The biochemical bases of the placebo effect

The Roles of Endogenous Opioids in Placebo and Nocebo Effects: From Pain to Performance to Prozac

Placebo and nocebo effects have been well documented for nearly two centuries. However, research has only relatively recently begun to explicate the neurobiological underpinnings of these phenomena. Similarly, research on the broader social implications of placebo/nocebo effects, especially within healthcare delivery settings, is in a nascent stage. Biological and psychosocial outcomes of placebo/nocebo effects are of equal relevance. A common pathway for such outcomes is the endogenous opioid system. This chapter describes the history of placebo/nocebo in medicine; delineates the current state of the literature related to placebo/nocebo in relation to pain modulation; summarizes research findings related to human performance in sports and exercise; discusses the implications of placebo/nocebo effects among diverse patient populations; and describes placebo/nocebo influences in research related to psychopharmacology, including the relevance of endogenous opioids to new lines of research on antidepressant pharmacotherapies.

Placebo-To be or not to be? Are there really alternatives to placebo-controlled trials?

Recent success of established treatment has driven concerns about the ethics of using placebo-controlled trials in psychiatry. Active-controlled (superiority or non-inferiority) trials do not include a placebo-arm and thus avoid the associated ethical concerns but show disadvantages in other respects. The aim of this paper is to review the available literature and critically discuss the evidence regarding the use of placebo-controlled- versus active-controlled trials. A MEDLINE/PubMed and Google Scholar search was performed. Studies included focused on the deliberation on placebo-controlled- versus active-controlled trials. Twenty-six studies were included. The most cited benefits of placebo-controlled trials were greater scientific reliability of the results and no average impact on patients' health. Disadvantages were mainly related to withholding effective treatment and limited generalizability. The most frequent argument in favor of active-controlled trials is the lower chance of receiving ineffective medication during the trial. Downsides include larger sample sizes, higher costs and lower scientific reliability of results. Most authors agree that all trial designs are relevant to psychiatric research depending on study goals. Whatsoever, data does not support forgoing placebo-controlled trials. Expert consensus is warranted to permit drawing conclusions on the debate on the relevance of placebo-controlled trials.

Evidence for Cognitive Placebo and Nocebo Effects in Healthy Individuals

Inactive interventions can have significant effects on cognitive performance. Understanding the generation of these cognitive placebo/nocebo effects is crucial for evaluating the cognitive impacts of interventional methods, such as non-invasive brain stimulation (NIBS). We report both cognitive placebo and nocebo effects on reward-based learning performance induced using an active sham NIBS protocol, verbal suggestions and conditioning in 80 healthy participants. Whereas our placebo manipulation increased both expected and perceived cognitive performance, nocebo had a detrimental effect on both. Model-based analysis suggests manipulation-specific strategic adjustments in learning-rates: Participants in the placebo group showed stronger learning from losses and reduced behavioral noise, participants in the nocebo group showed stronger learning from gains and increased behavioral noise. We conclude that experimentally induced expectancy can impact cognitive functions of healthy adult participants. This has important implications for the use of double-blind study designs that can effectively maintain blinding in NIBS studies.

Treatment of premenstrual dysphoria with continuous versus intermittent dosing of oral contraceptives: Results of a three-arm randomized controlled trial

BACKGROUND

Although traditionally dosed combined oral contraceptives (COCs) (21 days of active pills, 7 days of inactive pills) have not been demonstrated as superior to placebo for the treatment of premenstrual dysphoria (PMD), some randomized controlled trials (RCTs) indicate that oral contraceptives administered with a shortened or eliminated hormone-free interval are superior to placebo. However, results of such trials are mixed, and no existing studies have directly compared continuous and intermittent dosing schedules of the same oral contraceptive. The present study compared placebo, intermittent dosing of oral contraceptives, and continuous dosing of contraceptives for the treatment of PMD.

METHODS

Fifty-five women with prospectively confirmed PMD completed a three-arm, RCT in which they were randomized to 3 months of placebo (n = 22), intermittent drospirenone/ethinyl estradiol dosed on a 21-7 schedule (n = 17), or continuous drospirenone/estradiol (n = 16) following a baseline assessment month.

RESULTS

All three groups demonstrated similar, robust reductions in premenstrual symptoms over time. A marked placebo response was observed.

