Understanding the Placebo Effect: Contributions from Neuroimaging

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.

Neural correlates of citalopram and placebo response in acute bipolar depression: A randomized trial

While serotonin reuptake inhibitors are sometimes used in clinical practice to treat acute bipolar depression, the neurophysiological substrates underlying their efficacy are little studied. In the context of a larger clinical efficacy trial, the present study explored neural mechanisms associated with citalopram versus placebo treatment for bipolar depression. FDG-PET imaging examined whole-brain metabolic changes before and after treatment. Clinical efficacy was similar for citalopram versus placebo. Neuroimaging results demonstrated greater glucose metabolism in the left orbitofrontal cortex (OFC) before treatment (combined citalopram and placebo subjects) relative to after treatment, but did not correlate with clinical recovery. Glucose metabolism in the left OFC was also a predictor of depression severity when baseline scans were regressed with baseline MADRS scores. Despite of our small sample size and possibly underpowered whole-brain analysis approach, these preliminary results suggest the OFC, a key region involved in reward circuity, may be a neural substrate for depressive symptom improvement in bipolar depression, regardless of whether due to active treatment or placebo.

Placebo Effects in Clinical Trials Evaluating Patients with Uncontrolled Persistent Asthma

Rationale: Patients with uncontrolled, persistent asthma can show substantial health improvements when administered placebo.Objectives: We analyzed five randomized, placebo-controlled clinical trials that assessed subjects with uncontrolled, persistent asthma to determine the magnitudes of placebo effects across different clinical outcomes.Methods: Placebo effects for objective asthma-related outcomes, healthcare utilization outcomes, and patient-reported outcomes were estimated, with adjustments for regression to the mean.Results: Statistically significant improvements in all clinical outcomes were seen in patients randomized to placebo across all trials. Placebo effects were largest for healthcare utilization outcomes, including exacerbations (median reduction, 0.44 events/yr; 31% risk reduction; range, 19-56%), emergency department visits (median reduction, 0.19 events/yr; 50% risk reduction; range, 36-82%), and hospitalizations for asthma (median reduction, 0.26 events/yr; 66% risk reduction; range, 61-74%). Patient-reported outcomes exhibited intermediate placebo effects. Median improvements in the Asthma Control Questionnaire and St. George's Respiratory Questionnaire scores in placebo-treated patients were 0.53 units (25% improvement; range, 18-30%) and 8.3 units (19.5% improvement; range 19-20%), respectively. Forced expiratory volume in 1 second exhibited the smallest relative placebo effects (median increase, 77 ml; 4.2% improvement; range, 3.4-4.9%). Subgroup analyses did not reveal patient subgroups that were more susceptible to placebo effects. Pre- and postrandomization counts for asthma exacerbations showed patterns consistent with the expected negative binomial distribution except for significant departures in prerandomization exacerbations for two trials.Conclusions: Patients with uncontrolled asthma derived consistent benefit from randomization to placebo. Observed placebo effects may represent beneficial effects of both sham therapy and a structured asthma regimen dictated by the study protocol. In the case of healthcare utilization outcomes, recall errors in self-reported healthcare events may have introduced biases that inflated placebo effect estimates.

Characterizing the Placebo Response in Adults With ADHD

Objective: Several ADHD pharmacological trials reported high placebo response (PR) rates. This study aims to characterize the PR in adult ADHD. Method: A retrospective cohort analysis of the placebo arm (140 adults with ADHD, 18-55 yrs, M:F 46.4%-53.6%) of a 6-week randomized, multicenter, double-blind metadoxine study, using Conners' Adult ADHD Rating Scale (CAARS) and the Adult ADHD Self-Report Scale (ASRS), was conducted. Results: Pre-post changes in placebo-treated adults were significant for both the CAARS and ASRS, F(2.9, 404.5) = 61.2, p < .00001, F(2.8, 383.0) = 43.1, p < .00001, respectively. Less than half of the participants had a PR which began early in treatment and persisted; almost 50% had a variable, inconsistent PR. Conclusion: In the current sample, PR in adult ADHD was prominent on both symptom scales and the investigator-rater instrument. Therefore, using investigator ratings as a primary endpoint does not necessarily attenuate PR. Of note, about half of the PR is variable, suggesting unreliable determination of efficacy.

Neural Predictors of the Antidepressant Placebo Response

The antidepressant placebo response remains a barrier to the development of novel therapies for depression, despite decades of efforts to identify and methodologically address its clinical correlates. This manuscript reviews recent neuroimaging studies that aim to identify the neural signature of antidepressant placebo response. Data captured in clinical trials have primarily focused on antidepressant efficacy or predicting antidepressant response and have reliably implicated the rostral anterior cingulate cortex (rACC) in antidepressant placebo response, but also in medication response. Imaging and electroencephalography (EEG) experiments specifically interrogating the mechanism of antidepressant placebo response, while few, suggest the reward network, including opiate neurotransmission, is also involved. Therefore, while the rACC is likely involved in the antidepressant placebo response, its observation in isolation is unlikely to prospectively distinguish antidepressant placebo from medication responders. Instead, future studies of antidepressant placebo response should probe the reward network as a whole and incorporate sophisticated computational analytical approaches.

