Association Between Placebo-Activated Neural Systems and Antidepressant Responses: Neurochemistry of Placebo Effects in Major Depression

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.

Is There a Role for GPCR Agonist Radiotracers in PET Neuroimaging?

Positron emission tomography (PET) is a molecular imaging modality that enables in vivo exploration of metabolic processes and especially the pharmacology of neuroreceptors. G protein-coupled receptors (GPCRs) play an important role in numerous pathophysiologic disorders of the central nervous system. Thus, they are targets of choice in PET imaging to bring proof concept of change in density in pathological conditions or in pharmacological challenge. At present, most radiotracers are antagonist ligands. In vitro data suggest that properties differ between GPCR agonists and antagonists: antagonists bind to receptors with a single affinity, whereas agonists are characterized by two different affinities: high affinity for receptors that undergo functional coupling to G-proteins, and low affinity for those that are not coupled. In this context, agonist radiotracers may be useful tools to give functional images of GPCRs in the brain, with high sensitivity to neurotransmitter release. Here, we review all existing PET radiotracers used from animals to humans and their role for understanding the ligand-receptor paradigm of GPCR in comparison with corresponding antagonist radiotracers.

Nicotinic treatment of post-chemotherapy subjective cognitive impairment: a pilot study

PURPOSE

Persistent chemotherapy-related cognitive impairment (pCRCI) is commonly reported following cancer treatment and negatively affects quality of life; however, there is currently no pharmacological treatment indicated for pCRCI. This pilot study obtained preliminary data regarding the use of transdermal nicotine patches as a therapeutic strategy for women with pCRCI to (1) reduce subjective cognitive complaints and (2) enhance objective cognitive performance in breast, colon, lymphoma, or ovarian cancer survivors with pCRCI.

METHODS

Participants were randomized to either placebo (n = 11) or transdermal nicotine (n = 11) for 6 weeks, followed by 2 weeks of treatment withdrawal for a total of 8 weeks. Participants were assessed using both subjective and objective measures of cognitive functioning at five visits before, during, and after treatment.

RESULTS

Over the course of the study, women in both groups improved substantially in severity of self-reported cognitive complaints measured by Functional Assessment of Cancer Therapy-Cognitive Function Perceived Cognitive Impairments regardless of treatment arm. Additionally, objective cognitive performance measures improved in both groups; however, there was no significant difference in improvement between groups.

CONCLUSIONS

Due to a large placebo response, we were unable to determine if a drug effect was present. However, we did observe substantial improvement in self-reported cognitive symptoms, likely resulting from factors related to participation in the trial rather than specific drug treatment effects.

TRIAL REGISTRATION

The study was registered with clinicaltrials.gov (trial registration: NCT02312943).

IMPLICATIONS FOR CANCER SURVIVORS

These results suggest that women with pCRCI can exhibit improvement in subjective cognition, with attention paid to symptoms and close follow-up over a short period of time.

Neuroimaging Studies of Antidepressant Placebo Effects: Challenges and Opportunities

Over the last two decades, neuroscientists have used antidepressant placebo probes to examine the biological mechanisms implicated in expectancies of mood improvement.However, findings from these studies have yet to elucidate a model-based theory that would explain the mechanisms through which antidepressant expectancies evolve to induce persistent mood changes. Compared to other fields, the development of experimental models of antidepressant placebo effects faces significant challenges, such as the delayed mechanism of action of conventional antidepressants and the complex internal dynamics of mood. Still, recent neuroimaging studies of antidepressant placebo effects have shown remarkable similarities to those observed in other disciplines (e.g., placebo analgesia), such as placebo-induced increased µ-opioid signaling and blood-oxygen-level dependent (BOLD) responses in areas involved in cognitive control, the representation of expected values and reward and emotional processing. This review will summarize these findings and the challenges and opportunities that arise from applying methodologies used in the field of placebo analgesia into the field of antidepressant placebo effects.

Neural mechanisms of expectancy-based placebo effects in antidepressant clinical trials

BACKGROUND

Patient expectancy of therapeutic improvement is a primary mediator of placebo effects in antidepressant clinical trials, but its mechanisms are poorly understood. This study employed a novel antidepressant trial design, with integrated functional magnetic resonance imaging (fMRI), to manipulate patient outcome expectancy and examine its neural mediators.

METHOD

Twenty-three depressed outpatients, in a randomized controlled trial were assigned to either Open (high outcome expectancy) or Placebo-controlled (low outcome expectancy) treatment with citalopram for eight weeks. fMRI scans were acquired before and after the expectancy manipulation (before medication treatment), while participants performed a masked emotional face task. Focusing on an amygdala region-of-interest (ROI), we tested a model where reduction in amygdala activation mediated outcome expectancy effects on the slope of change in depressive symptoms.

RESULTS

Following the manipulation, significant differences between conditions were found in neural activation changes in the amygdala, as well as in superior temporal gyrus, insula, and thalamus. Findings support the proposed mediation model according to which activation in the left amygdala ROI decreased significantly in the Open as opposed to the Placebo-controlled group following randomization (p = 0.009) for sad vs. neutral face contrast. The reduced left amygdala activation, in turn, was a significant predictor of decreased depressive symptoms during the trial (p = 0.007), and the mediation model was significant.

CONCLUSIONS

Results from this study, the first designed to identify the neural mechanisms of expectancy augmentation in an antidepressant randomized control trial, suggest that therapeutic modulation of amygdala activity may be an important pathway by which patient outcome expectancy influences depressive symptoms. CLINICALTRIALS.

GOV IDENTIFIER

NCT01919216; Trial name: Placebo Effects in the Treatment of Depression: Cognitive and Neural Mechanisms, URL: https://clinicaltrials.gov/ct2/show/NCT01919216.

The placebo and its effects: A psychoneuroendocrinological perspective

Placebos are usually employed deceptively in clinical trials in order to control for non-specific effects. However, since placebos themselves have been found to cause clinically relevant changes and in some cases are indistinguishable from the verum they are tested against, this theoretically inert, but practically effective intervention has become a scientific discipline in its own right. In this review, it is argued that placebos are generic and genuine biopsychosocial interventions and as such are highly interesting candidates for a psychoneuroendocrinological perspective. Yet, despite a considerable conceptual proximity between explanatory models of placebos and their effects with psychoneuroendocrine models and findings, placebos have thus far not been subject to systematic psychoneuroendocrine examination. Consequently, it would be highly interesting and informative to make placebos the target of psychoneuroendocrine scrutiny.

Impact of placebo arms on outcomes in antidepressant trials: systematic review and meta-regression analysis

Background

There is debate in the literature as to whether inclusion of a placebo arm may alter characteristics of antidepressant trials. However, previous research has focused on response rates of various antidepressants on average only, ignoring potential differences among drugs or other aspects of trial findings. Little is known about the impact of a placebo arm on all-cause dropout and dropout due to adverse events.

Methods

We carried out a systematic review of published and unpublished double-blind randomized controlled trials (RCTs) for the acute treatment of unipolar major depression (update: January 2016). The probability of being allocated to placebo (π) was the exposure of interest, and we examined its influence on responders (efficacy), all-cause dropouts (acceptability) and dropouts due to adverse events (tolerability), while accounting for differences in drugs, trials and patient characteristics in multivariate random effects meta-regression.

