A link between serotonin-related gene polymorphisms, amygdala activity, and placebo-induced relief from social anxiety

'Oxytocin' for the outwardly oriented: Evidence for interactive effects in placebo responding

OBJECTIVE

In order to harness the placebo effect for clinical benefit, more research is needed to determine who might be responsive to a placebo treatment. Recently, a two-faceted Transactional Model of Placebo Responding (TMPR) was offered, which suggests different personality types might respond to different contextual cues. The current study directly tested this model by manipulating treatment descriptors to match the two purported facets of responsiveness.

METHODS

Physically healthy volunteers (N=77) experiencing life stress were randomised to either the: (1) wait-list control, (2) 'serotonin treatment' group; or (3) 'oxytocin treatment' group. Both treatment groups received an 'antistress' intranasal spray (placebo). The 'serotonin' and 'oxytocin' treatments were described to appeal to the two purported facets responsiveness set out in the TMPR, inward and outward orientation. The BIS/BAS scale was used as proxies for inward (BIS) and outward (BAS) orientation. It was hypothesised that high BAS types would be more responsive to the 'oxytocin' and high BIS types would be more responsive to the 'serotonin'.

RESULTS

Findings provide partial support for hypotheses, with high but not low BAS types having a greater response to the 'oxytocin' placebo; but the pattern of responses from high BIS types were contrary to predictions.

CONCLUSIONS

Findings indicate interactions between personality type and environmental cues may contribute to placebo responding, but more research is needed to investigate possible operationalisations of responsiveness and the contextual cues to which different types may respond.

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.

Neuro-Bio-Behavioral Mechanisms of Placebo and Nocebo Responses: Implications for Clinical Trials and Clinical Practice

The placebo effect has often been considered a nuisance in basic and particularly clinical research. This view has gradually changed in recent years due to deeper insight into the neuro-bio-behavioral mechanisms steering both the placebo and nocebo responses, the evil twin of placebo. For the neuroscientist, placebo and nocebo responses have evolved as indispensable tools to understand brain mechanisms that link cognitive and emotional factors with symptom perception as well as peripheral physiologic systems and end organ functioning. For the clinical investigator, better understanding of the mechanisms driving placebo and nocebo responses allow the control of these responses and thereby help to more precisely define the efficacy of a specific pharmacological intervention. Finally, in the clinical context, the systematic exploitation of these mechanisms will help to maximize placebo responses and minimize nocebo responses for the patient's benefit. In this review, we summarize and critically examine the neuro-bio-behavioral mechanisms underlying placebo and nocebo responses that are currently known in terms of different diseases and physiologic systems. We subsequently elaborate on the consequences of this knowledge for pharmacological treatments of patients and the implications for pharmacological research, the training of healthcare professionals, and for the health care system and future research strategies on placebo and nocebo responses.

Placebo analgesia: understanding the mechanisms

Expectations of pain relief drive placebo analgesia. Understanding how expectations of improvement trigger distinct biological systems to shape therapeutic analgesic outcomes has been the focus of recent pharmacologic and neuroimaging studies in the field of pain. Recent findings indicate that placebo effects can imitate the actions of real painkillers and promote the endogenous release of opioids and nonopioids in humans. Social support and observational learning also contribute to placebo analgesic effects. Distinct psychological traits can modulate expectations of analgesia, which facilitate brain pain control mechanisms involved in pain reduction. Many studies have highlighted the importance and clinical relevance of these responses. Gaining deeper understanding of these pain modulatory mechanisms has important implications for personalizing patient pain management.

Age and sex as moderators of the placebo response – an evaluation of systematic reviews and meta-analyses across medicine

Predictors of the placebo response (PR) in randomized controlled trials (RCT) have been searched for ever since RCT have become the standard for testing novel therapies and age and gender are routinely documented data in all trials irrespective of the drug tested, its indication, and the primary and secondary end points chosen. To evaluate whether age and gender have been found to be reliable predictors of the PR across medical subspecialties, we extracted 75 systematic reviews, meta-analyses, and meta-regressions performed in major medical areas (neurology, psychiatry, internal medicine) known for high PR rates. The literature database used contains approximately 2,500 papers on various aspects of the genuine PR. These ‘meta-analyses’ were screened for statistical predictors of the PR across multiple RCT, including age and gender, but also other patient-based and design-based predictors of higher PR rates. Retrieved papers were sorted for areas and disease categories. Only 15 of the 75 analyses noted an effect of younger age to be associated with higher PR, and this was predominantly in psychiatric conditions but not in depression, and internal medicine but not in gastroenterology. Female gender was associated with higher PR in only 3 analyses. Among the patient-based predictors, the most frequently noted factor was lower symptom severity at baseline, and among the design- based factors, it was a randomization ratio that selected more patients to drugs than to placebo, more frequent study visits, and more recent trials that were associated with higher PR rates. While younger age may contribute to the PR in some conditions, sex does not. There is currently no evidence that the PR is different in the elderly. PR are, however, markedly influenced by the symptom severity at baseline, and by the likelihood of receiving active treatment in placebo- controlled trials.

Rethinking psychopharmacotherapy: The role of treatment context and brain plasticity in antidepressant and antipsychotic interventions

Emerging evidence indicates that treatment context profoundly affects psychopharmacological interventions. We review the evidence for the interaction between drug application and the context in which the drug is given both in human and animal research. We found evidence for this interaction in the placebo response in clinical trials, in our evolving knowledge of pharmacological and environmental effects on neural plasticity, and in animal studies analyzing environmental influences on psychotropic drug effects. Experimental placebo research has revealed neurobiological trajectories of mechanisms such as patients' treatment expectations and prior treatment experiences. Animal research confirmed that "enriched environments" support positive drug effects, while unfavorable environments (low sensory stimulation, low rates of social contacts) can even reverse the intended treatment outcome. Finally we provide recommendations for context conditions under which psychotropic drugs should be applied. Drug action should be steered by positive expectations, physical activity, and helpful social and physical environmental stimulation. Future drug trials should focus on fully controlling and optimizing such drug×environment interactions to improve trial sensitivity and treatment outcome.