CONCLUSIONS

The study fails to replicate a uniquely beneficial effect of continuous COC on PMD. Additional work is needed to understand the psychosocial context bolstering the placebo response in women with PMD.

Placebo response to manual therapy: something out of nothing?

The mechanisms through which manual therapy inhibits musculoskeletal pain are likely multifaceted and related to the interaction between the intervention, the patient, the practitioner, and the environment. Placebo is traditionally considered an inert intervention; however, the pain research literature suggests that placebo is an active hypoalgesic agent. Placebo response likely plays a role in all interventions for pain and we suggest that the same is true for the treatment effects associated with manual therapy. The magnitude of a placebo response may be influenced by negative mood, expectation, and conditioning. We suggest that manual therapists conceptualize placebo not only as a comparative intervention, but also as a potential active mechanism to partially account for treatment effects associated with manual therapy. We are not suggesting manual therapists include known sham or ineffective interventions in their clinical practice, but take steps to maximize placebo responses to reduce pain.

Testing communication models for relactation in an Egyptian setting

BACKGROUND

Early discontinuation of breastfeeding exposes babies to severe and fatal illnesses. The aim of this study was to identify the barriers to relactation among Egyptian women who had stopped breastfeeding and to test different interventions to support the mothers to relactate.

SUBJECTS AND METHODS

We conducted a prospective longitudinal cohort study of 200 mothers from Alexandria with babies less than 3 months of age who were not breastfeeding. They were exposed to three different types of educational models (problem solving, coaching, and cautioning) and followed up by phone calls over a period of 6 weeks.

RESULTS

Compliance with the protocol for relactation varied according to the educational model used. Only 10% succeeded in relactating. The most effective educational strategy was the problem solving (45%) and the coaching (50%). The least effective was the cautioning approach (5%). Determinants of relactation included mother's education level (100%), cup feeding with no nipples or soothers (70%), and the husband's involvement (70%).

CONCLUSIONS

We conclude that the choice of appropriate educational models is key to encouraging mothers to return to breastfeeding. This study strongly supports Step Ten of the Baby Friendly Hospital Initiative.

The effect of analgesic education on pain in patients undergoing breast surgery: within 24 hours after the operation

AIM

The goal of this study was to assess the effect of patient information about the analgesics used after breast surgery, on patient's level of pain and mobilisation ability.

BACKGROUND

Pain needs to be managed efficiently; in particular, for surgical cases, postoperative pain must be effectively controlled. Information about analgesic helped reduce the severity of pain.

DESIGN

This study was a clinical trial comparing a test group that received information about the analgesic to be used and a control group that received information as usual.

METHODS

Eighty-four patients who had a modified radical mastectomy or breast-conserving surgery were included in the study. Data were collected in a breast surgery clinic with a questionnaire, with the use of Short-form McGill-Melzack Pain Questionnaire and the Visual Analogue Scale. The test group received information about the surgical pain and the analgesics that would be used during the postoperative period.

RESULTS

The results showed that the level of pain reported by patients was similar in the test and control groups. However, the average level of postoperative pain in the test group was lower than that in the control group. The total pain reduction score for the test group, after surgery, was greater than for the control group. Following surgery, 73·8% of the test group and 50·0% of the control group achieved mobilisation within the first six hours.

CONCLUSION

Informing patients about the analgesics to be used for their care reduced pain and provided earlier mobilisation.

RELEVANCE TO CLINICAL PRACTICE

The findings of this study can provide guidance to nurses and improve analgesic control of pain management.

Spirituality: an overlooked predictor of placebo effects?

Empirical findings have identified spirituality as a potential health resource. Whereas older research has associated such effects with the social component of religion, newer conceptualizations propose that spiritual experiences and the intrapersonal effects that are facilitated by regular spiritual practice might be pivotal to understanding potential salutogenesis. Ongoing studies suggest that spiritual experiences and practices involve a variety of neural systems that may facilitate neural 'top-down' effects that are comparable if not identical to those engaged in placebo responses. As meaningfulness seems to be both a hallmark of spirituality and placebo reactions, it may be regarded as an overarching psychological concept that is important to engaging and facilitating psychophysiological mechanisms that are involved in health-related effects. Empirical evidence suggests that spirituality may under certain conditions be a predictor of placebo response and effects. Assessment of patients' spirituality and making use of various resources to accommodate patients' spiritual needs reflect our most current understanding of the physiological, psychological and socio-cultural aspects of spirituality, and may also increase the likelihood of eliciting self-healing processes. We advocate the position that a research agenda addressing responses and effects of both placebo and spirituality could therefore be (i) synergistic, (ii) valuable to each phenomenon on its own, and (iii) contributory to an extended placebo paradigm that is centred around the concept of meaningfulness.