Results

We included 421 studies (68 305 participants) comparing 16 antidepressants or placebo; π ranged from 20% to 50%. Response rate was lower [risk ratio (RR) 0.87; 95% confidence interval (CI) 0.83, 0.92] and all-cause dropout rate higher (RR 1.19; 95% CI 1.08, 1.31) for the same antidepressants in placebo-controlled trials compared with head-to-head trials. The probability of responding decreased by 3% (95% CI 2-5%) for every 10% increase in π, whereas the risk of all-cause dropout increased by 4% (95% CI 1-7%). Tolerability was unaffected by π. Response rate was inversely correlated with dropouts due to any cause (correlation coefficient -0.48; 95% CI -0.58, -0.36) and due to adverse events (-0.34; 95% CI -0.44, -0.23).

Conclusions

For the same antidepressant, response rate was on average smaller and dropouts higher when placebo was included; however, no association was found with dropouts due to adverse events. Decreased patient expectations, larger dropout rates and use of inappropriate statistical methods to impute missing data may explain this phenomenon. The findings call for caution in the integration of randomized evidence involving placebo arms.

Multidimensional imaging techniques for prediction of treatment response in major depressive disorder

A large number of studies have attempted to use neuroimaging tools to aid in treatment prediction models for major depressive disorder (MDD). Most such studies have reported on only one dimension of function and prediction at a time. In this study, we used three different tasks across domains of function (emotion processing, reward anticipation, and cognitive control, plus resting state connectivity completed prior to start of medication to predict treatment response in 13-36 adults with MDD. For each experiment, adults with MDD were prescribed only label duloxetine (all experiments), whereas another subset were prescribed escitalopram. We used a KeyNet (both Task derived masks and Key intrinsic Network derived masks) approach to targeting brain systems in a specific match to tasks. The most robust predictors were (Dichter et al., 2010) positive response to anger and (Gong et al., 2011) negative response to fear within relevant anger and fear TaskNets and Salience and Emotion KeyNet (Langenecker et al., 2018) cognitive control (correct rejections) within Inhibition TaskNet (negative) and Cognitive Control KeyNet (positive). Resting state analyses were most robust for Cognitive control Network (positive) and Salience and Emotion Network (negative). Results differed by whether an -fwhm or -acf (more conservative) adjustment for multiple comparisons was used. Together, these results implicate the importance of future studies with larger sample sizes, multidimensional predictive models, and the importance of using empirically derived masks for search areas.

Development and validation of a prediction model for the probability of responding to placebo in antidepressant trials: a pooled analysis of individual patient data

BACKGROUND

Identifying potential placebo responders among apparent drug responders is critical to dissect drug-specific and nonspecific effects in depression.

OBJECTIVE

This project aimed to develop and test a prediction model for the probability of responding to placebo in antidepressant trials. Such a model will allow us to estimate the probability of placebo response among drug responders in antidepressants trials.

METHODS

We identified all placebo-controlled, double-blind randomised controlled trials (RCTs) of second generation antidepressants for major depressive disorder conducted in Japan and requested their individual patient data (IPD) to pharmaceutical companies. We obtained IPD (n=1493) from four phase II/III RCTs comparing mirtazapine, escitalopram, duloxetine, paroxetine and placebo. Out of 1493 participants in the four clinical trials, 440 participants allocated to placebo were included in the analyses. Our primary outcome was response, defined as 50% or greater reduction on Hamilton Rating Scale for Depression at study endpoint. We used multivariable logistic regression to develop a prediction model. All available candidate of predictor variables were tested through a backward variable selection and covariates were selected for the prediction model. The performance of the model was assessed by using Hosmer-Lemeshow test for calibration and the area under the ROC curve for discrimination.

FINDINGS

Placebo response rates differed between 31% and 59% (grand average: 43%) among four trials. Four variables were selected from all candidate variables and included in the final model: age at onset, age at baseline, bodily symptoms, and study-level difference. The final model performed satisfactorily in terms of calibration (Hosmer-Lemeshow p=0.92) and discrimination (the area under the ROC curve (AUC): 0.70).

CONCLUSIONS

Our model is expected to help researchers discriminate individuals who are more likely to respond to placebo from those who are less likely so.

CLINICAL IMPLICATIONS

A larger sample and more precise individual participant information should be collected for better performance. Examination of external validity in independent datasets is warranted.

TRIAL REGISTRATION NUMBER

CRD42017055912.

Current management strategies for the pain of elderly patients with burning mouth syndrome: a critical review

Burning Mouth Syndrome (BMS), a chronic intraoral burning sensation or dysesthesia without clinically evident causes, is one of the most common medically unexplained oral symptoms/syndromes. Even though the clinical features of BMS have been astonishingly common and consistent throughout the world for hundreds of years, BMS remains an enigma and has evolved to more intractable condition. In fact, there is a large and growing number of elderly BMS patients for whom the disease is accompanied by systemic diseases, in addition to aging physical change, which makes the diagnosis and treatment of BMS more difficult. Because the biggest barrier preventing us from finding the core pathophysiology and best therapy for BMS seems to be its heterogeneity, this syndrome remains challenging for clinicians. In this review, we discuss currently hopeful management strategies, including central neuromodulators (Tricyclic Antidepressants - TCAs, Serotonin, and Norepinephrine Reuptake Inhibitors - SNRIs, Selective Serotonin Reuptake Inhibitors - SSRIs, Clonazepam) and solutions for applying non-pharmacology approaches. Moreover, we also emphasize the important role of patient education and anxiety management to improve the patients’ quality of life. A combination of optimized medication with a short-term supportive psychotherapeutic approach might be a useful solution.

Low-dose augmentation with buprenorphine increases emotional reactivity but not reward activity in treatment resistant mid- and late-life depression

Buprenorphine is currently being studied for treatment-resistant depression because of its rapid effect, relative safety, and unique pharmacodynamics. To understand the neural impact of buprenorphine in depression, we examined acute limbic and reward circuit changes during an intervention with low-dose buprenorphine augmentation pharmacotherapy. Mid and late-life adults with major depression (N = 31) who did not completely respond to an adequate trial of venlafaxine were randomized to augmentation with low-dose buprenorphine or matching placebo. We investigated early neural changes using functional magnetic resonance imaging (fMRI) from pre-randomization to 3 weeks using both an emotional reactivity task and a gambling task. We tested if: 1) there were significant neural changes acutely per intervention group, and 2) if acute neural changes were associated with depressive symptom change over 8 weeks using both the total score and the dysphoria subscale of the Montgomery Asberg Depression Rating Scale. Participants in both the buprenorphine and placebo groups showed similar changes in depressive symptoms. Neither the emotional reactivity nor gambling task resulted in significant neural activation changes from pre-randomization to 3-weeks. In both groups, increases in rostral anterior cingulate (rACC) and ventromedial prefrontal cortex (vmPFC) activation during the emotional reactivity task were associated with overall symptom improvement. In the buprenorphine but not the placebo group, increased activation in left anterior insula (aINS) and bilateral middle frontal gyrus (MFG) was associated with improvement on the dysphoria subscale. Activation changes in the reward task were not associated with buprenorphine. This is the first study to show an association between acute neural changes during emotion reactivity and changes in depression severity with buprenorphine treatment.