Medical anthropology and symbolic cure: from the placebo to cultures of meaningful healing

The perspectives of medical anthropology on symbolic cure are crucial for understanding placebo mechanisms on the medical agenda. However, while classic biomedical conceptions of the placebo discredited cultural factors as legitimate therapeutic tools, the anthropological critical approach confronted this perspective in the opposite way, rejecting the role of neurobiological factors, and using culture as a self-contained phenomenon. This manuscript is a review of the symbolic healing, stressing the importance of an integrated and interdisciplinary study of the placebo response, and the need to go beyond both biological and cultural reductionisms. Various perspectives from medical anthropology will be described, ranging from classical to multilevel perspectives that enable consideration of the placebo in its neurobiological, psychological and cultural dimensions.

Correlation of Pain Reduction with fMRI BOLD Response in Osteoarthritis Patients Treated with Paracetamol: Randomized, Double-Blind, Crossover Clinical Efficacy Study

Objective

To assess the relationship between the analgesic efficacy of extended-release paracetamol (ER-APAP) and brain blood oxygen level–dependent (BOLD) signal activation in response to painful stimulation measured by functional magnetic resonance imaging (fMRI) in patients with osteoarthritis of the knee.

Methods

This placebo-controlled, double-blind, crossover, randomized trial (N = 25) comprised three treatment periods in which patients received four doses of an eight-hour ER-APAP caplet (2 x 665 mg), four doses of matched placebo, and no treatment. Pain intensity of the knee was measured before and after painful stimulation at the knee with osteoarthritis and before and after fMRI.

Results

ER-APAP significantly reduced prestimulation osteoarthritis knee joint pain compared with baseline (P < 0.003) and placebo (P < 0.004). ER-APAP and placebo significantly reduced knee joint pain after stimulation (P = 0.014 and P = 0.032, respectively); however, pain reduction with ER-APAP was 35% greater than placebo. ER-APAP was associated with significant reductions in BOLD signal activation after stimulation compared with control in the sensory cortex (P = 0.002) and supramarginal gyrus (P = 0.003). Reduction in BOLD signal activation after stimulation for placebo was significantly greater than control in the subgenual prefrontal cortex (P < 0.001), frontal cortex (P < 0.001), insula (P < 0.003), and sensory cortex (P < 0.001).

Conclusions

ER-APAP had a significantly greater effect than placebo and no treatment in reducing knee pain, which was associated with reduced BOLD signal activations in pain pathways, including the sensory cortex and supramarginal gyrus. BOLD observations after placebo treatment may shed light on the role of the brain regions potentially involved in placebo response in clinical trials investigating pain therapies.

Immediate Effects of Spinal Manipulation on Shoulder Motion Range and Pain in Individuals With Shoulder Pain: A Randomized Trial

OBJECTIVE

The purpose of this study was to investigate the influence of thoracic spinal manipulation (SM) on shoulder pain and ranges of motion in individuals with shoulder pain.

METHODS

The sample was composed of 60 individuals, randomly allocated into the manipulation group (n = 30), who received the SM, and the placebo group (n = 30) who received a placebo manipulation. Pain evaluation was performed using the visual analog scale, and evaluation of shoulder flexion and abduction ranges of motion was assessed using a goniometer pre- and post-intervention. The intervention was performed by either upper thoracic SM or a placebo manipulation.

RESULTS

The manipulation group demonstrated increased flexion and abduction of the painful shoulder (P < .01) and increased abduction of the nonpainful shoulder (P = .03), but only the abduction of the painful shoulder reached the minimal detectable change. The placebo group showed a post-intervention increase in the flexion (P = .03) and abduction (P < .01) movement of the painful shoulder. Both groups presented a statistically significant reduction in post-intervention pain (P < .01), but not clinically significant.

CONCLUSION

Although the SM demonstrated a statistically significant difference for shoulder pain, this was not over the clinically meaningful change. Only the abduction of the painful shoulder reached the minimal detectable change.

A Context-Based Analgesia Model in Rats: Involvement of Prefrontal Cortex

Cognition and pain share common neural substrates and interact reciprocally: chronic pain compromises cognitive performance, whereas cognitive processes modulate pain perception. In the present study, we established a non-drug-dependent rat model of context-based analgesia, where two different contexts (dark and bright) were matched with a high (52°C) or low (48°C) temperature in the hot-plate test during training. Before and after training, we set the temperature to the high level in both contexts. Rats showed longer paw licking latencies in trials with the context originally matched to a low temperature than those to a high temperature, indicating successful establishment of a context-based analgesic effect in rats. This effect was blocked by intraperitoneal injection of naloxone (an opioid receptor antagonist) before the probe. The context-based analgesic effect also disappeared after optogenetic activation or inhibition of the bilateral infralimbic or prelimbic sub-region of the prefrontal cortex. In brief, we established a context-based, non-drug dependent, placebo-like analgesia model in the rat. This model provides a new and useful tool for investigating the cognitive modulation of pain.

