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

Role of expectations in clinical outcomes after deep brain stimulation in patients with Parkinson's disease: a systematic review

Deep brain stimulation (DBS) is a well-established treatment that significantly improves the motor symptoms of patients with Parkinson's disease (PD); however, patients may experience post-operative psychological distress and social maladjustments. This phenomenon has been shown to be related to patients' pre-operative cognitive representations, such as expectations. In this systematic review, we discuss the findings on the role of the expectations of patients with PD regarding the clinical outcomes of DBS to identify areas of intervention to improve pre-operative patient education and promote successful post-operative psychosocial adjustment. PubMed was searched for relevant articles published up to 16 January 2023. Of the 84 identified records, 10 articles focusing on the treatment expectations of patients with PD undergoing DBS were included in this review. The selected studies were conducted among cohorts of patients with different DBS targets, among which the most common was the bilateral subthalamic nucleus. Overall, the data showed that patients' expectations contribute to treatment efficacy. Experiments investigating the placebo effect itself have shown clinical improvement after the induction of positive therapeutic expectations; conversely, unrealistic treatment expectations can affect patient satisfaction after surgery, clinical outcomes, and subjective well-being. This review highlights the need for routine clinical practice to better investigate and manage patients' pre-operative expectations, as well as multidisciplinary education to improve patient satisfaction and psychosocial adjustment after DBS.

Do Polymorphisms Predict Hypnotherapy Response in Children With Functional Abdominal Pain Disorders: An Explorative Study

Genetic variations, in specific COMT , OPRM1 , and MAO-A polymorphisms, have been associated with hypnotizability in adults. The aim of this exploratory study was to investigate whether these polymorphisms are also associated with response to hypnotherapy (HT) in children. Patients (8-18 years, n = 260) diagnosed with a functional abdominal pain disorder (FAPD) from a previous trial assessing HT efficacy were approached for participation and 144 agreed to collect a buccal sample. Primary aim was to explore the association between COMT , OPRM1 , and MAO-A polymorphisms with treatment success (TS) after 3-month HT. Additionally, associations between these polymorphisms and adequate relief, anxiety, depression, quality of life, somatization, hypnotic susceptibility, expectations, pain beliefs, and coping strategies were evaluated. Participants with different variations of COMT , MAO-A , and OPRM1 achieved similar TS levels ( P > 0.05). No associations were found between these polymorphisms and secondary outcomes. This suggest that in pediatric patients with FAPDs, COMT , OPRM1 , and MAO-A polymorphisms do not predict HT response.

Association between personality traits and placebo effects: a preregistered systematic review and meta-analysis

ABSTRACT

Placebo effects are ubiquitous yet highly variable between individuals and therefore strongly affect clinical trial outcomes such as pain relief. It is unclear whether dispositional psychological traits influence responsiveness to placebo. This preregistered meta-analysis and systematic review synthesized the literature investigating the association between personality traits and placebo effects. Based on 21 studies with 798 participants, we performed formal meta-analyses for 10 different personality traits, including behavioral inhibition, fun seeking, goal-drive persistence, reward responsiveness, empathic concern, empathic fantasy, perspective-taking, personal distress, optimism, and anxiety. We did not find evidence of associations between any of these traits and magnitude of placebo effects, which was supported by equivalence tests. Furthermore, we did not find evidence for moderating factors such as placebo manipulation type (conditioning or nonconditioning) or condition (pain or nonpain). These findings challenge the notion that personality influences responsiveness to placebos and contradict its utility for identifying placebo "responders" and "nonresponders."