Endogenous opioid system dysregulation in depression: implications for new therapeutic approaches

The United States is in the midst of an opioid addiction and overdose crisis precipitated and exacerbated by use of prescription opioid medicines. The majority of opioid prescriptions are dispensed to patients with comorbid mood disorders including major depressive disorder (MDD). A growing body of research indicates that the endogenous opioid system is directly involved in the regulation of mood and is dysregulated in MDD. This involvement of the endogenous opioid system may underlie the disproportionate use of opioids among patients with mood disorders. Emerging approaches to address endogenous opioid dysregulation in MDD may yield novel therapeutics that have a low or absent risk of abuse and addiction relative to µ-opioid agonists. Moreover, agents targeting the endogenous opioid system would be expected to yield clinical benefits qualitatively different from conventional monaminergic antidepressants. The development of safe and effective agents to treat MDD-associated endogenous opioid dysregulation may represent a distinct and currently underappreciated means of addressing treatment resistant depression with the potential to attenuate the on-going opioid crisis.

Predictors of Placebo Response in Pharmacological Clinical Trials of Negative Symptoms in Schizophrenia: A Meta-regression Analysis

We conducted a meta-regression analysis of all double-blind, randomized, placebo-controlled clinical trials (DBRCTs) reporting effects of drug and placebo on negative symptoms in people with stable schizophrenia and predominant or prominent negative symptoms to assess predictors of placebo response in these individuals. We used Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines for systematic reviews and meta-analyses to conduct a systematic literature search to identify DBRCTs assessing treatment efficacy on negative symptoms, as primary outcome, in patients with stable schizophrenia and predominant or prominent negative symptoms. We used Cohen's d, with 95% CIs, as the effect size measure for placebo response, based on negative symptom change scores from baseline to endpoint (range 4 to 24 wk) in the placebo-treated group. We included 18 DBRCTs from 17 publications, assessing the effect of 13 drugs vs placebo on negative symptoms and comprising 998 patients, in the meta-regression analyses. Overall, drugs showed greater efficacy than placebo in reducing negative symptoms, with small effect size (Cohen's d: 0.208, P = .020). Placebo response was significant (P < .001) and clinically relevant (Cohen's d: 2.909), but there was significant heterogeneity and high risk of publication bias. Multivariable meta-regression analyses showed that larger numbers of arms in the trial, larger numbers of study sites and industry sponsorship were significant moderators of placebo response in this population. Our results suggest that some clinical trial design and operational factors affect the level of placebo response in such studies, thus highlighting the need for designs better suited to assess these outcomes.

In search of decoding the syntax of the bioelements in human hair - A critical overview

The principles and practice of assessing the human body nutritional status or its environmental exposure through hair bioelement analysis are presented; herein the term "bioelements" is used as a common denominator for the major elements, trace elements and ultra-trace elements that are found in the human body. The accumulation of bioelements in the hair followed the statistical Power Law and the resulting sigmoid curve can be zoned into five regions in the ascending order of abundance (Low, Marginal, Adequate, High, and Excessive). The Adequate linear region of the bioassay sigmoid curve may be further subdivided into Low adequate, Recommended, and Ample adequate sub regions in a 60:30:10 ratio. Phosphorus was the most invariant bioelement since its hair concentration varies minimally regardless of the geographical place of living, the twenty years' time interval between the analyses, sex, race and instrumentation, i.e., atomic absorption spectrometry (AAS) atomic emission spectrometry (AES), and inductively plasma mass spectrometry (ICP MS). The osteotrophic (bone seeking) bioelements: Ca, Mg, and Sr, were 2.5 times more abundant in the hair of women than men. Two principal electrolytes of the body (Na, K) of the multi-bioelement hair profile were markedly increased in the depressed subjects diagnosed according to the American Psychiatric Association MSD-IV classification criteria. This increase in the hair Na and K of the depressed subjects was also associated with the decrease of vasopressin in the peripheral blood. The factor analysis revealed strong association of depression with sex (women > men in a 2.5:1 ratio), and with the metals from the Nieboer-Richardson series which form strong covalent bonds with proteins. We propose that the biological roots of depression are related to the non-specific impairment of the intracellular osmotic balance and ionic gradient due to the Na⁺K⁺ATPase failure from whatever cause acting either separately or in combination. We also put forward the idea of how children's autism may be related to a disproportional growth rate of various organs and tissues if children are fed up to their maximal genetic growth capacity. Finally, we have suggested the hypothesis on how the syntax or integration of the internal metabolic wiring of the bioelements in the body may occur. We have suggested the hypothetical existence of two complex distinct five-bioelement "rotors", the P-rotor and the N-rotor, where the P-rotor integrates the mileau interior (Na, K) ions with the perception/excitability (Mg, Ca) ions. Thus, the complex five element interdependence is cross related to P which provides the energy from the phosphorus of the DNA nucleotide backbone. The hair multi-bioelement profile analysis allows us to envisage the more complex structural metabolic features that bioelements are playing in our bodies.

Examination of an Integrative Health Care Model for Social Work Practice

Social work professionals would benefit by including integrative medicine programs and practices in their framework of practice and service delivery to clients. In our rapidly changing health care environment, using a model that provides a more comprehensive and empowering approach to addressing the medical and psychological needs of our clients is warranted. Discussion of holistic social work practice and implications for social work education and training will be examined through a review of the research and clinical application of a mind-body program titled the Relaxation Response Resiliency Program (3RP). This client-centered, strengths-based program can be used in conjunction with traditional therapies to empower clients to take part in their own health care by teaching noninvasive, self-care, and user-friendly techniques. New research from the Benson-Henry Institute for Mind Body Medicine has demonstrated a reduction in service utilization and cost savings from participation in 3RP. Research on this resiliency health care model will be of interest to social work practitioners, educators, and policymakers alike.

Prefrontal expectancy and reinforcement-driven antidepressant placebo effects

Placebo responses in depression exemplify how expectancies and appraisals impact mood. Cognitive and neural mechanisms underlying these responses are still poorly understood, partly due to the difficulty of simulating antidepressant effects and manipulating mood experimentally. To address these challenges, we developed an acute antidepressant placebo experiment involving the intravenous administration of a "fast-acting antidepressant" and a trial-by-trial sham fMRI "neurofeedback" manipulation, purporting to reveal mood-relevant neural responses. Twenty volunteers with major depression underwent this experiment while rating their expected and actual mood improvement. Mixed-effects analyses of trial-by-trial ratings revealed that the "drug" infusion cues induced higher expectancies of mood improvement, while both the "drug" infusion cue and the sham neurofeedback induced a reported mood improvement. Neurofeedback of greater magnitude, compared to lower magnitude, recruited the lateral prefrontal cortex (lPFC). Individuals with greater lPFC responses to neurofeedback displayed: (1) greater effect of previous mood improvement on expectancy ratings and (2) greater effect of sham neurofeedback on mood improvement. Behavioral antidepressant placebo effects were additionally moderated by changes in peripheral β-endorphin plasma levels and depressive symptomatology. These data demonstrate the feasibility of trial-by-trial manipulation of antidepressant placebo-associated expectancies and their reinforcement. We provide initial insights into the role of the lPFC in the interplay between placebo-induced expectancies and mood, as well as preliminary evidence for the role of the opioid system in antidepressant placebo effects.

GOALS FOR MEDICAL TREATMENT IN OBESITY AND PREDIABETES: IMPROVING OUTCOMES FOR BOTH

OBJECTIVE

The purpose of this review is to expose the surprising prevalence of diabetes-related complications in people with persistent prediabetes, and hence, to expand the paradigm of diabetes prevention to include the prevention of complications related to both hyperglycemia and obesity.

METHODS

Published literature was reviewed.