Impact of Oral Fast Release Amantadine on Movement Performance in Patients with Parkinson's Disease

Application of oral fast release amantadine and levodopa may induce an improvement of motor symptoms in patients with Parkinson’s disease (PD). The objective of this trial was to investigate the clinical efficacy of a fast release amantadine sulfate formulation on simple and complex movement performance and putative relations to the pharmacokinetic behavior in PD patients. We challenged two cohorts of 12 PD patients, who were taken off their regular antiparkinsonian treatment for at least 12 hours, with oral 300 mg amantadine sulfate. We scored motor symptoms and performed instrumental tasks, which ask for performance of simple or complex motion series under cued conditions. Motor symptoms and performance of complex movements significantly improved in contrast to the carrying-out of simple motions. N-methyl-D-aspartic acid antagonistic and dopaminomimetic amantadine also influences altered higher predominant prefrontal cognitive functions. Therefore, performance of complex motion series improved, whereas carrying-out of simple repetitive movements is more associated to the striatal dopamine dependent basal ganglia function.

Direct switch from levodopa/benserazide or levodopa/carbidopa to levodopa/carbidopa/entacapone in Parkinson's disease patients with wearing-off: efficacy, safety and feasibility--an open-label, 6-week study

The study objective was to assess the efficacy, safety and feasibility of switching from levodopa/benserazide (LB) or levodopa/carbidopa (LC) to levodopa/carbidopa/entacapone (LCE) in Parkinson's disease (PD) patients with wearing-off. This was a multicenter, open-label, 6-week study; the primary outcome was success rate based on the patient-assessed Clinical Global Impression of Change (P-CGI-C). Secondary outcomes included investigator-assessed CGI-C (I-CGI-C), change from baseline in Unified Parkinson's Disease Rating Scale (UPDRS), motor/non-motor wearing-off symptoms and quality of life-visual analog scale (QoL-VAS). After switching to LCE, 77% of patients reported an 'improvement' (p < 0.0001 vs. patients reporting 'no change or worsening'). Significant improvements were seen in I-CGI-C, UPDRS and QoL-VAS, regardless of prior therapy. Oral levodopa dosing was increased in 28% of patients; the primary outcome remained significant when these patients were excluded. The data suggest that switching from LB/LC to LCE provided a significant benefit in PD patients with wearing-off.

Understanding the nature and mechanism of foot pain

Approximately one-quarter of the population are affected by foot pain at any given time. It is often disabling and can impair mood, behaviour, self-care ability and overall quality of life. Currently, the nature and mechanism underlying many types of foot pain is not clearly understood. Here we comprehensively review the literature on foot pain, with specific reference to its definition, prevalence, aetiology and predictors, classification, measurement and impact. We also discuss the complexities of foot pain as a sensory, emotional and psychosocial experience in the context of clinical practice, therapeutic trials and the placebo effect. A deeper understanding of foot pain is needed to identify causal pathways, classify diagnoses, quantify severity, evaluate long term implications and better target clinical intervention.

Effect of mind on brain activity: evidence from neuroimaging studies of psychotherapy and placebo effect

Mentalistic variables must be considered to reach a correct understanding of the neurophysiological basis of behavior in humans. Confusion regarding the relative importance of neurophysiological and mentalistic variables can lead to important misconceptions about causes and effects in the study of human behavior. In this article, we review neuroimaging studies of the effect of psychotherapy in patients suffering from diverse forms of psychopathology (obsessive-compulsive disorder, panic disorder, unipolar major depressive disorder, spider phobia). We also review neuroimaging studies of the placebo effect in healthy individuals (placebo analgesia, psychostimulant expectation) and patients with Parkinson's disease or unipolar major depressive disorder. Mental functions and processes involved in diverse forms of psychotherapy exert a significant influence on brain activity. With regard to the placebo effect, beliefs and expectations can markedly modulate neurophysiological and neurochemical activity in brain regions involved in perception, movement, pain and various aspects of emotion processing. The findings of the neuroimaging studies reviewed here strongly support the view that the subjective nature and the intentional content of mental processes significantly influence the various levels of brain functioning (e.g. molecular, cellular, neural circuit) and brain plasticity.

