How placebo responses are formed: a learning perspective

Socially induced placebo analgesia: a comparison of a pre-recorded versus live face-to-face observation

BACKGROUND

Recently, it has been shown that live, face-to-face social observation induces marked placebo analgesia. Despite the phenomenal growth of video sharing platforms, the potential analgesic effects of video-based social observation are largely unknown. This study compared video-based and live social observation induced placebo analgesia and whether there was a similar relationship between analgesic responses and empathy traits for both conditions.

METHODS

Here, we compared placebo analgesia in four groups: social observation through a video (SOV group), social observation in person (SOP group), verbal suggestion alone (VS group) and a natural history group (NH group). The SOV and SOP groups underwent a placebo treatment and painful stimuli following respectively a video-based and live observation of a demonstrator showing analgesic effects when the painful stimuli were paired to a green light but not a red light. The VS group received painful stimuli after they had been verbally instructed to expect less pain after the green light. The NH group received painful stimuli, but was told nothing about the meaning of the lights. Individual pain reports and empathy traits were measured.

RESULTS

We found that video-based observation induced substantial placebo analgesic responses that were of similar magnitude to live observation. Notably, the analgesic scores were strongly correlated with empathetic concern in the live observation group but not in the video replay group.

CONCLUSIONS

These findings add evidence that placebo analgesia can be induced by social observation and that empathy interacts with these effects in a context-dependent manner.

Body-Efficacy Expectation: Assessment of Beliefs concerning Bodily Coping Capabilities with a Five-Item Scale

Background. Expectancies regarding a treatment play an important role in recovery as has been shown in placebo research. The role of expectations regarding the bodily capability to overcome illness is less investigated although in complementary and alternative medicine (CAM) such capability is the target of interventions. We introduced a new construct, body-efficacy expectation, defined as the conviction that one's body is able to deal with health-threatening factors by itself, and developed and validated a scale for its measurement. Methods. The scale was developed following expert recommendations. Using online survey data from 1054 participants an exploratory factor analysis was conducted and psychometric properties of the scale were examined (item characteristics, reliability, and validity). Results. The exploratory factor analysis yielded a one-factor solution explaining 51.96% of total variance (Cronbach's α = 0.77). One of the originally six items was removed due to poor item characteristics. Correlations with several validation measures were in line with the theoretical background of the construct. Most importantly, participants with better general health showed higher body-efficacy expectation than participants with poorer health status. Conclusions. Further studies confirming the factor structure and using clinical samples are recommended. Also, the relations with the appraisal of CAM and CAM use warrant further research.

Massage reduced severity of pain during labour: a randomised trial

QUESTION

Does massage relieve pain in the active phase of labour?

DESIGN

Randomised trial with concealed allocation, assessor blinding for some outcomes, and intention-to-treat analysis.

PARTICIPANTS

46 women pregnant at ≥ 37 weeks gestation with a single fetus, with spontaneous onset of labour, 4-5cm of cervical dilation, intact ovular membranes, and no use of medication after admission to hospital.

INTERVENTION

Experimental group participants received a 30-min lumbar massage by a physiotherapist during the active phase of labour. A physiotherapist attended control group participants for the same period but only answered questions. Both groups received routine perinatal care.

OUTCOME MEASURES

The primary outcome was pain severity measured on a 100mm visual analogue scale. Secondary outcomes included the Short Form McGill Pain Questionnaire, pain location, and time to analgesic medication use. After labour, a blinded researcher also recorded duration of labour, route of delivery, neonatal outcomes, and the participant's satisfaction with the physiotherapist during labour.

RESULTS

At the end of the intervention, pain severity was 52mm (SD 20) in the experimental group and 72mm (SD 15) in control group, which was significantly different with a mean difference of 20mm (95% CI 10 to 31). The groups did not differ significantly on the other pain-related outcome measures. Obstetric outcomes were also similar between the groups except the duration of labour, which was 6.8hr (SD 1.6) in the experimental group and 5.7hr (SD 1.5) in the control group, mean difference 1.1hr (95% CI 0.2 to 2.0). Patients in both groups were satisfied with the care provided by the physiotherapist.

CONCLUSION

Massage reduced the severity of pain in labour, despite not changing its characteristics and location.

Patients' preconceptions of acupuncture: a qualitative study exploring the decisions patients make when seeking acupuncture

Background

Like any other form of healthcare, acupuncture takes place in a particular context which can enhance or diminish treatment outcomes (i.e. can produce contextual effects). Patients’ expectations of acupuncture might be an important component of contextual effects, but we know relatively little about the origins and nature of patients’ expectations or wider preconceptions about acupuncture. Our aim was to identify the processes the underpin patients’ decisions to try acupuncture and thus begin to tease out the origins and nature of patients’ preconceptions.

Methods

One-off semi-structured interviews were conducted with a purposive, varied sample of 35 adults who had tried acupuncture for various conditions. Interviews explored people’s experiences of acupuncture treatment and techniques from framework and inductive thematic analysis were used to relate the data to the research question.

Results

We identified four distinct processes within participants’ accounts of deciding to try acupuncture: establishing a need for treatment, establishing a need for a new treatment, deciding to try acupuncture, and finding an acupuncturist. Family, friends and health care professionals played a role in these processes, providing support, advice, and increasing people’s general familiarity with acupuncture. When they came to their first acupuncture appointment, participants had hopes, concerns, and occasionally concrete expectations as to the nature of acupuncture treatment and its likely effects.