RESULTS

Approximately 84 million Americans have prediabetes, 85% of whom are overweight or obese. Although the incidence of diabetes-related complications is lower in people with prediabetes versus those with type 2 diabetes, the overall prevalence is virtually identical. Furthermore, many people with prediabetes not only suffer from the complications related to hyperglycemia, they also experience complications of obesity. Treating obesity as a disease has the potential to prevent complications of both hyperglycemia and obesity. Emerging data reveal the untapped potential for clinicians to enhance the effectiveness of anti-obesity medications through a mindful health care delivery style. This involves an understanding and ethical utilization of the placebo effect in conjunction with active medical therapy. This approach is not intended to mislead patients but rather to activate neurocircuitry that synergizes with the central action of the approved anti-obesity medications to potentiate weight loss.

CONCLUSION

Mindful administration of anti-obesity medications has the potential for widespread health benefits in people with obesity and prediabetes.

ABBREVIATIONS

ADA = American Diabetes Association; DPP = Diabetes Prevention Program; CVD = cardiovascular disease.

Pretreatment and early-treatment cortical thickness is associated with SSRI treatment response in major depressive disorder

To date, there are no biomarkers for major depressive disorder (MDD) treatment response in clinical use. Such biomarkers could allow for individualized treatment selection, reducing time spent on ineffective treatments and the burden of MDD. In search of such a biomarker, multisite pretreatment and early-treatment (1 week into treatment) structural magnetic resonance (MR) images were acquired from 184 patients with MDD randomized to an 8-week trial of the selective serotonin reuptake inhibitor (SSRI) sertraline or placebo. This study represents a large, multisite, placebo-controlled effort to examine the association between pretreatment differences or early-treatment changes in cortical thickness and treatment-specific outcomes. For standardization, a novel, robust site harmonization procedure was applied to structural measures in a priori regions (rostral and caudal anterior cingulate, lateral orbitofrontal, rostral middle frontal, and hippocampus), chosen based on previously published reports. Pretreatment cortical thickness or volume did not significantly associate with SSRI response. Thickening of the rostral anterior cingulate cortex in the first week of treatment was associated with better 8-week responses to SSRI (p = 0.010). These findings indicate that frontal lobe structural alterations in the first week of treatment may be associated with long-term treatment efficacy. While these associational findings may help to elucidate the specific neural targets of SSRIs, the predictive accuracy of pretreatment or early-treatment structural alterations in classifying treatment remitters from nonremitters was limited to 63.9%. Therefore, in this large sample of adults with MDD, structural MR imaging measures were not found to be clinically translatable biomarkers of treatment response to SSRI or placebo.

Brain and psychological determinants of placebo pill response in chronic pain patients

The placebo response is universally observed in clinical trials of pain treatments, yet the individual characteristics rendering a patient a ‘placebo responder’ remain unclear. Here, in chronic back pain patients, we demonstrate using MRI and fMRI that the response to placebo ‘analgesic’ pills depends on brain structure and function. Subcortical limbic volume asymmetry, sensorimotor cortical thickness, and functional coupling of prefrontal regions, anterior cingulate, and periaqueductal gray were predictive of response. These neural traits were present before exposure to the pill and most remained stable across treatment and washout periods. Further, psychological traits, including interoceptive awareness and openness, were also predictive of the magnitude of response. These results shed light on psychological, neuroanatomical, and neurophysiological principles determining placebo response in RCTs in chronic pain patients, and they suggest that the long-term beneficial effects of placebo, as observed in clinical settings, are partially predictable.

People vary in the extent to which they feel better after taking an inert, placebo, treatment, but the basis for individual placebo response is unclear. Here, the authors show how brain structural and functional variables, as well as personality traits, predict placebo response in those with chronic back pain.

The nocebo effect: a clinical challenge in the era of biosimilars

INTRODUCTION

The nocebo effect is defined as a negative effect of a pharmacological or non-pharmacological medical treatment that is induced by patients' expectations, and that is unrelated to the physiological action of the treatment. The nocebo effect is an important clinical challenge in the current era of biosimilars. Areas covered: This review aims to answer five key questions about the nocebo effect, namely to reveal its definition, pathophysiology, clinical relevance, contributing factors, and management. Expert commentary: The nocebo effect lowers patients' quality of life and negatively affects treatment adherence rates in biosimilar-treated patients. It may negatively impact on the cost-savings of biosimilars. Health-care providers in charge of biosimilar-treated patients need to be aware of the nocebo effect and adopt strategies to minimize it. They have to be well-informed and confident about the existing evidence about biosimilars. A good patient-physician relationship will improve patients' acceptance of biosimilars, and limits the risk of inappropriate negative bias and the nocebo effect.

Are Blue Pills Better Than Green? How Treatment Features Modulate Placebo Effects

Treatment-related expectations are important predictors for placebo effects in various medical conditions. They are formed by verbal and nonverbal cues during the administration of treatments, such as verbal suggestions, conscious and unconscious associations with previous treatments, characteristics of patients and health-care providers as well as perceptual characteristics of the treatment. This review provides an overview of studies that aimed to elucidate the impact of treatment characteristics on expectations and placebo effects. Results show that high price, brand label, the use of invasive placebos and high placebo dose increase the expectations toward the beneficial effect of a placebo treatment, which in turn boost the placebo effect. Neuroimaging studies provide first insights into the neurobiological mechanisms underlying these differential placebo effects.

Pretreatment Rostral Anterior Cingulate Cortex Theta Activity in Relation to Symptom Improvement in Depression: A Randomized Clinical Trial

IMPORTANCE

Major depressive disorder (MDD) remains challenging to treat. Although several clinical and demographic variables have been found to predict poor antidepressant response, these markers have not been robustly replicated to warrant implementation in clinical care. Increased pretreatment rostral anterior cingulate cortex (rACC) theta activity has been linked to better antidepressant outcomes. However, no prior study has evaluated whether this marker has incremental predictive validity over clinical and demographic measures.

OBJECTIVE

To determine whether increased pretreatment rACC theta activity would predict symptom improvement regardless of randomization arm.

DESIGN, SETTING, AND PARTICIPANTS

A multicenter randomized clinical trial enrolled outpatients without psychosis and with chronic or recurrent MDD between July 29, 2011, and December 15, 2015 (Establishing Moderators and Biosignatures of Antidepressant Response for Clinical Care [EMBARC]). Patients were consecutively recruited from 4 university hospitals: 634 patients were screened, 296 were randomized to receive sertraline hydrochloride or placebo, 266 had electroencephalographic (EEG) recordings, and 248 had usable EEG data. Resting EEG data were recorded at baseline and 1 week after trial onset, and rACC theta activity was extracted using source localization. Intent-to-treat analysis was conducted. Data analysis was performed from October 7, 2016, to January 19, 2018.

INTERVENTIONS

An 8-week course of sertraline or placebo.

MAIN OUTCOMES AND MEASURES

The 17-item Hamilton Rating Scale for Depression score (assessed at baseline and weeks 1, 2, 3, 4, 6, and 8).

RESULTS

The 248 participants (160 [64.5%] women, 88 [35.5%] men) with usable EEG data had a mean (SD) age of 36.75 (13.15) years. Higher rACC theta activity at both baseline (b = -1.05; 95% CI, -1.77 to -0.34; P = .004) and week 1 (b = -0.83; 95% CI, -1.60 to -0.06; P < .04) predicted greater depressive symptom improvement, even when controlling for clinical and demographic variables previously linked with treatment outcome. These effects were not moderated by treatment arm. The rACC theta marker, in combination with clinical and demographic variables, accounted for an estimated 39.6% of the variance in symptom change (with 8.5% of the variance uniquely attributable to the rACC theta marker).