The placebo effect: From concepts to genes

Despite its initial treatment as a nuisance variable, the placebo effect is now recognized as a powerful determinant of health across many different diseases and encounters. This is in light of some remarkable findings ranging from demonstrations that the placebo effect significantly modulates the response to active treatments in conditions such as pain, anxiety, Parkinson's disease, and some surgical procedures. Here, we review pioneering studies and recent advances in behavioral, neurobiological, and genetic influences on the placebo effect. Consistent with recent conceptualizations, the placebo effect is presented as the product of a general expectancy learning mechanism in which verbal, conditioned, and social cues are centrally integrated to change behaviors and outcomes. Examples of the integration of verbal and conditioned cues, such as instructed reversal of placebo effects are also incorporated into this model. We discuss neuroimaging studies that have identified key brain regions and modulatory mechanisms underlying placebo effects using well-established behavioral paradigms. Finally, we present a synthesis of recent genetics studies on the placebo effect, highlighting a promising link between genetic variants in the dopamine, opioid, serotonin, and endocannabinoid pathways and placebo responsiveness. Greater understanding of the behavioral, neurobiological, and genetic influences on the placebo effect is critical for evaluating medical interventions and may allow health professionals to tailor and personalize interventions in order to maximize treatment outcomes in clinical settings.

Regional Homogeneity of Resting-State Brain Activity Suppresses the Effect of Dopamine-Related Genes on Sensory Processing Sensitivity

Sensory processing sensitivity (SPS) is an intrinsic personality trait whose genetic and neural bases have recently been studied. The current study used a neural mediation model to explore whether resting-state brain functions mediated the effects of dopamine-related genes on SPS. 298 healthy Chinese college students (96 males, mean age = 20.42 years, SD = 0.89) were scanned with magnetic resonance imaging during resting state, genotyped for 98 loci within the dopamine system, and administered the Highly Sensitive Person Scale. We extracted a “gene score” that summarized the genetic variations representing the 10 loci that were significantly linked to SPS, and then used path analysis to search for brain regions whose resting-state data would help explain the gene-behavior association. Mediation analysis revealed that temporal homogeneity of regional spontaneous activity (ReHo) in the precuneus actually suppressed the effect of dopamine-related genes on SPS. The path model explained 16% of the variance of SPS. This study represents the first attempt at using a multi-gene voxel-based neural mediation model to explore the complex relations among genes, brain, and personality.

Placebo Responses in Genetically Determined Intellectual Disability: A Meta-Analysis

Background

Genetically determined Intellectual Disability (ID) is an intractable condition that involves severe impairment of mental abilities such as learning, reasoning and predicting the future. As of today, little is known about the placebo response in patients with ID.

Objective

To determine if placebo response exists in patients with genetically determined ID.

Data sources and Study selection

We searched Medline/PubMed, EMBASE, CENTRAL and PsycINFO to find all placebo-controlled double-blind randomized clinical trials (RCTs) in patients with genetically determined ID, published up to April 2013, focusing on core ID symptoms.

Data extraction and synthesis

Two investigators extracted outcome data independently.

Main outcomes and measures

Bias-corrected standardized mean difference (Hedge’s g) was computed for each outcome measure, using the Comprehensive Meta-Analysis software. A priori defined patient sub-groups were analyzed using a mixed-effect model. The relationship between pre-defined continuous variable moderators (age, IQ, year of publication and trial duration) and effect size was analyzed using meta-regression

Results

Twenty-two placebo-controlled double-blind RCTs met the inclusion criteria (n = 721, mean age = 17.1 years, 62% men, mean trial duration = 35 weeks). There was a significant overall placebo response from pre- to post-treatment in patients with ID (g = 0.468, p = 0.002), both for “subjective outcomes” (a third-person’s evaluation of the patient) (g = 0.563, p = 0.022) and “objective outcomes” (direct evaluation of the patient’s abilities) (g = 0.434, p = 0.036). Individuals with higher IQ had higher response to placebo (p = 0.02) and no placebo response was observed in ID patients with comorbid dementia. A significant effect of age (p = 0.02) was found, indicating higher placebo responses in treatment of younger patients.

Conclusions and relevance

Results suggest that patients with genetically determined ID improve in the placebo arm of RCTs. Several mechanisms may contribute to placebo effects in ID, including expectancy, implicit learning and “placebo-by-proxy” induced by clinicians/family members. As the condition is refractory, there is little risk that improvements are explained by spontaneous remission. While new avenues for treatment of genetically determined ID are emerging, our results demonstrate how contextual factors can affect clinical outcomes and emphasize the importance of being vigilant on the role of placebos when testing novel treatments in ID.