Role of the Prefrontal Cortex in Pain Processing

The prefrontal cortex (PFC) is not only important in executive functions, but also pain processing. The latter is dependent on its connections to other areas of the cerebral neocortex, hippocampus, periaqueductal gray (PAG), thalamus, amygdala, and basal nuclei. Changes in neurotransmitters, gene expression, glial cells, and neuroinflammation occur in the PFC during acute and chronic pain, that result in alterations to its structure, activity, and connectivity. The medial PFC (mPFC) could serve dual, opposing roles in pain: (1) it mediates antinociceptive effects, due to its connections with other cortical areas, and as the main source of cortical afferents to the PAG for modulation of pain. This is a ‘loop’ where, on one side, a sensory stimulus is transformed into a perceptual signal through high brain processing activity, and perceptual activity is then utilized to control the flow of afferent sensory stimuli at their entrance (dorsal horn) to the CNS. (2) It could induce pain chronification via its corticostriatal projection, possibly depending on the level of dopamine receptor activation (or lack of) in the ventral tegmental area-nucleus accumbens reward pathway. The PFC is involved in biopsychosocial pain management. This includes repetitive transcranial magnetic stimulation, transcranial direct current stimulation, antidepressants, acupuncture, cognitive behavioral therapy, mindfulness, music, exercise, partner support, empathy, meditation, and prayer. Studies demonstrate the role of the PFC during placebo analgesia, and in establishing links between pain and depression, anxiety, and loss of cognition. In particular, losses in PFC grey matter are often reversible after successful treatment of chronic pain.

Phantom Acupuncture Induces Placebo Credibility and Vicarious Sensations: A Parallel fMRI Study of Low Back Pain Patients

Although acupuncture is an effective therapeutic intervention for pain reduction, the exact difference between real and sham acupuncture has not been clearly understood because a somatosensory tactile component is commonly included in the existing sham acupuncture protocols. In an event-related fMRI experiment, we implemented a novel form of sham acupuncture, phantom acupuncture, that reproduces the acupuncture needling procedure without somatosensory tactile stimulation while maintaining the credibility of the acupuncture treatment context. Fifty-six non-specific low back pain patients received either real (REAL) or phantom (PHNT) acupuncture stimulation in a parallel group study. The REAL group exhibited greater activation in the posterior insula and anterior cingulate cortex, reflecting the needling-specific components of acupuncture. We demonstrated that PHNT could be delivered credibly. Interestingly, the PHNT-credible group exhibited bilateral activation in SI/SII and also reported vicarious acupuncture sensations without needling stimulation. The PHNT group showed greater activation in the bilateral dorsolateral/ventrolateral prefrontal cortex (dlPFC/vlPFC). Moreover, the PHNT group exhibited significant pain reduction, with a significant correlation between the subjective fMRI signal in the right dlPFC/vlPFC and a score assessing belief in acupuncture effectiveness. These results support an expectation-related placebo analgesic effect on subjective pain intensity ratings, possibly mediated by right prefrontal cortex activity.

Use of Integrative Medicine in the United States Military Health System

Integrative medicine (IM) is a model of care which uses both conventional and nonconventional therapies in a "whole person" approach to achieve optimum mental, physical, emotional, spiritual, and environmental health, and is increasingly popular among patients and providers seeking to relieve chronic or multifactorial conditions. The US Department of Defense (DoD) shows particular interest in and usage of IM for managing chronic conditions including the signature "polytrauma triad" of chronic pain, traumatic brain injury (TBI), and posttraumatic stress disorder (PTSD) among its beneficiaries in the Military Health System (MHS). These modalities range from conventional nondrug, nonsurgical options such as cognitive-behavioral therapy to nonconventional options such as acupuncture, chiropractic, and mind-body techniques. These are of particular interest for their potential to relieve symptoms without relying on opiates, which impair performance and show high potential for abuse while often failing to provide full relief. This review describes the use of IM in the MHS, including definitions of the model, common therapies and potential for use, and controversy surrounding the practice. More research is needed to build a comprehensive usage analysis, which in turn will inform sound clinical and financial practice for the MHS and its beneficiaries.

Active pain coping is associated with the response in real-time fMRI neurofeedback during pain

Real-time functional magnetic resonance imaging (rt-fMRI) neurofeedback is used as a tool to gain voluntary control of activity in various brain regions. Little emphasis has been put on the influence of cognitive and personality traits on neurofeedback efficacy and baseline activity. Here, we assessed the effect of individual pain coping on rt-fMRI neurofeedback during heat-induced pain. Twenty-eight healthy subjects completed the Coping Strategies Questionnaire (CSQ) prior to scanning. The first part of the fMRI experiment identified target regions using painful heat stimulation. Then, subjects were asked to down-regulate the pain target brain region during four neurofeedback runs with painful heat stimulation. Functional MRI analysis included correlation analysis between fMRI activation and pain ratings as well as CSQ ratings. At the behavioral level, the active pain coping (first principal component of CSQ) was correlated with pain ratings during neurofeedback. Concerning neuroimaging, pain sensitive regions were negatively correlated with pain coping. During neurofeedback, the pain coping was positively correlated with activation in the anterior cingulate cortex, prefrontal cortex, hippocampus and visual cortex. Thermode temperature was negatively correlated with anterior insula and dorsolateral prefrontal cortex activation. In conclusion, self-reported pain coping mechanisms and pain sensitivity are a source of variance during rt-fMRI neurofeedback possibly explaining variations in regulation success. In particular, active coping seems to be associated with successful pain regulation.