CONCLUSIONS AND RELEVANCE

Increased pretreatment rACC theta activity represents a nonspecific prognostic marker of treatment outcome. This is the first study to date to demonstrate that rACC theta activity has incremental predictive validity.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01407094.

Systematic review with meta-analysis: endoscopic and histologic placebo rates in induction and maintenance trials of ulcerative colitis

BACKGROUND

Regulatory requirements for claims of mucosal healing in ulcerative colitis (UC) will require demonstration of both endoscopic and histologic healing. Quantifying these rates is essential for future drug development.

AIMS

To meta-analyse endoscopic and histologic placebo response and remission rates in UC randomised controlled trials (RCTs) and identify factors influencing these rates.

METHODS

MEDLINE, EMBASE and the Cochrane Library were searched from inception to March 2017 for placebo-controlled trials of pharmacological interventions for UC. Endoscopic and histologic placebo rates were pooled by random effects. Mixed effects univariable and multivariable meta-regression was used to evaluate the influence of patient, intervention and trial-related study-level covariates on these rates.

RESULTS

Fifty-six induction (placebo n = 4171) and 8 maintenance trials (placebo n = 1011) were included. Pooled placebo endoscopic remission and response rates for induction trials were 23% [95 confidence interval (CI) 19-28%] and 35% [95% CI 27-42%] respectively, and 20% [95% CI 16-24%] for maintenance of remission. The pooled histologic placebo remission rate was 14% [95% CI 8-22%] for induction trials. High heterogeneity was observed for all outcomes (I² 56.2%-88.3%). On multivariable meta-regression, central endoscopy reading was associated with significantly lower endoscopic placebo remission rates (16% vs 25%; OR = 0.52, [95% CI 0.29-0.92], P = 0.03). On univariable meta-regression, higher histologic placebo remission was associated with concomitant corticosteroids (OR = 1.17 [95% CI 1.08-1.26], P < 0.0001, per 10% increase in corticosteroid use).

CONCLUSIONS

Placebo endoscopic and histologic rates range from 14% to 35% in UC RCTs but are highly heterogeneous. Outcome standardisation may reduce heterogeneity and is needed in this field.

Changes in brain connectivity during a sham-controlled, transcranial magnetic stimulation trial for depression

BACKGROUND

The subgenual anterior cingulate cortex (sgACC) has been implicated in major depressive disorder (MDD), and this study evaluated sgACC connectivity before and after repetitive transcranial magnetic stimulation (rTMS) treatment.

METHODS

Thirty-two MDD patients entered a sham-controlled, double-blinded, randomized trial of rTMS to the left dorsolateral prefrontal cortex (dlFPC). Subjects underwent resting state functional magnetic resonance imaging before and after 20 sessions of high frequency rTMS. Seed voxels identified the affective network (AN; sgACC, amygdala), default mode network (DMN; posterior cingulate cortex [PCC]), and fronto-parietal network (FPN; dlPFC stimulation site).

RESULTS

There was no significant effect of active rTMS over sham on the primary outcome measure (Montgomery-Asberg Depression Scale rating), with both groups improving over time, and no specific effect of rTMS (sham vs active) on connectivity. However, among patients who showed significant improvement, sgACC connectivity decreased for sham (to AN, trend to DMN) and active rTMS responders (to AN, DMN, FPN), but not in non-responders, who tended to maintain connectivity. Including subjects who started with sham but then received open-label active treatment, baseline connectivity from the PCC to the anterior insula was greater in non-responders compared to responders (n = 27, excluding 5 sham responders).

LIMITATIONS

The sample size was small; the stimulation target was non-standard, and the lack of a significant clinical effect of rTMS limits conclusions about negative findings.

CONCLUSIONS

sgACC connectivity reduces along with depressive symptoms, not specific to rTMS therapy. Altered connectivity of DMN with anterior insula may reflect a type of patient less likely to respond to an intervention.

Expectancy Modulation of Opioid Neurotransmission

Expectancies are powerful modulators of cognitive and emotional experiences, as well as the neurobiological responses linked to these processes. In medicine, placebo effects are a clear example of how expectancies activate opioid neurotransmission in a treatment context, leading to the experience of analgesia and the improvement of emotional states, among other symptoms. Molecular neuroimaging techniques using positron emission tomography (PET) and the selective μ-opioid receptor tracer [11C]carfentanil have significantly contributed to our understanding of the neurobiological systems involved in the formation of placebo effects. This line of research has described neural and neurotransmitter networks implicated in placebo effects and provided the technical tools to examine inter-individual differences in the function of placebo responsive mechanisms. As a consequence, the capacity to activate endogenous opioid networks during the administration of placebos has been linked to the concept of resiliency mechanisms, partially determined by genetic factors, and uncovered by the cognitive emotional integration of the expectations created by the therapeutic environment and its maintenance through learning mechanisms. This evidence has contributed to the understanding of the biological bases of the cognitive and psychological mechanisms implicated in the response to treatments, and opened up new opportunities for drug development and the enhancement of treatment responses. Further, delineation of these processes within and across diseases is critical to understand neural systems that could be enhanced to promote symptomatic improvement and modify disease progression.

What Is Minimally Required to Elicit Placebo Effects?

Placebo effects have often been attributed to cognitive processes described as "learning" and/or "expectancy," yet the role of conscious awareness is unclear. Furthermore, little is known about the placebo effects in patients with limited cognitive abilities, such as intellectual disability. Here, recent data on placebo mechanisms in patients with impaired cognitive function will be discussed, as well as experimental studies investigating how implicit cognitive processes may shape placebo effects. Together these studies comment on the minimum requirements in order to elicit placebo effects, both from the view of conscious awareness and from the perspective of Intelligence Quotient and basic brain function. Together with recent conceptualizations of placebo effects in terms of predictive coding, there is evidence to suggest that placebo effects are fundamental responses of the brain that have developed to promote survival.

Pathways to Neuroprediction: Opportunities and challenges to prediction of treatment response in depression

PURPOSE OF REVIEW

We set out to review the current state of science in neuroprediction, using biological measures of brain function, with task based fMRI to prospectively predict response to a variety of treatments.

RECENT FINDINGS

Task-based fMRI neuroprediction studies are balanced between whole brain and ROI specific analyses. The predominant tasks are emotion processing, with ROIs based upon amygdala and subgenual anterior cingulate gyrus, both within the salience and emotion network. A rapidly emerging new area of neuroprediction is of disease course and illness recurrence. Concerns include use of open-label and single arm studies, lack of consideration of placebo effects, unbalanced adjustments for multiple comparisons (over focus on type I error), small sample sizes, unreported effect sizes, overreliance on ROI studies.

SUMMARY

There is a need to adjust neuroprediction study reporting so that greater coherence can facilitate meta analyses, and increased funding for more multiarm studies in neuroprediction.

Network Mechanisms of Clinical Response to Transcranial Magnetic Stimulation in Posttraumatic Stress Disorder and Major Depressive Disorder

BACKGROUND

Repetitive transcranial magnetic stimulation (TMS) therapy can modulate pathological neural network functional connectivity in major depressive disorder (MDD). Posttraumatic stress disorder is often comorbid with MDD, and symptoms of both disorders can be alleviated with TMS therapy. This is the first study to evaluate TMS-associated changes in connectivity in patients with comorbid posttraumatic stress disorder and MDD.