Conclusions

Existing theories of how context influences health outcomes could be expanded to better reflect the psychological components identified here, such as hope, desire, optimism and open-mindedness. Future research on the context of acupuncture should consider these elements of the pre-treatment context in addition to more established components such as expectations. There appears to be a need for accessible (i.e. well-disseminated), credible, and individualised, patient-centred materials that can allay people’s concerns about the nature of acupuncture treatment and shape realistic hopes and expectations.

Expectation and the placebo effect in inflammatory skin reactions: a randomised-controlled trial

OBJECTIVE

This study investigated the placebo effect on experimentally induced skin reactions via the manipulation of expectation.

METHODS

Fifty-eight healthy volunteers were randomised into either expectancy or control groups. All participants received a baseline administration of histamine on one arm (Time 1), then a second administration on the other arm, approximately 30 minutes later (Time 2). Prior to the second administration, the expectancy group was told that an antihistamine cream (the placebo) had been applied that would reduce their skin reaction to the histamine. Expected wheal area, actual wheal area, heart rate, and heart rate variability were measured at each time point.

RESULTS

There was a positive relationship between expected and actual wheal area at Time 1. While the expectancy group expected a smaller skin reaction on the second arm they did not experience a greater reduction in wheal area, compared to control. The expectancy group had a greater reduction in heart rate during the second skin reaction, after the manipulation of expectation (p<.05).

CONCLUSION

While wheal area was not modulated, it may be worth further investigating this possibility, with modifications to the protocol. The reduction of heart rate appears to be an expectation effect and future research could elucidate mechanisms involved. There is an indication that expectations and inflammatory skin reactions are associated. Further study might aim to clarify the direction and nature of this relationship.

Role of μ-opioid system in the formation of memory of placebo responses

The endogenous opioid system is centrally involved in short-term placebo analgesic effects, but its potential regulation of memory and learning circuits, critical for the sustainability of placebo responses, has not been explored. Here we examined the recall of analgesic effects after placebo administration as a function of its initial capacity to activate μ-opioid neurotransmission. Memories of therapeutic/adverse responses 24 hours after placebo administration were associated with differences in μ-opioid neurotransmission in the Papez circuit, VTA, amygdala and septum. These data suggests that μ-opioid neurotransmission is involved in the recall of therapeutic benefit, providing a framework to understand stimulus learning and long-term therapeutic effect associations.

The gap between results from sham-controlled trials and trials using other controls in acupuncture research-the influence of context

In chronic pain studies involving acupuncture treatments, the size of the effect between acupuncture and a sham acupuncture control is usually small. By contrast, when acupuncture is compared to an active control group (usual care or standard treatment), the size of the effect is generally moderate and clinically relevant. Factors such as treatment setting, the expectations of patient and practitioner, and the interaction between patient and practitioner differ for different treatments and may influence the study outcome. In acupuncture, these factors seem to play a role. Acupuncture research is helpful in stimulating placebo research and illuminates a variety of aspects that influence the placebo response. The influence of different types of patient-practitioner interaction and their underlying mechanisms seem to be a clinically relevant area for future research, but should be researched in less complex placebo models than sham acupuncture.

Mobilizing unused resources: using the placebo concept to enhance cognitive performance

People have significant psychological resources to improve their well-being and performance, but these resources often go unused and could be better harnessed. In the medical domain, it is well established that these resources can be mobilized under certain conditions, for example in the context of the placebo effect. Here we explored whether the placebo principle can be used to enhance cognitive performance. To do so, we employed a modified placebo induction--a bogus priming method that we told participants would unconsciously enhance their knowledge and that they should hence trust their skills in an upcoming knowledge test. Participant performance was indeed enhanced, compared to a group that did not think the priming process would improve their knowledge. The study documents the relevance of the placebo effect outside the medical and therapeutic setting.

The placebo effect: advances from different methodological approaches

There is accumulating evidence from different methodological approaches that the placebo effect is a neurobiological phenomenon. Behavioral, psychophysiological, and neuroimaging results have largely contributed to accepting the placebo response as real. A major aspect of recent and future advances in placebo research is to demonstrate linkages between behavior, brain, and bodily responses. This article provides an overview of the processes involved in the formation of placebo responses by combining research findings from behavioral, psychophysiological, and neuroimaging methods. The integration of these different methodological approaches is a key objective, motivating our scientific pursuits toward a placebo research that can inform and guide important future scientific knowledge.

Introduction to placebo effects in medicine: mechanisms and clinical implications

The field of placebo research has made considerable progress in the last years and it has become a major focus of interest. We know now that the placebo effect is a real neurobiological phenomenon and that the brain's 'inner pharmacy' is a critical determinant for the occurrence of psychobiological and behavioural changes relevant to healing processes and well-being. However, harnessing the advantages of placebo effects in healthcare is still a challenge. The first part of the theme issue summarizes and discusses the various kinds of placebo mechanisms across medical fields, thereby not only focusing on two main explanatory models-expectation and conditioning theory-but also taking into account empathy and social learning, emotion and motivation, spirituality and the healing ritual. The second part of the issue focuses on questions related to transferring knowledge from placebo research into clinical practice and discusses implications for the design and interpretation of clinical trials, for the therapeutic settings in daily patient care, and for future translational placebo research.

Harnessing the placebo effect: the need for translational research

Laboratory research recently has greatly enhanced the understanding of placebo and nocebo effects by identifying specific neuromodulators and brain areas associated with them. However, little progress has been made in translating this knowledge into improved patient care. Here, we discuss the limitations in our knowledge about placebo (and nocebo) effects and the need for translational research with the aim of guiding physicians in maximizing placebo effects and minimizing nocebo effects in their routine clinical practice. We suggest some strategies for how, when and why interventions to promote beneficial placebo responses might be administered in the clinical setting.