Neural mechanisms of placebo anxiolysis

The beneficial effects of placebo treatments on fear and anxiety (placebo anxiolysis) are well known from clinical practice, and there is strong evidence indicating a contribution of treatment expectations to the efficacy of anxiolytic drugs. Although clinically highly relevant, the neural mechanisms underlying placebo anxiolysis are poorly understood. In two studies in humans, we tested whether the administration of an inactive treatment along with verbal suggestions of anxiolysis can attenuate experimentally induced states of phasic fear and/or sustained anxiety. Phasic fear is the response to a well defined threat and includes attentional focusing on the source of threat and concomitant phasic increases of autonomic arousal, whereas in sustained states of anxiety potential and unclear danger requires vigilant scanning of the environment and elevated tonic arousal levels. Our placebo manipulation consistently reduced vigilance measured in terms of undifferentiated reactivity to salient cues (indexed by subjective ratings, skin conductance responses and EEG event-related potentials) and tonic arousal [indexed by cue-unrelated skin conductance levels and enhanced EEG alpha (8-12 Hz) activity], indicating a downregulation of sustained anxiety rather than phasic fear. We also observed a placebo-dependent sustained increase of frontal midline EEG theta (4-7 Hz) power and frontoposterior theta coupling, suggesting the recruitment of frontally based cognitive control functions. Our results thus support the crucial role of treatment expectations in placebo anxiolysis and provide insight into the underlying neural mechanisms.

Influence of a Suggestive Placebo Intervention on Psychobiological Responses to Social Stress: A Randomized Controlled Trial

We tested the hypothesis that a suggestive placebo intervention can reduce the subjective and neurobiological stress response to psychosocial stress. Fifty-four healthy male subjects with elevated levels of trait anxiety were randomly assigned in a 4:4:1 fashion to receive either no treatment (n = 24), a placebo pill (n = 24), or a herbal drug (n = 6) before undergoing a stress test. We repeatedly measured psychological variables as well as salivary cortisol, alpha-amylase, and heart rate variability prior to and following the stress test. The stressor increased subjective stress and anxiety, salivary cortisol, and alpha-amylase, and decreased heart rate variability (all P < .001). However, no significant differences between subjects receiving placebo or no treatment were found. Subjects receiving placebo showed increased wakefulness during the stress test compared with no-treatment controls (P < .001). Thus, the suggestive placebo intervention increased alertness, but modulated neither subjective stress and anxiety nor the physiological response to psychosocial stress.

Genetics and the placebo effect: the placebome

Placebos are indispensable controls in randomized clinical trials (RCTs), and placebo responses significantly contribute to routine clinical outcomes. Recent neurophysiological studies reveal neurotransmitter pathways that mediate placebo effects. Evidence that genetic variations in these pathways can modify placebo effects raises the possibility of using genetic screening to identify placebo responders and thereby increase RCT efficacy and improve therapeutic care. Furthermore, the possibility of interaction between placebo and drug molecular pathways warrants consideration in RCT design. The study of genomic effects on placebo response, 'the placebome', is in its infancy. Here, we review evidence from placebo studies and RCTs to identify putative genes in the placebome, examine evidence for placebo-drug interactions, and discuss implications for RCTs and clinical care.

Placebo eff ects in psychiatry: mediators and moderators

A strong placebo response in psychiatric disorders has been noted for the past 50 years and various attempts have been made to identify predictors of it, by use of meta-analyses of randomised controlled trials and laboratory studies. We reviewed 31 meta-analyses and systematic reviews of more than 500 randomised placebo-controlled trials across psychiatry (depression, schizophrenia, mania, attention-deficit hyperactivity disorder, autism, psychosis, binge-eating disorder, and addiction) for factors identified to be associated with increased placebo response. Of 20 factors discussed, only three were often linked to high placebo responses: low baseline severity of symptoms, more recent trials, and unbalanced randomisation (more patients randomly assigned to drug than placebo). Randomised controlled trials in non-drug therapy have not added further predictors, and laboratory studies with psychological, brain, and genetic approaches have not been successful in identifying predictors of placebo responses. This comprehensive Review suggests that predictors of the placebo response are still to be discovered, the response probably has more than one mediator, and that different and distinct moderators are probably what cause the placebo response within psychiatry and beyond.

Understanding placebo and nocebo responses for pain management

Placebo analgesia makes individuals experience relief of their pain simply by virtue of the anticipation of a benefit. A reduction of pain can occur also when placebos follow the administration of active and effective painkillers. In fact, studies indicate that placebos mimic the action of active treatments and promote the endogenous release of opioids in both humans and animals. Finally, social support and observational learning also lead to analgesic effects. Thus, different psychological factors and situations induce expectations of analgesia facilitating the activation of the top-down systems for pain control along with the release of endogenous mediators crucially involved in placebo-induced benefits. Recent scientific investigation in the field of brain imaging is opening new avenues to understanding the cognitive mechanisms and neurobiological substrates of expectation-induced pain modulation. Gaining deeper knowledge of top-down mechanisms of pain modulation has enormous implications for personalizing and optimizing pain management.

Of 'disgrace' and 'pain'--corticolimbic interaction patterns for disorder-relevant and emotional words in social phobia

Limbic hyperactivation and an impaired functional interplay between the amygdala and the prefrontal cortex are discussed to go along with, or even cause, pathological anxiety. Within the multi-faceted group of anxiety disorders, the highly prevalent social phobia (SP) is characterized by excessive fear of being negatively evaluated. Although there is widespread evidence for amygdala hypersensitivity to emotional faces in SP, verbal material has rarely been used in imaging studies, in particular with an eye on disorder-specificity. Using functional magnetic resonance imaging (fMRI) and a block design consisting of (1) overall negative, (2) social-phobia related, (3) positive, and (4) neutral words, we studied 25 female patients with social phobia and 25 healthy female control subjects (HC). Results demonstrated amygdala hyperactivation to disorder-relevant but not to generally negative words in SP patients, with a positive correlation to symptom severity. A functional connectivity analysis revealed a weaker coupling between the amygdala and the left middle frontal gyrus in patients. Symptom severity was negatively related to connectivity strength between the amygdala and the ventromedial prefrontal and orbitofrontal cortex (Brodmann Area 10 and 11). The findings clearly support the view of a hypersensitive threat-detection system, combined with disorder-related alterations in amygdala-prefrontal cortex connectivity in pathological anxiety.

