New insights into placebo analgesia

The Optimal Learning Cocktail for Placebo Analgesia: A Randomized Controlled Trial Comparing Individual and Combined Techniques

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 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.

Placebo effects in low back pain: A systematic review and meta-analysis of the literature

BACKGROUND AND OBJECTIVE

The current treatments of primary musculoskeletal low back pain (LBP) have a low to moderate efficacy, which might be improved by looking at the contribution of placebo effects. However, the size of true placebo effects in LBP is unknown. Therefore, a systematic review and meta-analysis were executed of randomized controlled trials investigating placebo effects in LBP.

DATABASES AND DATA TREATMENT

The study protocol was registered in the international prospective register of systematic reviews Prospero (CRD42019148745). A literature search (in PubMed, Embase, The Cochrane Library, CINAHL and PsycINFO) up to 2021 February 16th yielded 2,423 studies. Two independent reviewers assessed eligibility and risk of bias.

RESULTS

Eighteen studies were eligible for the systematic review and 5 for the meta-analysis. Fourteen of the 18 studies were clinical treatment studies, and 4 were experimental studies specifically assessing placebo effects. The clinical treatment studies provided varying evidence for placebo effects in chronic LBP but insufficient evidence for acute and subacute LBP. Most experimental studies investigating chronic LBP revealed significant placebo effects. The meta-analysis of 5 treatment studies investigating chronic LBP depicted a significant moderate effect size of placebo for pain intensity (SMD = 0.57) and disability (SMD = 0.52).

CONCLUSIONS

This review shows a significant contribution of placebo effects to chronic LBP symptom relief in clinical and experimental conditions. The meta-analysis revealed that placebo effects can influence chronic LBP intensity and disability. However, additional studies are required for more supporting evidence and evidence for placebo effects in acute or subacute LBP.

SIGNIFICANCE

This systematic review and meta-analysis provides evidence of true placebo effects in low back pain (LBP). It shows a significant contribution of placebo effects to chronic LBP symptom relief. The results highlight the importance of patient- and context-related factors in fostering treatment effects in this patient group. New studies could provide insight into the potential value of actively making use of placebo effects in clinical practice.

Nocebo hyperalgesia can be induced by classical conditioning without involvement of expectancy

Influential theoretical accounts take the position that classical conditioning can induce placebo effects through conscious expectancies. In the current study two different conditioning procedures (hidden and open) were used to separate expectancy from conditioning in order to reveal the role of expectancy in the formation of nocebo hyperalgesia. Eighty-seven healthy females were randomly assigned to three groups (hidden conditioning, open conditioning, and control). Participants were selected according to the Fear of Pain Questionnaire scores and assigned to two subgroups: high and low level of fear of pain (trait). They received electrocutaneous pain stimuli preceded by either an orange or blue color. During the conditioning phase, one color was paired with pain stimuli of moderate intensity (control stimuli) and the other color was paired with pain stimuli of high intensity (nocebo stimuli) in both hidden and open conditioning groups. Only participants in the open conditioning group were informed about this association, however just before the testing phase the expectancy of hyperalgesia induced in this way was withdrawn. In the control group, both colors were followed by control pain stimuli. During the testing phase all participants received a series of stimuli of the same intensity, regardless of the preceding color. Participants rated pain intensity, expectancy of pain intensity and fear (state). We found that nocebo hyperalgesia was induced by hidden rather than open conditioning. The hidden conditioning procedure did not produce conscious expectancies related to pain. Nocebo hyperalgesia was induced in participants with low and high fear of pain and there was no difference in the magnitude of the nocebo effect between both groups. Nocebo hyperalgesia was not predicted by the fear of upcoming painful stimuli.

Investigating the effects of tDCS on Visual Orientation Discrimination Task Performance: 'The possible influence of placebo'