METHODS

Resting-state functional connectivity magnetic resonance imaging was acquired before and after TMS therapy in 33 adult outpatients in a prospective open trial. TMS at 5 Hz was delivered, in up to 40 daily sessions, to the left dorsolateral prefrontal cortex. Analyses used a priori seeds relevant to TMS, posttraumatic stress disorder, or MDD (subgenual anterior cingulate cortex [sgACC], left dorsolateral prefrontal cortex, hippocampus, and basolateral amygdala) to identify imaging predictors of response and to evaluate clinically relevant changes in connectivity after TMS, followed by leave-one-out cross-validation. Imaging results were explored using data-driven multivoxel pattern activation.

RESULTS

More negative pretreatment connectivity between the sgACC and the default mode network predicted clinical improvement, as did more positive amygdala-to-ventromedial prefrontal cortex connectivity. After TMS, symptom reduction was associated with reduced connectivity between the sgACC and the default mode network, left dorsolateral prefrontal cortex, and insula, and reduced connectivity between the hippocampus and the salience network. Multivoxel pattern activation confirmed seed-based predictors and correlates of treatment outcomes.

CONCLUSIONS

These results highlight the central role of the sgACC, default mode network, and salience network as predictors of TMS response and suggest their involvement in mechanisms of action. Furthermore, this work indicates that there may be network-based biomarkers of clinical response relevant to these commonly comorbid disorders.

Attitudes toward placebo-controlled clinical trials among depressed patients in Japan

BACKGROUND

Placebo-controlled clinical trials are the standard in the design of clinical studies for the licensing of new drugs. Medical and ethical concerns regarding placebo use still exist in clinical trials of depressed patients. The aim of this study was to investigate the attitudes toward placebo-controlled clinical trials and to assess factors related to the willingness to participate in such trials among depressed patients in Japan.

METHODS

A total of 206 depressed patients aged 49.5 ± 15.7 years (mean ± SD) who were admitted to three psychiatric hospitals were recruited for a cross-sectional study from June 2015 to March 2016. After a thorough explanation of the placebo, the study participants completed a brief 14-item questionnaire developed to evaluate patients' attitudes regarding possible participation in placebo-controlled clinical trials. The Quick Inventory of Depressive Symptomatology was also administered to assess depressive symptoms.

RESULTS

The results indicated that 47% of the patients would be willing to participate in a placebo-controlled clinical trial. Expectations for the improvement of disease, desire to receive more medical care, encouragement by family or friends, and desire to support the development of new drugs were associated with the willingness to participate in such trials, whereas a belief that additional time would be required for medical examinations and fear of exacerbation of symptoms due to placebo use were associated with non-participation.

LIMITATIONS

Patients were asked about possible participation in placebo-controlled clinical trials.

CONCLUSIONS

Less than half of the respondents were willing to participate in placebo-controlled clinical trials. Attitudes toward participation in a placebo-controlled clinical trial need to be considered when deciding whether to conduct such a trial.

A Novel Strategy to Identify Placebo Responders: Prediction Index of Clinical and Biological Markers in the EMBARC Trial

BACKGROUND

One in three clinical trial patients with major depressive disorder report symptomatic improvement with placebo. Strategies to mitigate the effect of placebo responses have focused on modifying study design with variable success. Identifying and excluding or controlling for individuals with a high likelihood of responding to placebo may improve clinical trial efficiency and avoid unnecessary medication trials.

METHODS

Participants included those assigned to the placebo arm (n = 141) of the Establishing Moderators and Biosignatures for Antidepressant Response in Clinical Care (EMBARC) trial. The elastic net was used to evaluate 283 baseline clinical, behavioral, imaging, and electrophysiological variables to identify the most robust yet parsimonious features that predicted depression severity at the end of the double-blind 8-week trial. Variables retained in at least 50% of the 100 imputed data sets were used in a Bayesian multiple linear regression model to simultaneously predict the probabilities of response and remission.

RESULTS

Lower baseline depression severity, younger age, absence of melancholic features or history of physical abuse, less anxious arousal, less anhedonia, less neuroticism, and higher average theta current density in the rostral anterior cingulate predicted a higher likelihood of improvement with placebo. The Bayesian model predicted remission and response with an actionable degree of accuracy (both AUC > 0.73). An interactive calculator was developed predicting the likelihood of placebo response at the individual level.

CONCLUSION

Easy-to-measure clinical, behavioral, and electrophysiological assessments can be used to identify placebo responders with a high degree of accuracy. Development of this calculator based on these findings can be used to identify potential placebo responders.

New medications for treatment-resistant depression: a brief review of recent developments

There is a great unmet need for new medications with novel mechanisms of action that can effectively treat patients who do not benefit from standard antidepressant therapies. After a period in which it seemed as if the pharmaceutical pipeline for new antidepressants was going dry, the past decade has witnessed renewed interest, beginning with discovery of the antidepressant effects of ketamine. This article briefly highlights more recent research on ketamine and other investigational antidepressants.

Striatal dopamine D2/3 receptor-mediated neurotransmission in major depression: Implications for anhedonia, anxiety and treatment response

Dopamine (DA) neurotransmission within the brain's reward circuit has been implicated in the pathophysiology of depression and in both, cognitive and pharmacological mechanisms of treatment response. Still, a direct relationship between measures of DA neurotransmission and reward-related deficits in patients with depression has not been demonstrated. To gain insight into the symptom-specific alterations in the DA system in patients with depression, we used positron emission tomography (PET) and the D_2/3 receptor-selective radiotracer [¹¹C]raclopride in twenty-three non-smoking un-medicated Major Depressive Disorder (MDD) patients and sixteen healthy controls (HC). We investigated the relationship between D_2/3 receptor availability and baseline measures of depression severity, anxiety, anhedonia, and cognitive and pharmacological mechanisms of treatment response. We found that, compared to controls, patients with depression showed greater D_2/3 receptor availability in several striatal regions, including the bilateral ventral pallidum/nucleus accumbens (vPAL/NAc), and the right ventral caudate and putamen. In the depressed sample, D_2/3 receptor availability in the caudal portion of the ventral striatum (NAc/vPAL) correlated with higher anxiety symptoms, whereas D_2/3 receptor availability in the rostral area of the ventral striatum correlated negatively with the severity of motivational anhedonia. Finally, MDD non-remitters showed greater baseline anxiety, greater D_2/3 availability in the NAc/vPAL, and greater placebo-induced DA release in the bilateral NAc. Our results demonstrate abnormally high D_2/3 receptor availability in the ventral striatum of patients with MDD, which seem to be associated with comorbid anxiety symptoms and lack of response to antidepressants.

An updated synthesis of [11 C]carfentanil for positron emission tomography (PET) imaging of the μ-opioid receptor

[¹¹ C]Carfentanil ([¹¹ C]CFN) is a selective radiotracer for in vivo positron emission tomography imaging studies of the μ-opioid system that, in our laboratories, is synthesized by methylation of the corresponding carboxylate precursor with [¹¹ C]MeOTf, and purified using a C2 solid-phase extraction cartridge. Changes in the commercial availability of common C2 cartridges have necessitated future proofing the synthesis of [¹¹ C]CFN to maintain reliable delivery of the radiotracer for clinical imaging studies. An updated synthesis of [¹¹ C]CFN is reported that replaces a now obsolete purification cartridge with a new commercially available version and also substitutes the organic solvents used in traditional production methods with ethanol.