Placebo effects: from the neurobiological paradigm to translational implications

Today we are witnessing a new science of placebo, a complex discipline that encompasses several experimental approaches and translational implications. Modern neurobiological tools have been used to answer important questions in placebo research, such as the top-down modulation of sensory and motor systems as well as the influence of cognition, emotions, and learning on symptoms, diseases, and responses to treatments. What we have learned is that there is not one single placebo effect, but many. This review highlights the translational implications of this new knowledge, ranging from clinical trial design to medical practice to social and ethical issues.

Toward the application of functional neuroimaging to individualized treatment for anxiety and depression

Functional neuroimaging has led to significant gains in understanding the biological bases of anxiety and depressive disorders. However, the ability of functional neuroimaging to directly impact clinical practice is unclear. One important method by which neuroimaging could impact clinical care is to generate single patient level predictions that can guide clinical decision-making. The present review summarizes published functional neuroimaging studies of predictors of medication or psychotherapy outcome in major depressive disorder, obsessive-compulsive disorder (OCD), posttraumatic stress disorder, generalized anxiety disorder, panic disorder, and social anxiety disorder. In major depressive disorder and OCD, there is converging evidence of specific brain circuitry that has both been implicated in the disordered state itself, and where pretreatment activation levels have been predictive of treatment response. Specifically, in major depressive disorder, greater pretreatment ventral and pregenual anterior cingulate cortex (ACC) activation may predict better antidepressant medication outcome but poorer psychotherapy outcome. In OCD, activation in the ACC and orbitofrontal cortex has been inversely associated with pharmacological treatment response. In other anxiety disorders, research in this area is just beginning, with the ACC potentially implicated. However, the question of whether these results can directly translate to clinical practice remains open. In order to achieve the goal of single patient level prediction and individualized treatment, future research should strive to establish replicable models with good predictive performance and clear incremental validity.

Catechol-O-methyltransferase Val158Met polymorphism is associated with somatosensory amplification and nocebo responses

A large number of unwanted adverse events and symptoms reported by patients in clinical trials are not caused by the drug provided, since most of adverse events also occur in corresponding placebo groups. These nocebo effects also play a major role in drug discontinuation in clinical practice, negatively affecting treatment efficacy as well as patient adherence and compliance. Experimental and clinical data document a large interindividual variability in nocebo responses, however, data on psychological, biological or genetic predictors of nocebo responses are lacking. Thus, with an established paradigm of behaviorally conditioned immunosuppressive effects we analyzed possible genetic predictors for nocebo responses. We focused on the genetic polymorphisms in the catechol-O-methyltransferase (COMT) gene (Val158Met) and analyzed drug specific and general side effects before and after immunosuppressive medication and subsequent placebo intake in 62 healthy male subjects. Significantly more drug-specific as well as general side effects were reported from homozygous carriers of the Val158 variant during medication as well as placebo treatment compared to the other genotype groups. Val158/Val158 carriers also had significantly higher scores in the somatosensory amplification scale (SSAS) and the BMQ (beliefs about medicine questionnaire). Together these data demonstrate potential genetic and psychological variables predicting nocebo responses after drug and placebo intake, which might be utilized to minimize nocebo effects in clinical trials and medical practice.

Amygdala-frontal couplings characterizing SSRI and placebo response in social anxiety disorder

In patients with social anxiety disorder (SAD) it has been reported that selective serotonin reuptake inhibitors (SSRIs) and placebo induce anxiolytic effects by attenuating neural activity in overlapping amygdala subregions, i.e. left basolateral and right ventrolateral amygdala. However, it is not known whether these treatments inhibit amygdala subregions via similar or distinct brain pathways. As anxiolytic treatments may alter amygdala-frontal couplings we investigated differences and similarities in amygdala-frontal functional co-activation patterns between responders and nonresponders to SSRIs and placebo in patients with SAD. Positron emission tomography (PET) with oxygen-15-labeled water was used to measure anxiety-related regional cerebral blood flow in 72 patients with SAD before and after 6-8 wk of treatment under double-blind conditions. Functional couplings were evaluated with a seed region approach using voxel values from the left basolateral and right ventrolateral amygdala. Responders and nonresponders to SSRIs and placebo showed different treatment-induced co-activations between the left amygdala and the dorsolateral prefrontal cortex (dlPFC) as well as the rostral anterior cingulate cortex (ACC). Conjunction analysis suggested shared anxiolysis-dependent inverse co-activations in SSRI and placebo responders between the left amygdala-dlPFC and left amygdala-rostral ACC, and a shared positive co-activation between left amygdala-dorsal ACC. We demonstrate that amygdala-frontal co-activation patterns differentiate effective from ineffective anxiolytic treatments and that SSRI and placebo responders share overlapping neuromodulatory paths that may underlie improved emotion regulation and reduced expression of anxiety.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00343707.

A brain network response to sham surgery

Evaluation of potential therapies for neurological disease has been challenging due to beneficial responses in patients receiving the sham/placebo treatment. Placebo effects are especially prominent in Parkinson's disease (PD), which has become a useful model for studying the neurobiology of placebo responses. In this issue of the JCI, Ko and colleagues identify a neural circuit associated with the placebo response in a PD patient cohort. The observed placebo effect-associated pattern involved metabolic activity increases that corresponded with long-term motor improvements after sham surgery. Presurgery activity in this network was inversely related to sham response, suggesting that this network has potential for identifying sham responders and thus reducing placebo-related variance in surgical trials.

