Background: Placebo and nocebo effects occur in clinical or laboratory medical contexts after administration of an inert treatment or as part of active treatments and are due to psychobiological mechanisms such as expectancies of the patient. Placebo and nocebo studies have evolved from predominantly methodological research into a far-reaching interdisciplinary field that is unravelling the neurobiological, behavioural and clinical underpinnings of these phenomena in a broad variety of medical conditions. As a consequence, there is an increasing demand from health professionals to develop expert recommendations about evidence-based and ethical use of placebo and nocebo effects for clinical practice. Methods: A survey and interdisciplinary expert meeting by invitation was organized as part of the 1st Society for Interdisciplinary Placebo Studies (SIPS) conference in 2017. Twenty-nine internationally recognized placebo researchers participated. Results: There was consensus that maximizing placebo effects and minimizing nocebo effects should lead to better treatment outcomes with fewer side effects. Experts particularly agreed on the importance of informing patients about placebo and nocebo effects and training health professionals in patient-clinician communication to maximize placebo and minimize nocebo effects. Conclusions: The current paper forms a first step towards developing evidence-based and ethical recommendations about the implications of placebo and nocebo research for medical practice, based on the current state of evidence and the consensus of experts. Future research might focus on how to implement these recommendations, including how to optimize conditions for educating patients about placebo and nocebo effects and providing training for the implementation in clinical practice.

Over the years, many have viewed Fibromyalgia syndrome (FMS) as a so-called "functional disorder" and patients have experienced a concomitant lack of interest and legitimacy from the medical profession. The symptoms have not been explained by peripheral mechanisms alone nor by specific central nervous system mechanisms. In this study, we objectively evaluated the cerebral response to individually calibrated pain provocations of a pain-free body region (thumbnail). The study comprised 16 female FMS patients and 16 individually age-matched controls. Brain activity was measured using functional magnetic resonance imaging (fMRI) during individually calibrated painful pressures representing 50 mm on a visual analogue scale (VAS) ranging from 0 to 100 mm. Patients exhibited higher sensitivity to pain provocation than controls as they required less pressure to evoke equal pain magnitudes (U(A)=48, p<.002). Despite lower pressures applied in patients at VAS 50 mm, the fMRI-analysis revealed no difference in activity in brain regions relating to attention and affect or regions with sensory projections from the stimulated body area. However, in the primary link in the descending pain regulating system (the rostral anterior cingulate cortex) the patients failed to respond to pain provocation. The attenuated response to pain in this brain region is the first demonstration of a specific brain region where the impairment of pain inhibition in FMS patients is expressed. These results validate previous reports of dysfunctional endogenous pain inhibition in FMS and advance the understanding of the central pathophysiologic mechanisms, providing a new direction for the development of successful treatments in FMS.

The dominant theories of human placebo effects rely on a notion that consciously perceptible cues, such as verbal information or distinct stimuli in classical conditioning, provide signals that activate placebo effects. However, growing evidence suggest that behavior can be triggered by stimuli presented outside of conscious awareness. Here, we performed two experiments in which the responses to thermal pain stimuli were assessed. The first experiment assessed whether a conditioning paradigm, using clearly visible cues for high and low pain, could induce placebo and nocebo responses. The second experiment, in a separate group of subjects, assessed whether conditioned placebo and nocebo responses could be triggered in response to nonconscious (masked) exposures to the same cues. A total of 40 healthy volunteers (24 female, mean age 23 y) were investigated in a laboratory setting. Participants rated each pain stimulus on a numeric response scale, ranging from 0 = no pain to 100 = worst imaginable pain. Significant placebo and nocebo effects were found in both experiment 1 (using clearly visible stimuli) and experiment 2 (using nonconscious stimuli), indicating that the mechanisms responsible for placebo and nocebo effects can operate without conscious awareness of the triggering cues. This is a unique experimental verification of the influence of nonconscious conditioned stimuli on placebo/nocebo effects and the results challenge the exclusive role of awareness and conscious cognitions in placebo responses.analgesia | hyperalgesia | consciousness P lacebo and nocebo effects are critical components of medical practice and clinical research. Placebo analgesia and nocebo hyperalgesia are the most robust and well studied of these effects. Learning is known to play an important role in placebo and nocebo effects and the dominant theories invoke classical conditioning and expectancies as explanatory tools (1). Both rely on a notion that the conscious perception of sensory or social stimuli, such as the cue that triggers expectancy or the conditioned stimulus in classical conditioning, are needed to obtain placebo responses. In some circumstances, conditioning may be an automatic nonconscious process, but in most cases, it seems to involve the formation of expectations (2-4). However, it is not known whether conscious perception of a conditioned stimulus is needed to elicit a conditioned response.There is a large literature suggesting that behavior can be motivated by stimuli that are not consciously perceived, because they are presented at low intensities or masked from conscious awareness (5, 6), sometimes referred to as subliminal stimuli. Nonconscious operations are considered a fundamental feature of human cognition, for example in reward processing (7,8), fear learning (9, 10), and social behavior (11,12). Furthermore, evidence suggests that conditioned responses may be acquired outside of conscious awareness (13-15). Neuroimaging studies of the human brain suggest that certain structures, such as the striatum and ...

The results correspond with previous studies on ACT for chronic pain and suggest the utility of ACT for FM as well as the role of psychological inflexibility as a mediator of improvement.