Functional neurological disorder and placebo and nocebo effects: shared mechanisms

Functional neurological disorder (FND) is characterized by neurological symptoms that cannot be explained by a structural neurological cause. Among the different aetiological models that have been proposed for FND, of note is the Bayesian predictive coding model, which posits that perception relies on top-down cortical predictions (priors) to infer the source of incoming sensory information. This model can also apply to non-pathological experiences, such as placebo and nocebo effects, wherein sensory information is shaped by prior expectations and learning. To date, most studies of the relationship between placebo and nocebo effects and FND have focused on the use of placebos for diagnosis and treatment of FND. Here, we propose that this relationship might go beyond diagnosis and therapy. We develop a framework in which shared cognitive, personality and neuroanatomical factors justify the consideration of a deeper link between FND and placebo and nocebo effects. This new perspective might offer guidance for clarification of the pathogenesis of FND and for the identification of potential biomarkers and therapeutic targets.

Placebo: a brief updated review

Our aims were to provide updated information on placebo/nocebo effect and the potential use of placebo in clinical practice. This article can only provide a rough overview on the placebo and nocebo effect and is intended to serve as a starting point for the reader to go deeper into the corresponding literature. The placebo effect has been observed in multiple medical conditions, after oral administration, with manual therapies as well as with surgery and invasive procedures. The use of placebo in clinical trials is fundamental, although the ethics of its use is under discussion. The placebo may behave like a drug from the pharmacokinetic and pharmacodynamic point of view and can also be associated with adverse events (nocebo effect). Placebo can modify treatment by increasing or decreasing the effects of drugs. The factors associated with the occurrence of placebo effect are multiple, but in addition to those that depend on the placebo itself, the doctor-patient relationship would be the most important. As a result of findings that were published in the last two decades, the psycho-neurobiological basis of placebo is becoming better understood, although further studies are needed. In conclusion, the placebo effect in the clinic exhibits weak to moderate intensity. Placebo, in addition to its use in the clinical trial, should be considered another therapeutic remedy either as stand alone or in association with treatment, and could be useful in certain circumstances. The use of placebo should be regulated by the European health authorities through a guide in clinical practice that will improve patient care.

Genetics of social anxiety disorder: a systematic review

Social anxiety disorder (SAD) is a common psychiatric disorder, often associated with avoidant temperament. Research studies have implicated a strong genetic architecture of SAD. We have conducted a systematic review on the genetics of SAD and yielded 66 articles. In general, prior research studies have focused on the serotonin transporter, oxytocin receptor, brain-derived neurotrophic factor and catechol-O-methyltransferase genes. Mixed and inconsistent results have been reported. Additional approaches and phenotypes have also been investigated, including pharmacogenetics of treatment response, imaging genetics and gene-environment interactions. Future directions warrant further international collaborative efforts, deep-phenotyping of clinical characteristics including consistent and reliable measurement-based symptom severity, and larger sample sizes to ensure sufficient power for stratification due to the heterogeneity of this chronic and often debilitating condition.

Functional Neuroimaging Correlates of Placebo Response in Patients With Depressive or Anxiety Disorders: A Systematic Review

BACKGROUND

The mechanisms underlying placebo effects of psychotropic drugs remain poorly understood. We carried out the first, to our knowledge, systematic review of functional neuroimaging correlates of placebo response in adults with anxiety/depressive disorders.

METHODS

We systematically searched a large set of databases up to February 2021 based on a pre-registered protocol (PROSPERO CRD42019156911). We extracted neuroimaging data related to clinical improvement following placebo or related to placebo mechanisms. We did not perform a meta-analysis due to the small number of included studies and significant heterogeneity in study design and outcome measures.

RESULTS

We found 12 relevant studies for depressive disorders and 4 for anxiety disorders. Activity in the ventral striatum, rostral anterior cingulate cortex and other default mode network regions, orbitofrontal cortex, and dorsolateral prefrontal cortex correlated with placebo antidepressant responses. Activity in regions of the default mode network, including posterior cingulate cortex, was associated with placebo anxiolysis. There was also evidence for possible involvement of the endogenous opioid, dopamine, and serotonin systems in placebo antidepressant and anxiolytic effects.

CONCLUSIONS

Several brain regions and molecular systems may be involved in these placebo effects. Further adequately powered studies exploring causality and controlling for confounders are required.