Network modulation following sham surgery in Parkinson's disease

Patient responses to placebo and sham effects are a major obstacle to the development of therapies for brain disorders, including Parkinson's disease (PD). Here, we used functional brain imaging and network analysis to study the circuitry underlying placebo effects in PD subjects randomized to sham surgery as part of a double-blind gene therapy trial. Metabolic imaging was performed prior to randomization, then again at 6 and 12 months after sham surgery. In this cohort, the sham response was associated with the expression of a distinct cerebello-limbic circuit. The expression of this network increased consistently in patients blinded to treatment and correlated with independent clinical ratings. Once patients were unblinded, network expression declined toward baseline levels. Analogous network alterations were not seen with open-label levodopa treatment or during disease progression. Furthermore, sham outcomes in blinded patients correlated with baseline network expression, suggesting the potential use of this quantitative measure to identify "sham-susceptible" subjects before randomization. Indeed, Monte Carlo simulations revealed that a priori exclusion of such individuals substantially lowers the number of randomized participants needed to demonstrate treatment efficacy. Individualized subject selection based on a predetermined network criterion may therefore limit the need for sham interventions in future clinical trials.

Are all placebo respondents non-smokers?

BACKGROUND

In smoking cessation trials, placebo response rates are reported to be rather low, and they are lowest when compared to the placebo response rates of treatment of other addictions. We hypothesized that high placebo response rates in trials outside of cessation treatment may predict low participation of smokers, and that non-smoking may be a behavioral marker of the placebo response.

METHODS

We re-analyzed raw data from a randomized controlled drug trial in functional dyspepsia (n=315) for the number of smokers and non-smokers in both treatment arms (drug, placebo) and varied the responder definition in a sensitivity analysis.

RESULTS

An equal number of smokers and non-smokers were assigned to drug and placebo. With the pre-defined responder definition (40% symptom improvement of a patient-reported outcome scale), 3% of placebo responders were smokers, but around 20% of patients among the placebo non-responder, and the drug responders and non-responders. With a more restrictive response definition (50% improvement) none of the placebo responders (n=29) was a smoker while the percentage of smokers remained similar in all other groups (p<.001). Age and gender did not affect this distribution.

CONCLUSION

Non-smoking behavior may be association with higher placebo response rates and may indicate a biomarker for reward sensitivity of the nicotine-dopamine pathway. Common genotypes may underlie both behaviors.

Area-dependent time courses of brain activation during video-induced symptom provocation in social anxiety disorder

BACKGROUND

Previous functional imaging studies using symptom provocation in patients with social anxiety disorder (SAD) reported inconsistent findings, which might be at least partially related to different time-dependent activation profiles in different brain areas. In the present functional magnetic resonance imaging study, we used a novel video-based symptom provocation design in order to investigate the magnitude and time course of activation in different brain areas in 20 SAD patients and 20 healthy controls.

RESULTS

The disorder-related videos induced increased anxiety in patients with SAD as compared to healthy controls. Analyses of brain activation to disorder-related versus neutral video clips revealed amygdala activation during the first but not during the second half of the clips in patients as compared to controls. In contrast, the activation in the insula showed a reversed pattern with increased activation during the second but not during the first half of the video clips. Furthermore, a cluster in the anterior dorsal anterior cingulate cortex showed a sustained response for the entire duration of the videos.

CONCLUSIONS

The present findings suggest that different regions of the fear network show differential temporal response patterns during video-induced symptom provocation in SAD. While the amygdala is involved during initial threat processing, the insula seems to be more involved during subsequent anxiety responses. In accordance with cognitive models of SAD, a medial prefrontal region engaged in emotional-cognitive interactions is generally hyperactivated.

Genetic polymorphisms in monoamine systems and outcome of cognitive behavior therapy for social anxiety disorder

Objective

The role of genetics for predicting the response to cognitive behavior therapy (CBT) for social anxiety disorder (SAD) has only been studied in one previous investigation. The serotonin transporter (5-HTTLPR), the catechol-o-methyltransferase (COMT) val158met, and the tryptophan hydroxylase-2 (TPH2) G-703Tpolymorphisms are implicated in the regulation of amygdala reactivity and fear extinction and therefore might be of relevance for CBT outcome. The aim of the present study was to investigate if these three gene variants predicted response to CBT in a large sample of SAD patients.

Method

Participants were recruited from two separate randomized controlled CBT trials (trial 1: n = 112, trial 2: n = 202). Genotyping were performed on DNA extracted from blood or saliva samples. Effects were analyzed at follow-up (6 or 12 months after treatment) for both groups and for each group separately at post-treatment. The main outcome measure was the Liebowitz Social Anxiety Scale Self-Report.

Results

At long-term follow-up, there was no effect of any genotype, or gene × gene interactions, on treatment response. In the subsamples, there was time by genotype interaction effects indicating an influence of the TPH2 G-703T-polymorphism on CBT short-term response, however the direction of the effect was not consistent across trials.

Conclusions

None of the three gene variants, 5-HTTLPR, COMTval158met and TPH2 G-703T, was associated with long-term response to CBT for SAD.

Trial Registration

ClinicalTrials.gov (ID-NCT0056496)

Population disparities in mental health: insights from cultural neuroscience

By 2050, nearly 1 in 5 Americans (19%) will be an immigrant, including Hispanics, Blacks, and Asians, compared to the 1 in 8 (12%) in 2005. They will vary in the extent to which they are at risk for mental health disorders. Given this increase in cultural diversity within the United States and costly population health disparities across cultural groups, it is essential to develop a more comprehensive understanding of how culture affects basic psychological and biological mechanisms. We examine these basic mechanisms that underlie population disparities in mental health through cultural neuroscience. We discuss the challenges to and opportunities for cultural neuroscience research to determine sociocultural and biological factors that confer risk for and resilience to mental health disorders across the globe.