Imaging the placebo response: a neurofunctional review

An emerging literature has started to document the neuronal changes associated with the placebo phenomenon. This has altered placebo from being considered a nuisance factor in clinical research to a target of scientific investigation per se. This paper reviews the neuroimaging literature on the placebo effect, and illustrates how imaging tools can improve current understanding of brain mechanisms underlying the placebo response. Imaging studies provide evidence of specific, predictable and replicable patterns of neural changes associated with placebo administration. In general, placebo responses seem mediated by "top-down" processes dependent on frontal cortical areas that generate and maintain cognitive expectancies. Dopaminergic reward pathways may underlie these expectancies. Placebo-induced clinical benefits also involve disorder-specific neuronal responses, yielding neurofunctional or neurochemical alterations similar to those produced by pharmacological treatments.

Entacapone improves complex movement performance in patients with Parkinson’s disease

BACKGROUND

A possible strategy to prolong plasma metabolism of Levodopa/Carbidopa (LD/CD) is Entacapone addition (EN), which improves impaired motor behaviour in patients with Parkinson's disease (PD).

AIMS OF THE STUDY

Objectives were to evaluate the clinical response to an increased dopaminergic substitution with EN by clinical rating and assessment of complex motions and to investigate the change of movement in PD patients during repeat drug administration during an eight hour interval.

METHODS

We used peg insertion with a computer based device and clinical rating for assessment of motor function in 20 treated PD patients. They received LD/CD and then the same LD/CD dosage plus EN in a standardised, open label fashion.

RESULTS

Motor scores and performance of the instrumental task were significantly better and the fluctuation of movement was less intense during the LD/CD/EN condition according to the motor test outcomes.

CONCLUSION

EN supplementation improves motor symptoms and provides a more continuous movement behaviour in PD patients.

Factors associated with the prophylactic effect of placebo injections in subjects enrolled in a study of botulinum toxin for migraine

We set out to identify predictors for the prophylactic effect of placebo injections in subjects with migraine by post hoc analysis of 81 subjects with episodic migraine receiving single-blind placebo injections in a prospective trial of botulinum toxin. Possible predictors of placebo prophylaxis were compared among placebo responders (PRs) and placebo non-responders (PNRs). There were 34 PRs (42%) and 47 PNRs (58%). Male gender [odds ratio (OR) 5.83, 95% confidence interval (CI) 1.12, 30.14, P = 0.022], a history of opioid use (OR 4.44, 95% CI 1.47, 13.41, P = 0.005) and injections in the neck/shoulders (OR 2.44, 95% CI 0.93, 3.19, P = 0.033) were associated with placebo response. Of subjects with two or more of these signs, 88% were PRs compared with 31% of subjects with one or less. Male gender, opioid use and injections in the neck/shoulders are associated with placebo prophylaxis. These findings may have important implications for the design of future clinical trials and for the clinical management of migraineurs.

Mind does really matter: Evidence from neuroimaging studies of emotional self-regulation, psychotherapy, and placebo effect

This article reviews neuroimaging studies of conscious and voluntary regulation of various emotional states (sexual arousal, sadness, negative emotion). The results of these studies show that metacognition and cognitive recontextualization selectively alters the way the brain processes and reacts to emotional stimuli. Neuroimaging studies of the effect of psychotherapy in patients suffering from diverse forms of psychopathology (obsessive-compulsive disorder, panic disorder, unipolar major depressive disorder, social phobia, spider phobia, borderline personality) are also examined. The results of these studies indicate that the mental functions and processes involved in diverse forms of psychotherapy exert a significant influence on brain activity. Neuroimaging investigations of the placebo effect in healthy individuals (placebo analgesia, psychostimulant expectation) and patients with Parkinson's disease or unipolar major depressive disorder are also reviewed. The results of these investigations demonstrate that beliefs and expectations can markedly modulate neurophysiological and neurochemical activity in brain regions involved in perception, movement, pain, and various aspects of emotion processing. Collectively, the findings of the neuroimaging studies reviewed here strongly support the view that the subjective nature and the intentional content (what they are "about" from a first-person perspective) of mental processes (e.g., thoughts, feelings, beliefs, volition) significantly influence the various levels of brain functioning (e.g., molecular, cellular, neural circuit) and brain plasticity. Furthermore, these findings indicate that mentalistic variables have to be seriously taken into account to reach a correct understanding of the neural bases of behavior in humans. An attempt is made to interpret the results of these neuroimaging studies with a new theoretical framework called the Psychoneural Translation Hypothesis.