Placebo-related effects: a meta-narrative review of conceptualization, mechanisms and their relevance in rheumatology

For decades in medicine, the placebo effect has been conceptualized as a subjective psychological effect associated with an inert substance and considered to be a nuisance noise in the assessment of therapeutic effects in clinical trials. However, research on placebo has undergone substantial developments since the mid-1980s in several fields of knowledge (including methodology, psychology and neurosciences) that challenge this traditional view. Using a meta-narrative approach, this review of conceptualizations, determinants, mechanisms and models of placebo effects shows that placebo effects are genuine biopsychosocial phenomena strongly affected by context and factors surrounding the patient and treatments. Psychological experiments and neurobiological and neuroimaging studies have identified various types of placebo responses, driven by different mechanisms (especially but not only expectation and conditioning) and associated with different chemical, structural and functional features. Insights into the mechanisms involved in placebo responses have led to opportunities for ethical enhancements of these mechanisms in clinical practice, notably by improving the patient-doctor interaction and refining the therapeutic ritual. These developments should be carefully considered in rheumatology settings, in which placebo effects are both prevalent and significant, with the potential to improve patient care.

MicroRNAs 146a/b-5 and 425-3p and 24-3p are markers of antidepressant response and regulate MAPK/Wnt-system genes

Antidepressants (ADs) are the most common treatment for major depressive disorder (MDD). However, only ∼30% of patients experience adequate response after a single AD trial, and this variability remains poorly understood. Here, we investigated microRNAs (miRNAs) as biomarkers of AD response using small RNA-sequencing in paired samples from MDD patients enrolled in a large, randomized placebo-controlled trial of duloxetine collected before and 8 weeks after treatment. Our results revealed differential expression of miR-146a-5p, miR-146b-5p, miR-425-3p and miR-24-3p according to treatment response. These results were replicated in two independent clinical trials of MDD, a well-characterized animal model of depression, and post-mortem human brains. Furthermore, using a combination of bioinformatics, mRNA studies and functional in vitro experiments, we showed significant dysregulation of genes involved in MAPK/Wnt signalling pathways. Together, our results indicate that these miRNAs are consistent markers of treatment response and regulators of the MAPK/Wnt systems.

Antidepressant drugs are the most common treatment for depressive episodes but only a fraction of patients experience adequate response. Here the authors find dysregulation of miRNAs in peripheral blood samples from depressed patients after antidepressant treatment, and show that the miRNAs are regulators of psychiatrically relevant signalling pathways.

Brain Mechanisms of the Placebo Effect: An Affective Appraisal Account

Placebos are sham medical treatments. Nonetheless, they can have substantial effects on clinical outcomes. Placebos depend on a person's psychological and brain responses to the treatment context, which influence appraisals of future well-being. Appraisals are flexible cognitive evaluations of the personal meaning of events and situations that can directly impact symptoms and physiology. They also shape associative learning processes by guiding what is learned from experience. Appraisals are supported by a core network of brain regions associated with the default mode network involved in self-generated emotion, self-evaluation, thinking about the future, social cognition, and valuation of rewards and punishment. Placebo treatments for acute pain and a range of clinical conditions engage this same network of regions, suggesting that placebos affect behavior and physiology by changing how a person evaluates their future well-being and the personal significance of their symptoms.

EEG connectivity between the subgenual anterior cingulate and prefrontal cortices in response to antidepressant medication

Antidepressant medication is the most common treatment for major depressive disorder (MDD), however, the precise working mechanism underlying these treatments remains unclear. Recent neuromodulation treatments demonstrate that direct stimulation of the dorsolateral prefrontal cortex (DLPFC), dorsomedial prefrontal cortex (DMPFC), and subgenual anterior cingulate (sgACC) relate to clinical improvement, suggesting connectivity alterations of the DLPFC-DMPFC-sgACC network to mediate antidepressant response. The international Study to Predict Optimized Treatment in Depression (iSPOT-D) is an international multicentre study that collected EEG data for 1008 MDD patients, randomized to 3 different antidepressant medications (N=447 MDD with complete pre- and post-treatment data and N=336 non-MDD). Treatment response was defined by a decline of >50% on the Hamilton Rating Score for Depression (HRSD₁₇). We investigated whether connectivity in alpha and theta frequencies of the DLPFC-DMPFC-sgACC network changed from pre- to post-treatment between: (i) patients and controls, and (ii) responders (R) and non-responders (NR). Women exhibited higher alpha and theta connectivity compared to males, both pre- and post-treatment. Furthermore, theta, but not alpha, hypo-connectivity was found for MDD patients. A decreased alpha connectivity after treatment was found only for male responders, while non-responders and females exhibited no changes in alpha connectivity. Decreasing alpha connectivity could potentially serve as a treatment emergent biomarker, in males only. Furthermore, it could be useful to a priori stratify by gender for future MDD studies.

Experimental medication treatment approaches for depression

Depression is one of the most common psychiatric conditions. Symptoms can lead to significant disability, which result in impairments in overall quality of life. Though there are many approved antidepressant treatments for depression-including selective serotonin reuptake inhibitors, tricyclic antidepressants and monoamine oxidase inhibitors-about a third of patients do not respond to these medications. Therefore, it is imperative for drug discovery to continue towards the development of novel and rapidly acting compounds, especially for patients with treatment-resistant depression. After a brief review of the efficacy of approved antidepressant therapies, we will discuss experimental medication treatments for depression. Specifically, we examine novel medications that are thought to primarily modulate the glutamatergic, cholinergic and opioid systems to achieve antidepressant efficacy. We also give examples of anti-inflammatories, neurokinin-1 modulators, vasopressin antagonists and neurogenesis enhancers that may have a therapeutic role in treatment-resistant depression. The current pipeline of antidepressant treatments is shifting towards medications with novel mechanisms, which may lead to important, life-changing discoveries for patients with severe disease.

Frontal-Brainstem Pathways Mediating Placebo Effects on Social Rejection

Placebo treatments can strongly affect clinical outcomes, but research on how they shape other life experiences and emotional well-being is in its infancy. We used fMRI in humans to examine placebo effects on a particularly impactful life experience, social pain elicited by a recent romantic rejection. We compared these effects with placebo effects on physical (heat) pain, which are thought to depend on pathways connecting prefrontal cortex and periaqueductal gray (PAG). Placebo treatment, compared with control, reduced both social and physical pain, and increased activity in the dorsolateral prefrontal cortex (dlPFC) in both modalities. Placebo further altered the relationship between affect and both dlPFC and PAG activity during social pain, and effects on behavior were mediated by a pathway connecting dlPFC to the PAG, building on recent work implicating opioidergic PAG activity in the regulation of social pain. These findings suggest that placebo treatments reduce emotional distress by altering affective representations in frontal-brainstem systems.SIGNIFICANCE STATEMENT Placebo effects are improvements due to expectations and the socio-medical context in which treatment takes place. Whereas they have been extensively studied in the context of somatic conditions such as pain, much less is known of how treatment expectations shape the emotional experience of other important stressors and life events. Here, we use brain imaging to show that placebo treatment reduces the painful feelings associated with a recent romantic rejection by recruiting a prefrontal-brainstem network and by shifting the relationship between brain activity and affect. Our findings suggest that this brain network may be important for nonspecific treatment effects across a wide range of therapeutic approaches and mental health conditions.

Endogenous Opiates and Behavior: 2015

This paper is the thirty-eighth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2015 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.