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.

Placebo and the new physiology of the doctor-patient relationship

Modern medicine has progressed in parallel with the advancement of biochemistry, anatomy, and physiology. By using the tools of modern medicine, the physician today can treat and prevent a number of diseases through pharmacology, genetics, and physical interventions. Besides this materia medica, the patient's mind, cognitions, and emotions play a central part as well in any therapeutic outcome, as investigated by disciplines such as psychoneuroendocrinoimmunology. This review describes recent findings that give scientific evidence to the old tenet that patients must be both cured and cared for. In fact, we are today in a good position to investigate complex psychological factors, like placebo effects and the doctor-patient relationship, by using a physiological and neuroscientific approach. These intricate psychological factors can be approached through biochemistry, anatomy, and physiology, thus eliminating the old dichotomy between biology and psychology. This is both a biomedical and a philosophical enterprise that is changing the way we approach and interpret medicine and human biology. In the first case, curing the disease only is not sufficient, and care of the patient is of tantamount importance. In the second case, the philosophical debate about the mind-body interaction can find some important answers in the study of placebo effects. Therefore, maybe paradoxically, the placebo effect and the doctor-patient relationship can be approached by using the same biochemical, cellular and physiological tools of the materia medica, which represents an epochal transition from general concepts such as suggestibility and power of mind to a true physiology of the doctor-patient interaction.

Placebo effects in children: a review

Of more than 155,000 PubMed citations found with the search term "placebo," only ~9,000 (5.8%) included the terms "children" or "adolescents." When all these papers were screened, only ~2,000 of them investigated the placebo effect per se, and of those, only ~50 (2.5%) discussed the placebo effect in children and adolescents. In this narrative review, we explore four aspects of the placebo response in children and adolescents: (i) the legal and ethical limitations and restrictions for the inclusion of children in clinical trials as well as in experimental (placebo) research that may explain the poor knowledge base; (ii) the question of whether or not the placebo effect is larger in children and adolescents as compared with adults; (iii) whether the mechanisms underlying the placebo effect are similar between children and adults; and (iv) whether mediators and moderators of the placebo effect are comparable between children and adults. We finally discuss some of the consequences from the current placebo research in adults that may affect both experimental and clinical research in children and adolescents.

Analysis of 34 candidate genes in bupropion and placebo remission

There is considerable variability in the rate of response and remission following treatment with antidepressant drugs or placebo in depression patients. No pharmacogenetic studies of bupropion response have been done. We investigated 532 tagging single nucleotide polymorphisms (SNPs) in 34 candidate genes for association with remission and response to either bupropion (n=319) or placebo (n=257) in patients with major depressive disorder. Analyses were performed using conditional logistic regression. Significant association (gene-wide correction) was observed for remission following treatment with bupropion for a SNP within the serotonin receptor 2A gene (HTR2A rs2770296, p(corrected)=0.02). Response to bupropion treatment was significantly associated with a SNP in the dopamine transporter gene (rs6347, p(corrected)=0.013). Among the patients who received placebo, marginal association for remission was observed between a SNP in HTR2A (rs2296972, p(corrected)=0.055) as well as in the serotonin transporter gene (5-HTT or SLC6A4 rs4251417, p(corrected)=0.050). Placebo response was associated with SNPs in the glucocorticoid receptor gene (NR3C1; rs1048261, p(corrected)=0.040) and monoamine oxidase A gene (MAOA; rs6609257, p corrected=0.046). Although the above observations were significant after gene-wide corrections, none of these would be significant after a more conservative study-wide correction for multiple tests. These results suggest a possible role for HTR2A in remission to bupropion treatment. In accordance with bupropion pharmacology, dopamine transporter may play a role in response. The MAOA gene may be involved in placebo response.

The effect of the serotonin transporter polymorphism (5-HTTLPR) on amygdala function: a meta-analysis

The 5-HTTLPR polymorphism has been widely regarded as a potential genetic risk factor for affective disorders. Consistent with this, this polymorphism has been associated with altered amygdala responses at rest and in response to aversive stimuli. However, the strength of this association remains uncertain. We sought to synthesize existing data on the association between the 5-HTTLPR polymorphism and amygdala activation and ascertain the strength of evidence for this association. Meta-analytic techniques were applied to data from relevant published studies and unpublished data sets to obtain an estimate of the likely magnitude of effect of any association. The large number of studies allowed us to apply a formal test of publication bias, as well as explore the impact of various study-level characteristics on the magnitude of the observed effect size. Our meta-analysis indicated that there is a statistically significant but small effect of 5-HTTLPR on left and right amygdala activity. However, there was considerable between-study heterogeneity, which could not be fully accounted for by the study design and sample characteristics that we investigated. In addition, there was evidence of excess statistical significance among published studies. These findings indicate that the association between the 5-HTTLPR and amygdala activation is smaller than originally thought, and that the majority of previous studies have been considerably under powered to reliably demonstrate an effect of this size.