Interventions based on Cognitive Behavioral Therapy (CBT) are widely used to treat chronic pain, but the brain mechanisms responsible for these treatment effects are poorly understood. The aim of this study was to validate the relevance of the cortical control theory in response to an exposure-based form of CBT, Acceptance and Commitment Therapy, in patients with chronic pain. Forty-three female patients diagnosed with fibromyalgia syndrome were enrolled in a randomized, 12-week, waiting-list controlled clinical trial (CBT n=25; controls n=18). CBT was administered in groups of six patients during 12 weekly sessions. Functional magnetic resonance imaging (fMRI) during pressure-evoked pain was assessed before and after treatment or the 12-week period. Self-report questionnaires of depression and anxiety were administered pre- and posttreatment as well as 3 months following end of treatment. Patients treated with CBT reported larger improvement of fibromyalgia on the Patient Global Impression of Change measure, and improved depression and anxiety symptoms, compared to the waiting-list controls. However, there were no effects on clinical pain or pain sensitivity measures. An analysis of fMRI scans revealed that CBT led to increased activations in the ventrolateral prefrontal/lateral orbitofrontal cortex; regions associated with executive cognitive control. We suggest that CBT changes the brain's processing of pain through an altered cerebral loop between pain signals, emotions, and cognitions; leading to increased access to executive regions for reappraisal of pain. Our data thereby support our hypothesis about the activation of a cortical control mechanism in response to CBT treatment in chronic pain.

BackgroundThere is evidence for augmented processing of pain and impaired endogenous pain inhibition in Fibromyalgia syndrome (FM). In order to fully understand the mechanisms involved in FM pathology, there is a need for closer investigation of endogenous pain modulation. In the present study, we compared the functional connectivity of the descending pain inhibitory network in age-matched FM patients and healthy controls (HC).We performed functional magnetic resonance imaging (fMRI) in 42 subjects; 14 healthy and 28 age-matched FM patients (2 patients per HC), during randomly presented, subjectively calibrated pressure pain stimuli. A seed-based functional connectivity analysis of brain activity was performed. The seed coordinates were based on the findings from our previous study, comparing the fMRI signal during calibrated pressure pain in FM and HC: the rostral anterior cingulate cortex (rACC) and thalamus.ResultsFM patients required significantly less pressure (kPa) to reach calibrated pain at 50 mm on a 0–100 visual analogue scale (p < .001, two-tailed). During fMRI scanning, the rACC displayed significantly higher connectivity to the amygdala, hippocampus, and brainstem in healthy controls, compared to FM patients. There were no regions where FM patients showed higher rACC connectivity. Thalamus showed significantly higher connectivity to the orbitofrontal cortex in healthy controls but no regions showed higher thalamic connectivity in FM patients.ConclusionPatients with FM displayed less connectivity within the brain’s pain inhibitory network during calibrated pressure pain, compared to healthy controls. The present study provides brain-imaging evidence on how brain regions involved in homeostatic control of pain are less connected in FM patients. It is possible that the dysfunction of the descending pain modulatory network plays an important role in maintenance of FM pain and our results may translate into clinical implications by using the functional connectivity of the pain modulatory network as an objective measure of pain dysregulation.

Objective There is vast evidence for brain aberrations in patients with fibromyalgia (FM) and it is possible that central plasticity is critical for the transition from acute to chronic pain. However, the relationship between brain structure and function is poorly investigated. Methods The present study, including 26 FM patients and 13 age- and gender-matched healthy controls, investigated the differences between patients and controls regarding functional connectivity during intermittent pressure pain and measures of brain structure. Magnetic resonance imaging (MRI) was used to obtain high-resolution anatomical images and functional MRI scans for measures of pain-evoked brain activity. Results FM patients displayed a distinct overlap between decreased cortical thickness, brain volumes and measures of functional regional coherence in the rostral anterior cingulate cortex. The morphometric changes were more pronounced with longer exposure to FM pain. In addition, we found associations between structural and functional changes in the mesolimbic areas of the brain and comorbid depressive symptoms in FM patients. Conclusion The combined integration of structural and functional measures allowed for a unique characterization of the impact of FM pain on the brain. Our data may lead to the identification of early structural and functional brain alterations in response to pain, which could be used to develop markers to predict the development of FM and other pain disorders.

Identifying patients who are potential placebo responders has major implications for clinical practice and trial design. Catechol-O-methyltransferase (COMT), an important enzyme in dopamine catabolism plays a key role in processes associated with the placebo effect such as reward, pain, memory and learning. We hypothesized that the COMT functional val158met polymorphism, was a predictor of placebo effects and tested our hypothesis in a subset of 104 patients from a previously reported randomized controlled trial in irritable bowel syndrome (IBS). The three treatment arms from this study were: no-treatment (“waitlist”), placebo treatment alone (“limited”) and, placebo treatment “augmented” with a supportive patient-health care provider interaction. The primary outcome measure was change from baseline in IBS-Symptom Severity Scale (IBS-SSS) after three weeks of treatment. In a regression model, the number of methionine alleles in COMT val158met was linearly related to placebo response as measured by changes in IBS-SSS (p = .035). The strongest placebo response occurred in met/met homozygotes treated in the augmented placebo arm. A smaller met/met associated effect was observed with limited placebo treatment and there was no effect in the waitlist control. These data support our hypothesis that the COMT val158met polymorphism is a potential biomarker of placebo response.