The power and value of placebo and nocebo in painful osteoarthritis

This paper reviews some recent advances in our understanding of the effects of sham or dummy interventions on pain and other symptoms in osteoarthritis (OA), and outlines two new approaches to the investigation of placebo and nocebo effects. We argue that the placebo effect provides us with a valuable way of investigating the nature of conditions like OA. For example, by examining which symptoms, biochemical markers or imaging features do or do not respond to placebo, we might learn more about the relationships between pathology and symptoms in OA. Placebo and nocebo effects are positive or negative outcomes resulting from the human interactions and contexts in which healthcare consultations take place. Subtle changes in behaviours and the environments in which consultations take place can have major effects on pain and other symptoms being experienced by people with OA. Nocebo effects are particularly powerful, leading to many health-care professionals (HCPs) causing unintended harm to their clients. Based on our own research, we conclude that beneficial outcomes are most likely to occur when both the (HCP) and the client feel safe and relaxed, and when the experiences of the client are validated by the (HCP). These findings have important implications for clinical practice. We believe that research in this field needs to be 'trans-disciplinary', escaping from the constraints of the purely biomedical, deterministic, positivist paradigm of most medical research. We provide the example of our own work which combines performance studies and scholarship, with psychology and medicine.

Varenicline-Induced Elevation of Dopamine in Smokers: A Preliminary [(11)C]-(+)-PHNO PET Study

Varenicline, a nicotinic partial agonist, is the most effective treatment for tobacco use disorder. However, its mechanism of action is still unclear and may involve stimulating dopaminergic transmission. Here we used PET imaging with [(11)C]-(+)-PHNO to explore for the first time the impact of varenicline on dopamine transmission in the D2-rich striatum and D3-rich extra-striatal regions and its relationship with craving, withdrawal and smoking. Eleven treatment-seeking smokers underwent two PET scans with [(11)C]-(+)-PHNO, each following 12-h overnight smoking abstinence both prior to receiving varenicline and following 10-11 days of varenicline treatment (ie, at steady-state drug levels). Subjective measures of craving and urges to smoke were also assessed on the days of the PET scans. Varenicline treatment significantly reduced [(11)C]-(+)-PHNO binding in the dorsal caudate (p=0.008) and reduced some craving measures. These findings provide the first evidence that varenicline is able to increase DA levels in the human brain, a factor that may contribute to its therapeutic efficacy.

Mechanisms of the placebo effect in pain and psychiatric disorders

Placebo effect research over the past 15 years has improved our understanding of how placebo treatments reduce patient symptoms. The expectation of symptom improvement is the primary factor underlying the placebo effect. Such expectations are shaped by past experiences, contextual cues and biological traits, which ultimately modulate one's degree of response to a placebo. The body of evidence that describes the physiology of the placebo effect has been derived from mechanistic studies primarily restricted to the setting of pain. Imaging findings support the role of endogenous opioid and dopaminergic networks in placebo analgesia in both healthy patients as well as patients with painful medical conditions. In patients with psychiatric illnesses such as anxiety disorders or depression, a vast overlap in neurological changes is observed in drug responders and placebo responders supporting the role of serotonergic networks in placebo response. Molecular techniques have been relatively underutilized in understanding the placebo effect until recently. We present an overview of the placebo responder phenotypes and genetic markers that have been associated with the placebo effect in pain, schizophrenia, anxiety disorders and depression.

Placebo and nocebo effects: a complex interplay between psychological factors and neurochemical networks

Placebo and nocebo effects have recently emerged as an interesting model to understand some of the intricate underpinnings of the mind-body interaction. A variety of psychological mechanisms, such as expectation, conditioning, anxiety modulation, and reward, have been identified, and a number of neurochemical networks have been characterized across different conditions, such as pain and motor disorders. What has emerged from the recent insights into the neurobiology of placebo and nocebo effects is that the psychosocial context around the patient and the therapy, which represents the ritual of the therapeutic act, may change the biochemistry and the neuronal circuitry of the patient's brain. Furthermore, the mechanisms activated by placebos and nocebos have been found to be the same as those activated by drugs, which suggests a cognitive/affective interference with drug action. Overall, these findings highlight the important role of therapeutic rituals in the overall therapeutic outcome, including hypnosis, which may have profound implications both in routine medical practice and in the clinical trials setting.

Placebo analgesia and reward processing: integrating genetics, personality, and intrinsic brain activity

Our expectations about an event can strongly shape our subjective evaluation and actual experience of events. This ability, applied to the modulation of pain, has the potential to affect therapeutic analgesia substantially and constitutes a foundation for non-pharmacological pain relief. A typical example of such modulation is the placebo effect. Studies indicate that placebo may be regarded as a reward, and brain activity in the reward system is involved in this modulation process. In the present study, we combined resting-state functional magnetic resonance imaging (rs-fMRI) measures, genotype at a functional COMT polymorphism (Val158Met), and personality measures in a model to predict the magnitude of placebo conditioning effect indicated by subjective pain rating reduction to calibrated noxious stimuli. We found that the regional homogeneity (ReHo), an index of local neural coherence, in the ventral striatum, was significantly associated with conditioning effects on pain rating changes. We also found that the number of Met alleles at the COMT polymorphism was linearly correlated to the suppression of pain. In a fitted regression model, we found the ReHo in the ventral striatum, COMT genotype, and Openness scores accounted for 59% of the variance in the change in pain ratings. The model was further tested using a separate data set from the same study. Our findings demonstrate the potential of combining resting-state connectivity, genetic information, and personality to predict placebo effect.