A neurogenetics approach to understanding individual differences in brain, behavior, and risk for psychopathology

Neurogenetics research has begun to advance our understanding of how genetic variation gives rise to individual differences in brain function, which, in turn, shapes behavior and risk for psychopathology. Despite these advancements, neurogenetics research is currently confronted by three major challenges: (1) conducting research on individual variables with small effects, (2) absence of detailed mechanisms, and (3) a need to translate findings toward greater clinical relevance. In this review, we showcase techniques and developments that address these challenges and highlight the benefits of a neurogenetics approach to understanding brain, behavior and psychopathology. To address the challenge of small effects, we explore approaches including incorporating the environment, modeling epistatic relationships and using multilocus profiles. To address the challenge of mechanism, we explore how non-human animal research, epigenetics research and genome-wide association studies can inform our mechanistic understanding of behaviorally relevant brain function. Finally, to address the challenge of clinical relevance, we examine how neurogenetics research can identify novel therapeutic targets and for whom treatments work best. By addressing these challenges, neurogenetics research is poised to exponentially increase our understanding of how genetic variation interacts with the environment to shape the brain, behavior and risk for psychopathology.

Issues and controversies surrounding the diagnosis and treatment of social anxiety disorder

Although much has been learned about social anxiety disorder (SAD) in recent decades, many questions and controversies surrounding its diagnosis and treatment have remained. Similar to the state of affairs with other psychiatric disorders, no clear pathophysiology has been identified for SAD, and the question of where to draw the line between shyness, SAD and even avoidant personality disorder continues to be debated. Much of the evidence to date suggests that among persons with SAD, it is under-recognized and undertreated; however, other researchers contend that it may be overdiagnosed in some individuals. Questions also remain as to how best treat these individuals, such as with pharmacotherapy, psychotherapy or a combination of the two. The aim of this review is to provide an overview of the controversies related to the diagnosis and treatment of SAD. In addition, suggestions for future research are provided that could perhaps clarify these remaining questions, such as maximizing treatment efficacy by targeting broader outcomes such as quality of life and addressing common comorbidities that occur with SAD.

Corticolimbic brain reactivity to social signals of threat before and after sertraline treatment in generalized social phobia

BACKGROUND

Generalized social phobia (gSP), also known as generalized social anxiety disorder, is characterized by excessive fear of scrutiny by others and pervasive avoidance of social interactions. Pathophysiologic models of gSP implicate exaggerated reactivity of the amygdala and insula in response to social evaluative threat, making them plausible targets for treatment. Although selective serotonin reuptake inhibitor (SSRI) treatment is known to be an effective treatment, little is known about the mechanism through which these agents exert their anxiolytic effects at a brain level in gSP.

METHODS

We acquired functional magnetic resonance imaging data of brain response to social signals of threat (fearful/angry faces) in 21 gSP patients before and after they completed 12 weeks of open-label treatment with the SSRI sertraline. For comparison, 19 healthy control (HC) subjects also underwent two functional magnetic resonance imaging scans, 12 weeks apart.

RESULTS

Whole-brain voxelwise analysis of variance revealed significant Group×Time interactions in the amygdala and the ventral medial prefrontal cortex. Follow-up analyses showed that treatment in gSP subjects reduced amygdala reactivity to fearful faces (which was exaggerated relative to HCs before treatment) and enhanced ventral medial prefrontal cortex activation to angry faces (which was attenuated relative to HCs before treatment). However, these brain changes were not significantly related to social anxiety symptom improvement.

CONCLUSIONS

SSRI treatment response in gSP is associated with changes in a discrete limbic-paralimbic brain network, representing a neural mechanism through which SSRIs may exert their actions.

Therapygenetics: Using genetic markers to predict response to psychological treatment for mood and anxiety disorders

Considerable variation is evident in response to psychological therapies for mood and anxiety disorders. Genetic factors alongside environmental variables and gene-environment interactions are implicated in the etiology of these disorders and it is plausible that these same factors may also be important in predicting individual differences in response to psychological treatment. In this article, we review the evidence that genetic variation influences psychological treatment outcomes with a primary focus on mood and anxiety disorders. Unlike most past work, which has considered prediction of response to pharmacotherapy, this article reviews recent work in the field of therapygenetics, namely the role of genes in predicting psychological treatment response. As this is a field in its infancy, methodological recommendations are made and opportunities for future research are identified.

Recent advances in the brain imaging of social anxiety disorder

Social anxiety disorder (SAD) is one of the most common and disabling anxiety disorders, yet much remains to be learned about its psychobiology. Although functional imaging has emphasized the role of the amygdala and other limbic structures in the neurobiology of SAD, structural and connectivity imaging techniques have emphasized the possibility of abnormalities in other regions and in whole-brain networks. The involvement of a broad range of networks in SAD is consistent with current understandings of the neuroanatomy of emotion and of social processing.

Catechol-O-methyltransferase val158met polymorphism predicts placebo effect in irritable bowel syndrome

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.

Amygdala subregions tied to SSRI and placebo response in patients with social anxiety disorder

The amygdala is a key structure in the pathophysiology of anxiety disorders, and a putative target for anxiolytic treatments. Selective serotonin reuptake inhibitors (SSRIs) and placebo seem to induce anxiolytic effects by attenuating amygdala responsiveness. However, conflicting amygdala findings have also been reported. Moreover, the neural profile of responders and nonresponders is insufficiently characterized and it remains unknown whether SSRIs and placebo engage common or distinct amygdala subregions or different modulatory cortical areas. We examined similarities and differences in the neural response to SSRIs and placebo in patients with social anxiety disorder (SAD). Positron emission tomography (PET) with oxygen-15-labeled water was used to assess regional cerebral blood flow (rCBF) in 72 patients with SAD during an anxiogenic public speaking task, before and after 6-8 weeks of treatment under double-blind conditions. Response rate was determined by the Clinical Global Impression-Improvement scale. Conjunction analysis revealed a common rCBF-attenuation from pre- to post-treatment in responders to SSRIs and placebo in the left basomedial/basolateral and right ventrolateral amygdala. This rCBF pattern correlated with behavioral measures of reduced anxiety and differentiated responders from nonresponders. However, nonanxiolytic treatment effects were also observed in the amygdala. All subgroups, including nonresponders, showed deactivation of the left lateral part of the amygdala. No rCBF differences were found between SSRI responders and placebo responders. This study provides new insights into the brain dynamics underlying anxiety relief by demonstrating common amygdala targets for pharmacologically and psychologically induced anxiety reduction, and by showing that the amygdala is functionally heterogeneous in anxiolysis.