A Review of the Theoretical and Biological Understanding of the Nocebo and Placebo Phenomena

PURPOSE

Placebos are commonly used in experimental and patient populations and are known to influence treatment outcomes. The mechanism of action of placebos has been investigated by several researchers. This review investigates the current knowledge regarding the theoretical and biological underpinning of the nocebo and placebo phenomena.

METHOD

Literature was searched using PubMed using the following keywords: nocebo, placebo, μ-opioid, dopamine, conditioning, and expectancy. Relevant papers were selected for review by the authors.

FINDINGS

The roles of conditioning and expectancy, and characteristics associated with nocebo and placebo responses, are discussed. These factors affect nocebo and placebo responses, although their effect sizes vary greatly, depending on inter-individual differences and different experimental paradigms. The neurobiology of the nocebo and placebo phenomena is also reviewed, emphasizing the involvement of reward pathways, such as the μ-opioid and dopamine pathways. Neurobiological pathways have been investigated in a limited range of experimental paradigms, with the greatest efforts on experimental models of placebo analgesia. The interconnectedness of psychological and physiological drivers of nocebo and placebo responses is a core feature of these phenomena.

IMPLICATIONS

Further research is needed to fully understand the underpinnings of the nocebo and placebo phenomena. Neurobiology pathways need to be investigated in experimental paradigms that model the placebo response to a broader range of pathologies. Similarly, although many psychological factors and inter-individual characteristics have been identified as significant mediators and moderators of nocebo and placebo responses, the factors identified to date are unlikely to be exhaustive.

Nicotine-specific and non-specific effects of cigarette smoking on endogenous opioid mechanisms

This study investigates differences in μ-opioid receptor mediated neurotransmission in healthy controls and overnight-abstinent smokers, and potential effects of the OPRM1 A118G genotype. It also examines the effects of smoking denicotinized (DN) and average nicotine (N) cigarettes on the μ-opioid system. Positron emission tomography with (11)C-carfentanil was used to determine regional brain μ-opioid receptor (MOR) availability (non-displaceable binding potential, BPND) in a sample of 19 male smokers and 22 nonsmoking control subjects. Nonsmokers showed greater MOR BPND than overnight abstinent smokers in the basal ganglia and thalamus. BPND in the basal ganglia was negatively correlated with baseline craving levels and Fagerström scores. Interactions between group and genotype were seen in the nucleus accumbens bilaterally and the amygdala, with G-allele carriers demonstrating lower BPND in these regions, but only among smokers. After smoking the DN cigarette, smokers showed evidence of MOR activation in the thalamus and nucleus accumbens. No additional activation was observed after the N cigarette, with a mean effect of increases in MOR BPND (i.e., deactivation) with respect to the DN cigarette effects in the thalamus and left amygdala. Changes in MOR BPND were related to both Fagerström scores and changes in craving. This study showed that overnight-abstinent smokers have lower concentrations of available MORs than controls, an effect that was related to both craving and the severity of addiction. It also suggests that nicotine non-specific elements of the smoking experience have an important role in regulating MOR-mediated neurotransmission, and in turn modulating withdrawal-induced craving ratings.

Psychosomatic problems in dentistry

Many dental patients complain of oral symptoms after dental treatment, such as chronic pain or occlusal discomfort, for which the cause remains undetermined. These symptoms are often thought to be mental or emotional in origin, and patients are considered to have an "oral psychosomatic disorder". Representative medically unexplained oral symptoms/syndromes (MUOS) include burning mouth syndrome, atypical odontalgia, phantom bite syndrome, oral cenesthopathy, or halitophobia. With an increasing prevalence of these MUOS, dentists are being asked to develop new approaches to dental treatment, which include taking care of not only the patient's teeth but also the patient's suffering. Progress in the understanding of mind-body interactions will lead to investigations on the pathophysiology of MUOS and the development of new therapeutic approaches.

Affective preclinical modeling of psychiatric disorders: taking imbalanced primal emotional feelings of animals seriously in our search for novel antidepressants

Preclinical animal models of psychiatric disorders are of critical importance for advances in development of new psychiatric medicine. Regrettably, behavior-only models have yielded no novel targeted treatments during the past half-century of vigorous deployment. This may reflect the general neglect of experiential aspects of animal emotions, since affective mental states of animals supposedly cannot be empirically monitored. This supposition is wrong—to the extent that the rewarding and punishing aspects of emotion circuit arousals reflect positive and negative affective states. During the past decade, the use of such affective neuroscience-based animal modeling has yielded three novel antidepressants (i) via the alleviation of psychic pain with low doses of buprenorphine; (ii) via the amplification of enthusiasm by direct stimulation of the medial forebrain bundle); and (iii) via the facilitation of the capacity for social joy with play facilitators such as rapastinel (GLYX13). All have progressed to successful human testing. For optimal progress, it may be useful for preclinical investigators to focus on the evolved affective foundations of psychiatrically relevant brain emotional disorders for optimal animal modeling.

Salience Network Functional Connectivity Predicts Placebo Effects in Major Depression

BACKGROUND

Recent neuroimaging studies have demonstrated resting-state functional connectivity (rsFC) abnormalities among intrinsic brain networks in Major Depressive Disorder (MDD); however, their role as predictors of treatment response has not yet been explored. Here, we investigate whether network-based rsFC predicts antidepressant and placebo effects in MDD.

METHODS

We performed a randomized controlled trial of two weeklong, identical placebos (described as having either "active" fast-acting, antidepressant effects or as "inactive") followed by a ten-week open-label antidepressant medication treatment. Twenty-nine participants underwent a rsFC fMRI scan at the completion of each placebo condition. Networks were isolated from resting-state blood-oxygen-level-dependent signal fluctuations using independent component analysis. Baseline and placebo-induced changes in rsFC within the default-mode, salience, and executive networks were examined for associations with placebo and antidepressant treatment response.

RESULTS

Increased baseline rsFC in the rostral anterior cingulate (rACC) within the salience network, a region classically implicated in the formation of placebo analgesia and the prediction of treatment response in MDD, was associated with greater response to one week of active placebo and ten weeks of antidepressant treatment. Machine learning further demonstrated that increased salience network rsFC, mainly within the rACC, significantly predicts individual responses to placebo administration.

CONCLUSIONS

These data demonstrate that baseline rsFC within the salience network is linked to clinical placebo responses. This information could be employed to identify patients who would benefit from lower doses of antidepressant medication or non-pharmacological approaches, or to develop biomarkers of placebo effects in clinical trials.

Affective preclinical modeling of psychiatric disorders: taking imbalanced primal emotional feelings of animals seriously in our search for novel antidepressants

Preclinical animal models of psychiatric disorders are of critical importance for advances in development of new psychiatric medicine. Regrettably, behavior-only models have yielded no novel targeted treatments during the past half-century of vigorous deployment. This may reflect the general neglect of experiential aspects of animal emotions, since affective mental states of animals supposedly cannot be empirically monitored. This supposition is wrong-to the extent that the rewarding and punishing aspects of emotion circuit arousals reflect positive and negative affective states. During the past decade, the use of such affective neuroscience-based animal modeling has yielded three novel antidepressants (i) via the alleviation of psychic pain with low doses of buprenorphine; (ii) via the amplification of enthusiasm by direct stimulation of the medial forebrain bundle); and (iii) via the facilitation of the capacity for social joy with play facilitators such as rapastinel (GLYX13). All have progressed to successful human testing. For optimal progress, it may be useful for preclinical investigators to focus on the evolved affective foundations of psychiatrically relevant brain emotional disorders for optimal animal modeling.