Great expectations: the placebo effect in Parkinson's disease

Our understanding of the neural mechanisms underlying the placebo effect has increased exponentially in parallel with the advances in brain imaging. This is of particular importance in the field of Parkinson's disease, where clinicians have described placebo effects in their patients for decades. Significant placebo effects have been observed in clinical trials for medications as well as more invasive surgical trials including deep-brain stimulation and stem-cell implantation. In addition to placebo effects occurring as a byproduct of randomized controlled trials, investigation of the placebo effect itself in the laboratory setting has further shown the capacity for strong placebo effects within this patient population. Neuroimaging studies have demonstrated that placebos stimulate the release of dopamine in the striatum of patients with Parkinson's disease and can alter the activity of dopamine neurons using single-cell recording. When taken together with the findings from other medical conditions discussed elsewhere in this publication, a unified mechanism for the placebo effect in Parkinson's disease is emerging that blends expectation-induced neurochemical changes and disease-specific nigrostriatal dopamine release.

Mechanisms and therapeutic implications of the placebo effect in neurological and psychiatric conditions

The power of a placebo to effect clinically meaningful neurobiological change comparable to pharmacological therapies has been demonstrated, although the mechanisms are not fully understood. Predicting placebo responsiveness has only recently received more attention, but psychological disposition, contextual and biological factors are now known to dramatically affect a person's susceptibility to the placebo effect. The placebo effect depends upon expectancies that can be modified in a number of ways, including conditioning through explicit or implicit learned associations. Based on the dopaminergic response to anticipation of benefit in Parkinson's disease, it was suggested that the placebo effect can be seen as analogous to the expectation of reward. Dopaminergic pathways have since been implicated in the placebo response in pain and depression. Additionally, endogenous opioid release is known to mediate many forms of placebo analgesia. We provide an overview of the mechanisms and the therapeutic implications of the placebo effect in neurological and psychiatric conditions. We include evidence for detrimental effects arising from seemingly inert interventions, termed the 'nocebo effect.' Neuroimaging has critically advanced the study of the placebo effect and provides some of the strongest evidence for the mechanisms of this phenomenon prevalent across an array of human health-related circumstances. This review specifically focuses on mechanisms of the placebo effect in the three conditions that have most significantly demonstrated this effect and for which a plausible physiological basis can be identified: pain, PD and depression. Other neurological and psychiatric diseases reviewed include multiple sclerosis, Huntington's disease, Alzheimer's disease, schizophrenia and epilepsy.

Decision-making using fMRI in clinical drug development: revisiting NK-1 receptor antagonists for pain

Substance P (SP) and neurokinin-1 receptors (NK-1R) are localized within central and peripheral sensory pain pathways. The roles of SP and NK-1R in pain processing, the anatomical distribution of NK-1R and efficacy observed in preclinical pain studies involving pain and sensory sensitization models, suggested that NK-1R antagonists (NK-1RAs) would relieve pain in patient populations. Despite positive data available in preclinical tests for a role of NK-1RAs in pain, clinical studies across several pain conditions have been negative. In this review, we discuss how functional imaging-derived information on activity in pain-processing brain regions could have predicted that NK-1RAs would have a low probability of success in this therapeutic domain.

Placebo-induced improvements: how therapeutic rituals affect the patient's brain

The placebo effect has evolved from being thought of as a nuisance in clinical research to a biological phenomenon worthy of scientific investigation. The study of the placebo effect and of its evil twin, the nocebo effect, is basically the study of the therapeutic ritual around the patient, and it plays a crucial role in the therapeutic outcome. In recent years, different types of placebo responses have been analyzed with sophisticated biological tools that have uncovered specific mechanisms at the neuroanatomical, neurophysiological, biochemical, and cellular levels. Most of our knowledge about the neurobiological mechanisms of the placebo response comes from pain and Parkinson's disease, whereby the neuronal networks involved in placebo responsiveness have been identified. In the first case, opioid, cannabinoid, and cholecystokinin circuits have been found to be involved. In the second case, dopaminergic activation in the striatum and neuronal changes in basal ganglia have been described. This recent research has revealed that these placebo-induced biochemical and cellular changes in a patient's brain are very similar to those induced by drugs. This new way of thinking may have profound implications in clinical trials and medical practice both for pharmacological interventions and for nonpharmacological treatments such as acupuncture.

The placebo response: how words and rituals change the patient's brain

OBJECTIVE

The placebo effect, or response, has evolved from being thought of as a nuisance in clinical and pharmacological research to a biological phenomenon worthy of scientific investigation in its own right. The study of the placebo effect and of its negative counterpart, the nocebo effect, is basically the study of the psychosocial context around the treatment and the patient, and it plays a crucial role in the therapeutic outcome.