The non-invasive neuromodulation technique tDCS offers the promise of a low cost tool for both research and clinical applications in psychology, psychiatry and neuroscience. However, findings regarding its efficacy are often equivocal. A key issue is that the clinical and cognitive applications studied are often complex and thus effects of tDCS are difficult to predict given its known effects on the basic underlying neurophysiology, namely alterations in cortical inhibition-excitation balance. As such, it may be beneficial to assess the effects of tDCS in tasks whose performance has a clear link to cortical inhibition-excitation balance such as the visual orientation discrimination task (ODT). In prior studies in our laboratory no practise effects were found during 2 consecutive runs of the ODT, thus in the current investigation, to examine the effects of tDCS, subjects received 10 minutes of 2mA occipital tDCS (sham, anode, cathode) between a first and second run of ODT. Surprisingly, subjects' performance significantly improved in the second run of ODT compared to the first one regardless of the tDCS stimulation type they received (anodal, cathodal, or sham-tDCS). Possible causes for such an improvement could have been due to either a generic 'placebo' effect of tDCS (as all subjects received some form of tDCS) or an increased delay period between the two runs of ODT of the current study compared to our previous work (10 minutes duration required to administer tDCS as opposed to ~2 minutes in previous studies as a 'break'). As such, we tested these two possibilities with a subsequent experiment in which subjects received 2 minutes or 10 minutes delay between the 2 runs (with no tDCS) or 10 minutes of sham-tDCS. Only sham-tDCS resulted in improved performance thus these data add to a growing literature suggesting that tDCS has powerful placebo effect that may occur even in the absence of active cortical modulation.

How Classical Conditioning Shapes Placebo Analgesia: Hidden versus Open Conditioning

Objective

To investigate the influence of expectancy of pain intensity, fear of pain (trait), and fear (state) on the effectiveness of hidden and open conditioning to produce placebo analgesia.

Methods

A total of 90 healthy female volunteers were randomly assigned to three groups (hidden conditioning, open conditioning, and control) that received electrical stimuli preceded by either orange or blue lights. One color was paired with painful stimuli (control stimuli) and the other color was paired with nonpainful stimuli (conditioned stimuli) in both the hidden and open conditioning groups. Only participants in the open conditioning group were informed about this association. In the control group, both color lights were followed by control stimuli. In the testing phase, both colored lights were followed by identical control stimuli. Participants rated pain intensity, expectancy of pain intensity, fear, and fear of pain.

Results

A significant analgesic effect was found only in the hidden conditioning group, where no explicit verbal suggestions were provided. Hidden conditioning had an effect on expectancy and fear-participants in the hidden conditioning group expected less pain and experienced less fear in relation to conditioned stimuli. Fear was the only predictor of placebo analgesia in the hidden conditioning group. Neither expectancy of pain intensity nor fear of pain predicted placebo analgesia.

Conclusions

Fear seems to be a more important factor than expectancy in producing placebo analgesia induced by hidden conditioning.

From Bench to Bedside: Converting Placebo Research into Belief Activation

Research on the placebo effect contains important elements that can be harnessed to improve clinical care. This paper proposes a new term, "Belief Activation," to describe the deliberate use of placebo effect tools by both patients and clinicians to catalyze healing. Belief Activation includes, but is not limited to, maximizing patient and practitioner expectations, classical and social conditioning, spirituality and prayer/intention, therapeutic relationship, healing environments, and minimizing the nocebo effect. This paper demonstrates ways in which Belief Activation is a form of evidence-based medicine and seeks to translate knowledge from placebo research into medical practice.

The Placebo and Nocebo Phenomena: Their Clinical Management and Impact on Treatment Outcomes

PURPOSE

This overview focuses on placebo and nocebo effects in clinical trials and routine care. Our goal was to propose strategies to improve outcomes in clinical practice, maximizing placebo effects and reducing nocebo effects, as well as managing these phenomena in clinical trials.

METHODS

A narrative literature search of PubMed was conducted (January 1980-September 2016). Systematic reviews, randomized controlled trials, observational studies, and case series that had an emphasis on placebo or nocebo effects in clinical practice were included in the qualitative synthesis. Search terms included: placebo, nocebo, clinical, clinical trial, clinical setting, placebo effect, nocebo effect, adverse effects, and treatment outcomes. This search was augmented by a manual search of the references of the key articles and the related literature.

FINDINGS

Placebo and nocebo effects are psychobiological events imputable to the therapeutic context. Placebo is defined as an inert substance that provokes perceived benefits, whereas the term nocebo is used when an inert substance causes perceived harm. Their major mechanisms are expectancy and classical conditioning. Placebo is used in several fields of medicine, as a diagnostic tool or to reduce drug dosage. Placebo/nocebo effects are difficult to disentangle from the natural course of illness or the actual effects of a new drug in a clinical trial. There are known strategies to enhance clinical results by manipulating expectations and conditioning.

