This review investigates placebo and nocebo effects in four other highly prevalent symptoms: dyspnea, fatigue, nausea, and itch. The role of learning mechanisms (verbal suggestions, conditioning) in placebo and nocebo effects on various outcomes (self-reported, behavioral, and physiological) of these different somatic symptoms is explored. A search of experimental studies indicated that, as in pain, the combination of verbal suggestion and conditioning is generally more effective than suggestion alone for evoking placebo and nocebo effects. However, conditioning appears more and verbal suggestions less relevant in symptoms other than pain, with the exception of placebo effects on fatigue and nocebo effects on itch. Physiological measures, such as heart rate, lung function, or gastric activity, are rarely affected even when self-reported symptoms are. Neurobiological correlates are rarely investigated, and few commonalities appear across symptoms. Expectations generally predict placebo and nocebo effects for dyspnea and itch but seem less involved in fatigue and nausea. Individual characteristics do not consistently predict placebo or nocebo effects across symptoms or studies. In sum, many conclusions deriving from placebo and nocebo pain studies do appear to apply to other somatic symptoms, but a number of important differences exist. Understanding what type of learning mechanisms for which symptom are most likely to trigger placebo and nocebo effects is crucial for generalizing knowledge for research and therapies across symptoms and can help clinicians to optimize placebo effects in practice.