The impact of patient expectations on outcomes in four randomized controlled trials of acupuncture in patients with chronic pain

In a pooled analysis of four randomized controlled trials of acupuncture in patients with migraine, tension-type headache, chronic low back pain, and osteoarthritis of the knee we investigated the influence of expectations on clinical outcome. The 864 patients included in the analysis received either 12 sessions of acupuncture or minimal (i.e. sham) acupuncture (superficial needling of non-acupuncture points) over an 8 week period. Patients were asked at baseline whether they considered acupuncture to be an effective therapy in general and what they personally expected from the treatment. After three acupuncture sessions patients were asked how confident they were that they would benefit from the treatment strategy they were receiving. Patients were classified as responders if the respective main outcome measure improved by at least fifty percent. Both univariate and multivariate analyses adjusted for potential confounders (such as condition, intervention group, age, sex, duration of complaints, etc.) consistently showed a significant influence of attitudes and expectations on outcome. After completion of treatment, the odds ratio for response between patients considering acupuncture an effective or highly effective therapy and patients who were more sceptical was 1.67 (95% confidence interval 1.20-2.32). For personal expectations and confidence after the third session, odds ratios were 2.03 (1.26-3.26) and 2.35 (1.68-3.30), respectively. Results from the 6-month follow-up were similar. In conclusion, in our trials a significant association was shown between better improvement and higher outcome expectations.

Placebo effects in primary insomnia

Placebo effects are commonly observed in insomnia clinical trials. With the advent of longer-term trials, such effects appear to be remarkably robust and durable. In this paper we review the classic factors that are believed to contribute to placebo effects and how these factors operate in insomnia randomized clinical trials. Beyond this we suggest that the episodic nature of insomnia may interact with patient preferences for intermittent dosing in such a way as to sustain placebo effects in the long term. An appreciation of the latter phenomenon may provide increased power to detect therapeutic outcomes and may be used to potentiate clinical gains.

Parkinsonism associated with neurocysticercosis

We report two cases of brainstem cysticercotic ependymitis presenting with rigid-akinetic syndrome. There was a good response to levodopa therapy as well as cysticidal therapy with albendazole, allowing later reduction of levodopa dosage in one patient and complete withdrawal in the other.

Homeopathic remedies as placebo alternatives--verification on the example of treatment of menopause-related vegetative and emotional disturbances

With the example of treatment of menopause-related vegetative and emotional disturbances, the author verifies the effectiveness of the use of Ignatia amara containing complex homeopathic remedies (IACCHR) as an alternative to placebo. Substantial improvement in psychological and psychosomatic symptoms was observed. Climacteric complaints diminished or disappeared completely in the majority of women (95.7% by patient evaluation and 96.2% by physician evaluation). Compared to standard pharmaceuticals, IACCHR treatment was tolerated better and lower risk of side effects was observed. The results obtained in this work indicate the significant therapeutic potential of this group of treatments, which is in line with the therapeutic effect of the placebo. Nevertheless, the showing of specific effects in pharmacological tests disqualifies the investigated treatments from use in a clinical trial in place of a placebo.

Placebo: its action and place in health research today--summary and conclusions

The material presented at this conference pointed to a new dimension in the prosecution of activities that seek to relieve people of disease. While the simple instrument of the placebo may show those interested in the efficacy of physiologically active chemicals the extent to which the chemical of interest is actually active, the surprising outcome of such studies is that the placebo per se is worthy of more general study. This, when taken further, points to the ways in which mind can influence the matter of the body. Of course, mind itself is an activity of matter, so we may retain the experimental approach that has told us about the world outside ourselves to examine the world that is inside our brains. New techniques and approaches to these once intractable problems are now in train. Where they will lead us we cannot predict, but as with the emergence of all new tools, we have to adopt those ethics that will carry us forward with the expectation that we will maximise benefits and minimise harms.