IMPLICATIONS

Placebo and nocebo effects occur frequently and are clinically significant but are underrecognized in clinical practice. Physicians should be able to recognize these phenomena and master tactics on how to manage these effects to enhance the quality of clinical practice.

No Effect of 2 mA Anodal tDCS Over the M1 on Performance and Practice Effect on Grooved Pegboard Test and Trail Making Test B

Previous studies suggest that transcranial direct current stimulation (tDCS) can facilitate motor performance and learning. In this double-blind experiment, 60 healthy human subjects (29 females) were randomized into three groups (active tDCS, sham tDCS, and no-treatment control group) in order to investigate the effect of a 20 min session of 2 mA tDCS over the motor cortex contralateral to the dominant hand on practice effect and performance on the Grooved Pegboard Test (GPT) and Trail Making Test (TMT). Performance was operationalized as the time to complete the tests before, during, and after stimulation. The practice effect was termed as the difference in time to complete the tests from pretest to post-test. Data on body mass index (BMI), head circumference, sleep status, interelectrode impedance, and caffeine and nicotine use were sampled to control for the influence of individual differences on the effect of tDCS. Adverse effects were registered using a standardized form. The results indicated no effect of tDCS on performance and practice effects on the GPT and TMT. For all groups, BMI was a predictor for a practice effect on the TMT. In the active tDCS group, high caffeine intake and low impedance predicted a practice effect on the GPT for the dominant hand. The present results suggest that impedance levels in tDCS studies should be routinely reported in future studies, as it might not only provide valuable information on the efficacy of the blinding conditions and participant discomfort, but also correlate with individual differences that are relevant to the outcome of the stimulation.

Aspects of psychodynamic neuropsychiatry III: magic spells, the placebo effect, and neurobiology

Through a case study, the importance of supporting the positive transference is stressed-from both a psychological and neurobiological perspective. The article argues that the neurobiology of expectation underlies transference. This neurobiology has been investigated particularly over the past several decades in work concerning the placebo effect. By understanding the neurobiology of expectation, one gains a better understanding of the neurobiology of the transference. This enables clinical predictions-and decisions-that are informed not just by the teachings of psychology but also by the science of biology.

Placebo analgesia affects the behavioral despair tests and hormonal secretions in mice

RATIONALE

The placebo effect is a fascinating yet puzzling phenomenon, which has challenged investigators over the past 50 years. In previous studies, the investigators only focused on the placebo effect obtained within a single domain, and pain is the field in which most of the placebo research has been performed. However, recent research by our laboratory (Zhang and Luo in Psychophysiology 46:626-634, 2009; Zhang et al. 2011) showed that, in human subjects, the placebo effect can be transferred from one domain to the other, namely from pain to emotion.

OBJECTIVES

The scope of this study was to investigate whether placebo analgesia could affect the depressive behavior in mice.

MATERIALS AND METHODS

Female C57/BL6 mice were trained to associate the context cue with elevated pain tolerance via a set of procedures. Then the forced swim test and tail suspension test were used to measure the depressive-like behaviors on the test day. Plasma concentrations of adrenocorticotropic hormone (ACTH) and corticosterone were also detected.

RESULTS

Our results showed that the placebo analgesia, which was established by a set of procedures in mice, was transferable and could produce a significant antidepressant effect on depressive test. Plasma levels of corticosterone and ACTH further proved that the placebo analgesia that was established from pain-reducing training not only induced a significant placebo effect on pain, but also decreased significantly the hypothalamus-pituitary-adrenal axis (HPA) response to stress and produced a stress-alleviating effect.

CONCLUSIONS

These data show that placebo analgesia affects the behavioral despair tests and hormonal secretions in mice.

Are we drawing the right conclusions from randomised placebo-controlled trials? A post-hoc analysis of data from a randomised controlled trial

Background

Assumptions underlying placebo controlled trials include that the placebo effect impacts on all study arms equally, and that treatment effects are additional to the placebo effect. However, these assumptions have recently been challenged, and different mechanisms may potentially be operating in the placebo and treatment arms. The objective of the current study was to explore the nature of placebo versus pharmacological effects by comparing predictors of the placebo response with predictors of the treatment response in a randomised, placebo-controlled trial of a phytotherapeutic combination for the treatment of menopausal symptoms. A substantial placebo response was observed but no significant difference in efficacy between the two arms.