Nocebo phenomena in medicine: their relevance in everyday clinical practice

BACKGROUND

Nocebo phenomena are common in clinical practice and have recently become a popular topic of research and discussion among basic scientists, clinicians, and ethicists.

METHODS

We selectively searched the PubMed database for articles published up to December 2011 that contained the key words "nocebo" or "nocebo effect."

RESULTS

By definition, a nocebo effect is the induction of a symptom perceived as negative by sham treatment and/or by the suggestion of negative expectations. A nocebo response is a negative symptom induced by the patient's own negative expectations and/or by negative suggestions from clinical staff in the absence of any treatment. The underlying mechanisms include learning by Pavlovian conditioning and reaction to expectations induced by verbal information or suggestion. Nocebo responses may come about through unintentional negative suggestion on the part of physicians and nurses. Information about possible complications and negative expectations on the patient's part increases the likelihood of adverse effects. Adverse events under treatment with medications sometimes come about by a nocebo effect.

CONCLUSION

Physicians face an ethical dilemma, as they are required not just to inform patients of the potential complications of treatment, but also to minimize the likelihood of these complications, i.e., to avoid inducing them through the potential nocebo effect of thorough patient information. Possible ways out of the dilemma include emphasizing the fact that the proposed treatment is usually well tolerated, or else getting the patient's permission to inform less than fully about its possible side effects. Communication training in medical school, residency training, and continuing medical education would be desirable so that physicians can better exploit the power of words to patients' benefit, rather than their detriment.

Placebo analgesia: cognitive influences on therapeutic outcome

The therapeutic response to a drug treatment is a mixture of direct pharmacological action and placebo effect. Therefore, harnessing the positive aspects of the placebo effect and reducing the negative ones could potentially benefit the patient. This article is aimed at providing an overview for clinicians of the importance of contextual psychosocial variables in determining treatment response, and the specific focus is on determinants of the placebo response. A better understanding of the physiological, psychological, and social mechanisms of placebo may aid in predicting which contexts have the greatest potential for inducing positive treatment responses. We examine the evidence for the role of psychological traits, including optimism, pessimism, and the effect of patient expectations on therapeutic outcome. We discuss the importance of the patient-practitioner relationship and how this can be used to enhance the placebo effect, and we consider the ethical challenges of using placebos in clinical practice.

Advances in tryptophan hydroxylase-2 gene expression regulation: new insights into serotonin-stress interaction and clinical implications

Serotonin (5-HT) modulates the stress response by interacting with the hormonal hypothalamic-pituitary-adrenal (HPA) axis and neuronal sympathetic nervous system (SNS). Tryptophan hydroxylase (TPH) is the rate-limiting enzyme in 5-HT biosynthesis, and the recent identification of a second, neuron-specific TPH isoform (TPH2) opened up a new area of research. While TPH2 genetic variance has been linked to numerous behavioral traits and disorders, findings on TPH2 gene expression have not only reinforced, but also provided new insights into, the long-recognized but not yet fully understood 5-HT-stress interaction. In this review, we summarize advances in TPH2 expression regulation and its relevance to the stress response and clinical implications. Particularly, based on findings on rhesus monkey TPH2 genetics and other relevant literature, we propose that: (i) upon activation of adrenal cortisol secretion, the cortisol surge induces TPH2 expression and de novo 5-HT synthesis; (ii) the induced 5-HT in turn inhibits cortisol secretion by modulating the adrenal sensitivity to ACTH via the suprachiasmatic nuclei (SCN)-SNS-adrenal system, such that it contributes to the feedback inhibition of cortisol production; (iii) basal TPH2 expression or 5-HT synthesis, as well as early-life experience, influence basal cortisol primarily via the hormonal HPA axis; and (iv) 5'- and 3'-regulatory polymorphisms of TPH2 may differentially influence the stress response, presumably due to their differential roles in gene expression regulation. Our increasing knowledge of TPH2 expression regulation not only helps us better understand the 5-HT-stress interaction and the pathophysiology of neuropsychiatric disorders, but also provides new strategies for the treatment of stress-associated diseases.

A gene-brain-cognition pathway: prefrontal activity mediates the effect of COMT on cognitive control and IQ

A core thesis of cognitive neurogenetic research is that genetic effects on cognitive ability are mediated by specific neural functions, however, demonstrating neural mediation has proved elusive. Pairwise relationships between genetic variation and brain function have yielded heterogeneous findings to date. This heterogeneity indicates that a multiple mediator modeling approach may be useful to account for complex relationships involving function at multiple brain regions. This is relevant not only for characterizing healthy cognition but for modeling the complex neural pathways by which disease-related genetic effects are transmitted to disordered cognitive phenotypes in psychiatric illness. Here, in 160 genotyped functional magnetic resonance imaging participants, we used a multiple mediator model to test a gene-brain-cognition pathway by which activity in 4 prefrontal brain regions mediates the effects of catechol-O-methyltransferase (COMT) gene on cognitive control and IQ. Results provide evidence for gene-brain-cognition mediation and help delineate a pathway by which gene expression contributes to intelligence.