METHODS

In recent years, different types of placebo responses have been analyzed with sophisticated biological tools that have uncovered specific mechanisms at the anatomical, physiological, biochemical and cellular level.

RESULTS

Most of our knowledge about the neurobiological mechanisms of the placebo response comes from pain and Parkinson's disease, whereby the neuronal circuits involved in placebo responsiveness have been identified. In the first case, opioidergic, dopaminergic and cholecystokinergic networks have been found to be involved. In the second case, dopaminergic activation in the striatum and neuronal changes in basal ganglia have been described.

CONCLUSION

This recent research has revealed that these placebo-induced biochemical and cellular changes in a patient's brain are very similar to those induced by drugs. This new way of thinking may have profound implications both for clinical trials and for medical practice.

Network correlates of the cognitive response to levodopa in Parkinson disease

OBJECTIVE

Cognitive dysfunction is common in Parkinson disease (PD), even early in its clinical course. This disease manifestation has been associated with impaired verbal learning performance as well as abnormal expression of a specific PD-related cognitive spatial covariance pattern (PDCP). It is not known, however, how this metabolic network relates to the cognitive response to dopaminergic therapy on the individual patient level.

METHODS

We assessed treatment-mediated changes in verbal learning and PDCP expression in 17 patients with PD without dementia who underwent cognitive testing and metabolic imaging in the unmedicated and levodopa-treated conditions. We also determined whether analogous changes were present in 12 other patients with PD without dementia who were evaluated before and during the treatment of cognitive symptoms with placebo.

RESULTS

Levodopa-mediated changes in verbal learning correlated with concurrent changes in PDCP expression (r = -0.60, p < 0.01). The subset of patients with meaningful cognitive improvement on levodopa (n = 8) exhibited concurrent reductions in PDCP expression (p < 0.01) with treatment; network modulation was not evident in the remaining subjects. Notably, the levodopa cognitive response correlated with baseline PDCP levels (r = 0.70, p = 0.002). By contrast, placebo did not affect PDCP expression, even in the subjects (n = 7) with improved verbal learning during treatment.

CONCLUSIONS

These findings suggest that cognitive dysfunction in PD may respond to treatment depending upon the degree of baseline PDCP expression. Quantification of treatment-mediated network changes can provide objective information concerning the efficacy of new agents directed at the cognitive manifestations of this disease.

Is placebo acupuncture what it is intended to be?

Randomized, placebo-controlled clinical trials are recommended for evaluation of a treatment's efficacy with the goal of separating the specific effects (verum) from the non-specific ones (placebo). In order to be able to carry out placebo-controlled acupuncture trials, minimal/sham acupuncture procedures and a sham acupuncture needle has been used with the intention of being inert. However, clinical and experimental results suggest that sham/minimal acupuncture is not inert since it is reported that both verum acupuncture and sham/minimal acupuncture induce a significant alleviation of pain. This alleviation is as pronounced as the alleviation obtained with standard treatment and more obvious than the one obtained with placebo medication or by the use of waiting list controls. These results also suggest that sham acupuncture needles evoke a physiological response. In healthy individuals sham acupuncture results in activation of limbic structures, whereas a deactivation is seen in patients with pain, i.e. results from healthy individuals do not reflect what is seen in clinical conditions. Also, depending on the etiology of pain (or any under clinical condition under investigation), the response to sham acupuncture is varying. The acupuncture ritual may also be seen as an emotional focused therapy allowing for psychological re-orientation. Sham needling in such context may be as powerful as verum acupuncture. We recommend that the evaluated effects of acupuncture could be compared with those of standard treatment, also taking the individual response into consideration, before its use or non-use is established.

Fast left prefrontal rTMS acutely suppresses analgesic effects of perceived controllability on the emotional component of pain experience

The prefrontal cortex may be a promising target for transcranial magnetic stimulation (TMS) in the management of pain. It is not clear how prefrontal TMS affects pain perception, but previous findings suggest that ventral lateral and medial prefrontal circuits may comprise an important part of a circuit of perceived controllability regarding pain, stress, and learned helplessness. Although the left dorsolateral prefrontal cortex is a common TMS target for treating clinical depression as well as modulating pain, little is known about whether TMS over this area may affect perceived controllability. The present study explored the immediate effects of fast TMS over the left dorsolateral prefrontal cortex on the analgesic effects of perceived pain controllability. Twenty-four healthy volunteers underwent a laboratory pain task designed to manipulate perception of pain controllability. Real TMS, compared with sham, suppressed the analgesic benefits of perceived control on the emotional dimension of pain, but not the sensory/discriminatory dimension. Findings suggest that, at least acutely, fast TMS over the left dorsolateral prefrontal cortex may interrupt the perceived-controllability effect on the emotional dimension of pain experience. Although it is not clear whether this cortical area is directly involved with modulating perceived controllability or whether downstream effects are responsible for the present findings, it appears possible that left dorsolateral prefrontal TMS may produce analgesic effects by acting through a cortical perceived-control circuit regulating limbic and brainstem areas of the pain circuit. Despite evidence that prefrontal TMS can have analgesic effects, fast left prefrontal TMS appears to acutely suppress analgesia associated with perceived-control. This effect may be limited to the emotional dimension of pain experience.