Methods

A post hoc analysis was conducted on data from 93 participants who completed this previously published study. Variables at baseline were investigated as potential predictors of the response on any of the endpoints of flushing, overall menopausal symptoms and depression. Focused tests were conducted using hierarchical linear regression analyses. Based on these findings, analyses were conducted for both groups separately. These findings are discussed in relation to existing literature on placebo effects.

Results

Distinct differences in predictors were observed between the placebo and active groups. A significant difference was found for study entry anxiety, and Greene Climacteric Scale (GCS) scores, on all three endpoints. Attitude to menopause was found to differ significantly between the two groups for GCS scores. Examination of the individual arms found anxiety at study entry to predict placebo response on all three outcome measures individually. In contrast, low anxiety was significantly associated with improvement in the active treatment group. None of the variables found to predict the placebo response was relevant to the treatment arm.

Conclusion

This study was a post hoc analysis of predictors of the placebo versus treatment response. Whilst this study does not explore neurobiological mechanisms, these observations are consistent with the hypotheses that 'drug' effects and placebo effects are not necessarily additive, and that mutually exclusive mechanisms may be operating in the two arms. The need for more research in the area of mechanisms and mediators of placebo versus active responses is supported.

Trial Registration

International Clinical Trials Registry ISRCTN98972974.

The importance of placebo in headache research

The best way to appreciate the efficacy of drug and behavioural therapy in the acute and prophylactic treatment of headache is to perform placebo-controlled randomized trials. In order to plan and conduct these studies in the most appropriate way, it is desirable to know which factors influence the placebo response. This paper reviews factors which influence the placebo response in clinical trials, such as expectation, blinding, route of application of drugs and age, gender and geographical distribution. Response rates of placebo in the treatment of acute headache episodes are higher than in headache prophylaxis. Invasive procedures such as injections have a higher placebo response compared with oral drugs. Variables known to influence the placebo response have to be taken into consideration to calculate properly the power of planned randomized trials.

The effects of paracetamol and parecoxib on kidney function in elderly patients undergoing orthopedic surgery

The common adverse effects of traditional nonsteroidal antiinflammatory drugs on renal function include reductions in renal blood flow, glomerular filtration rate, and sodium and potassium excretion, mainly via inhibition of renal cyclooxygenase. We designed the present study to determine the effects of IV paracetamol or parecoxib on renal function in elderly patients undergoing orthopedic surgery. Seventy-five patients (76 +/- 8 yr, mean +/- sd) undergoing hip replacement or surgery of the femoral shaft completed this randomized and placebo-controlled study. After their arrival in the postanesthesia care unit, patients received an initial dose of the study medication, paracetamol 1000 mg IV (n = 25), parecoxib 40 mg IV (n = 25), or saline IV (n = 25); subsequent doses were administered for the next 3 days. Opioids were provided as rescue medication. Blood and urine samples were collected before and after surgery, and markers of renal function were determined. During the first 2 h after the initial dose of parecoxib, creatinine clearance was slightly diminished (125 +/- 83 to 86 +/- 45 mL/min, P < 0.05), whereas no significant decrease of creatinine clearance was observed in the placebo and paracetamol groups. After all treatments, sodium and potassium excretion as well as urine albumin and alpha-1-microglobulin were transiently increased (group differences: not signicifant). In conclusion, glomerular and tubular functions were transiently affected in all patients after orthopedic surgery; however, the differences between the treatment groups were small and not clinically relevant. Further studies are warranted to determine adverse renal effects of longer-lasting therapy with these drugs, especially in patients with renal impairment or concomitant diseases.

Placebos and painkillers: is mind as real as matter?

Considerable progress has been made in our understanding of the neurobiological mechanisms of the placebo effect, and most of our knowledge originates from the field of pain and analgesia. Today, the placebo effect represents a promising model that could allow us to shed new light on mind-body interactions. The mental events induced by placebo administration can activate mechanisms that are similar to those activated by drugs, which indicates a similarity between psychosocial and pharmacodynamic effects. These new neurobiological advances are already changing our conception of how clinical trials and medical practice must be viewed and conducted.

Placebo-responsive Parkinson patients show decreased activity in single neurons of subthalamic nucleus

Placebo administration is known to affect the brain both in pain and in Parkinson disease. Here we show that placebo treatment caused reduced activity in single neurons in the subthalamic nucleus of placebo-responsive Parkinsonian patients. These changes in activity were tightly correlated with clinical improvement; no decrease in activity occurred when the clinical placebo response was absent.