Successful treatment with Yokukansan for behavioral and psychological symptoms of Parkinsonian dementia

OBJECTIVE

To evaluate the efficacy and safety of Yokukansan, a traditional Chinese herbal medicine, for treating behavioral and psychological symptoms of dementia (BPSD) in patients with Parkinson disease (PD; n=7) and those with PD with dementia (PDD; n=7).

BACKGROUND

BPSD are often seen in patients with senile dementia and have serious deleterious effects on the lives of patients and caregivers. Recent studies indicate that the traditional Chinese herbal medicine Yokukansan may be safe and beneficial for the treatment of BPSD patients.

METHODS

We treated 7 PD and 7 PDD patients for 4 weeks with Yokukansan and observed them without Yokukansan for 4 weeks. Changes in behavioral and psychological symptoms were evaluated every 4 weeks according to the Neuropsychiatric Inventory (NPI) scale.

RESULTS

Significant improvements in behavioral and psychological symptoms, particularly in the incidence and duration of hallucinations, were observed in most PD and PDD patients after 4 weeks of Yokukansan treatment. No significant changes were observed in the laboratory tests, cognitive function, activities of daily living, or parkinsonism.

CONCLUSION

Our results suggest that Yokukansan improves BPSD in both PD and PDD patients without worsening their cognitive function, ability to perform activities of daily living, or parkinsonism.

Comorbid pain, depression, and anxiety: multifaceted pathology allows for multifaceted treatment

The care of patients who suffer from physical pain and a psychiatric illness is typically challenging because of the complex interplay of affective, behavioral, cognitive, and physical aspects of pain. Psychiatrists are often asked to evaluate patients with pain because of a concern for comorbid depression and anxiety, and fears of suicidality as a result of pain. This article reviews the pathophysiology of comorbid pain, anxiety, and depression, along with the treatment modalities (pharmacologic, psychotherapeutic, and "alternative") that may benefit all three conditions.

Higher cortical modulation of pain perception in the human brain: Psychological determinant

Pain perception and its genesis in the human brain have been reviewed recently. In the current article, the reports on pain modulation in the human brain were reviewed from higher cortical regulation, i.e. top-down effect, particularly studied in psychological determinants. Pain modulation can be examined by gene therapy, physical modulation, pharmacological modulation, psychological modulation, and pathophysiological modulation. In psychological modulation, this article examined (a) willed determination, (b) distraction, (c) placebo, (d) hypnosis, (e) meditation, (f) qi-gong, (g) belief, and (h) emotions, respectively, in the brain function for pain modulation. In each, the operational definition, cortical processing, neuroimaging, and pain modulation were systematically deliberated. However, not all studies had featured the brain modulation processing but rather demonstrated potential effects on human pain. In our own studies on the emotional modulation on human pain, we observed that emotions could be induced from music melodies or pictures perception for reduction of tonic human pain, mainly in potentiation of the posterior alpha EEG fields, likely resulted from underneath activities of precuneous in regulation of consciousness, including pain perception. To sum, higher brain functions become the leading edge research in all sciences. How to solve the information bit of thinking and feeling in the brain can be the greatest challenge of human intelligence. Application of higher cortical modulation of human pain and suffering can lead to the progress of social humanity and civilization.

Parsing brain activity associated with acupuncture treatment in Parkinson's diseases

Acupuncture, a common treatment modality within complementary and alternative medicine, has been widely used for Parkinson's disease (PD). Using functional magnetic resonance imaging (fMRI), we explored the neural mechanisms underlying the effect of specific and genuine acupuncture treatment on the motor function in patients with PD. Three fMRI scans were performed in random order in a block design, one for verum acupuncture (VA) treatment, another one for a covert placebo (CP), and the third one for an overt placebo (OP) at the motor function implicated acupoint GB34 on the left foot of 10 patients with PD. We calculated the contrast that subtracts the blood-oxygen-level dependent (BOLD) response for the acupuncture effect (VA vs. CP) and the placebo effect (CP vs. OP). We found a significant improvement in the motor function of the affected hand after acupuncture treatment. The putamen and the primary motor cortex were activated when patients with PD received the acupuncture treatment (VA vs. CP) and these activations correlated with individual enhanced motor function. Expectation towards acupuncture modality (CP vs. OP) elicited activation over the anterior cingulate gyrus, the superior frontal gyrus, and the superior temporal gyrus. These findings suggest that acupuncture treatment might facilitate improvement in the motor functioning of patients with PD via the basal ganglia-thalamocortical circuit.

Prefrontal cortex modulates placebo analgesia

Expectations and beliefs modulate the experience of pain, which is particularly evident in placebo analgesia. The dorsolateral prefrontal cortex (DLPFC) has been associated with pain regulation and with the generation, maintenance and manipulation of cognitive representations, consistent with its role in expectation. In a heat-pain paradigm, we employed non-invasive low-frequency repetitive transcranial magnetic stimulation (rTMS) to transiently disrupt left and right DLPFC function or used the TMS device itself as a placebo, before applying an expectation-induced placebo analgesia. The results demonstrated that placebo significantly increased pain threshold and pain tolerance. While rTMS did not affect pain experience, it completely blocked placebo analgesia. These findings suggest that expectation-induced placebo analgesia is mediated by symmetric prefrontal cortex function.

The "placebo" response in osteoarthritis and its implications for clinical practice

Many observations support a major biological effect from the way in which people interpret the meaning of each component of their medical experience and the context in which this occurs. A recent systematic review of randomised controlled trials in osteoarthritis has demonstrated that the effect size of "placebo" is substantial and is usually greater than that obtained from the specific effect of an individual treatment. In the context of a randomised controlled trial, such a large placebo or "meaning" response is considered a nuisance, but in the context of clinical practice the optimisation of such meaning and contextual responses, through enhanced "care", could greatly benefit people who suffer from osteoarthritis.

Pattern of brain atrophy in elderly patients with depression revealed by voxel-based morphometry

In this study, we explored to what extent brain abnormalities can be identified in specific brain structures of patients suffering from late onset depression. We examined the structural difference in regional gray and white matter volume between 14 community-dwelling patients suffering from geriatric depression and 20 age-matched non-depressed normal subjects by voxel-based morphometry (VBM) based on magnetic resonance imaging. All subjects also underwent an extensive neuropsychological assessment. Compared with control subjects, patients with depression were impaired in measures of verbal and visual memory, construction, executive ability, and information-processing speed. VBM of gray matter revealed a significant decrease of volume in the right rostral hippocampus, in the right amygdala and in the medial orbito-frontal cortex (gyrus rectus) bilaterally. In the correlation analysis of gray matter volume with the score of the geriatric depression scale, we observed a negative correlation with the medial orbito-frontal cortex (gyrus rectus) bilaterally. There were no differences in white matter volumes between patients with depression and healthy control subjects. The most important limitation of this study was sample size. A larger sample size may have improved detection of changes not reaching significance. Furthermore, our results may not be generalizable across depression severity or to hospitalized patients. The findings are consistent with our hypothesis that depression in the elderly is associated with local gray matter dysfunction.

New insights into the placebo and nocebo responses

In modern medicine, the placebo response or placebo effect has often been regarded as a nuisance in basic research and particularly in clinical research. The latest scientific evidence has demonstrated, however, that the placebo effect and the nocebo effect, the negative effects of placebo, stem from highly active processes in the brain that are mediated by psychological mechanisms such as expectation and conditioning. These processes have been described in some detail for many diseases and treatments, and we now know that they can represent both strength and vulnerability in the course of a disease as well as in the response to a therapy. However, recent research and current knowledge raise several issues that we shall address in this review. We will discuss current neurobiological models like expectation-induced activation of the brain reward circuitry, Pavlovian conditioning, and anxiety mechanisms of the nocebo response. We will further explore the nature of the placebo responses in clinical trials and address major questions for future research such as the relationship between expectations and conditioning in placebo effects, the existence of a consistent brain network for all placebo effects, the role of gender in placebo effects, and the impact of getting drug-like effects without drugs.

Anti-TNF-alpha treatment for deep endometriosis-associated pain: a randomized placebo-controlled trial

BACKGROUND

Endometriosis is associated with an inflammatory response. Hence infliximab, an anti-TNF-alpha monoclonal antibody, might relieve pain.

METHODS

A randomized placebo-controlled trial was designed with 21 women with severe pain and a rectovaginal nodule of at least 1 cm. After 1 month of observation, three infusions of infliximab (5 mg/kg) or placebo were given. Surgery was performed 3 months later and follow-up continued for 6 months. The primary end-point was pain (dysmenorrhea, deep dyspareunia and non-menstrual pain) rated at each visit by the clinician and on a daily basis by the patient who in addition scored pain by visual analog pain scale and analgesia intake. Secondary end-points included the volume of the endometriotic nodule, pelvic tenderness and the visual appearance of endometriotic lesions at laparoscopy.

RESULTS

Pain severity decreased during the treatment by 30% in both the placebo (P < 0.001) and infliximab groups (P < 0.001). However, no effect of infliximab was observed for any of the outcome measures. After surgery, pain scores decreased in both groups to less than 20% of the initial value.

CONCLUSIONS

Infliximab appears not to affect pain associated with deep endometriosis. Treatment is associated with an important placebo effect. After surgery, pain decreases to less than 20%. Trials registration number ClinicalTrials.gov: NCT00604864.

Neurophysiology and psychobiology of the placebo response

PURPOSE OF REVIEW

The placebo literature has substantially increased in 2006 and 2007, and more and more medical and psychological subspecialties have added empirical data to our knowledge.

RECENT FINDINGS

The theoretical framework of our understanding of the placebo response needs extension to account for findings that cannot be attributed to (Pavlovian) conditioning or suggestions alone. In addition, imaging studies need to address individual responses rather than group means, and to expand beyond experimental pain research. Gender aspects have been demonstrated for the placebo response but still widely ignored, especially in neurophysiological studies. It has been shown that nocebo research needs a methodological and ethical framework that allows its exploration. Finally, analyses of clinical trial data, either as metaanalyses or as reanalyses of trial raw data, may allow us to identify factors that subsequently can be used in experimental work.

SUMMARY

Novel findings will allow better planning of clinical drug trials, better handling of clinical trial data in the future, and finally, may eventually result in improved patient management.