What is the role of placebo in neurotherapeutics?

INTRODUCTION

The widespread use of the word 'placebo' in the medical literature emphasizes the importance of this phenomenon in modern biomedical sciences. Neuroscientific research over the past thirty years shows that placebo effects are genuine psychobiological events attributable to the overall therapeutic context, and can be robust in both laboratory and clinical settings.

AREAS COVERED

Here the authors describe the biological mechanisms and the clinical implications of placebo effects with particular emphasis on neurology and psychiatry, for example in pain, movement disorders, depression. In these conditions, a number of endogenous systems have been identified, such as endogenous opioids, endocannabinoids, and dopamine, which contribute to the placebo-induced benefit.

EXPERT OPINION

Every effort should be made to maximize the placebo effect and reduce its evil twin, the nocebo effect, in medical practice. This does not require the administration of a placebo, but rather the enhancement of the effects of pharmacological and nonpharmacological treatments through a good doctor-patient interaction.

Chronic intranasal oxytocin reverses stress-induced social avoidance in female prairie voles

Social anxiety disorder (SAD) is a prevalent mental illness in both men and women, but current treatment approaches with selective serotonin reuptake inhibitors (SSRI) have limited success. The neuropeptide oxytocin (OXT) has become a therapeutic target due to its prosocial and anxiolytic effects. Nevertheless, no research has focused on the impact of chronic OXT treatment in animal models of SAD. Social defeat stress is an animal model of social conflict that reliably induces a social avoidance phenotype, reflecting symptoms observed in individuals suffering from SAD. Here, we used the socially monogamous prairie vole, which exhibits aggressive behavior in both sexes, to examine the effects of OXT and SSRI treatment following social defeat stress in males and females. Defeated voles became avoidant in unfamiliar social situations as early as one day after defeat experience, and this phenotype persisted for at least eight weeks. OXT receptor (OXTR) binding in mesocorticolimbic and paralimbic regions was reduced in defeated females during the eight-week recovery period. In males, serotonin 1A receptor binding was decreased in the basolateral amygdala and dorsal raphe nucleus starting at one week and four weeks post-defeat, respectively. Chronic intranasal treatment with OXT had a negative effect on sociability and mesolimbic OXTR binding in non-defeated females. However, chronic intranasal OXT promoted social engagement and increased mesolimbic OXTR binding in defeated females but not males. SSRI treatment led to only modest effects. This study identifies a sex-specific and stress-dependent function of intranasal OXT on mesolimbic OXTR and social behaviors.

Thirty Years of Neuroscientific Investigation of Placebo and Nocebo: The Interesting, the Good, and the Bad

Over the past 30 years there has been a surge of research on the placebo effect using a neuroscientific approach. The interesting aspects of this effort are related to the identification of several biological mechanisms of both the placebo and nocebo effects, the latter of which is defined as a negative placebo effect. Some important translational implications have emerged both in the setting of clinical trials and in routine medical practice. One of the principal contributions of neuroscience has been to draw the attention of the scientific and medical communities to the important role of psychobiological factors in therapeutic outcomes, be they drug related or not. Indeed, many biological mechanisms triggered by placebos and nocebos resemble those modulated by drugs, suggesting a possible interaction between psychological factors and drug action. Unfortunately, this new knowledge regarding placebos has the potential of being dangerously exploited by pseudoscience. Expected final online publication date for the Annual Review of Pharmacology and Toxicology, Volume 62 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Alpha-Glycerylphosphorylcholine Increases Motivation in Healthy Volunteers: A Single-Blind, Randomized, Placebo-Controlled Human Study

Alpha-glycerylphosphorylcholine (αGPC) is a precursor of acetylcholine and can increase acetylcholine concentration in the brain. In addition, αGPC has a role in cholinergic function as well as monoaminergic transmission, including dopaminergic and serotonergic systems. These monoaminergic systems are related to feelings and emotions, including motivation, reward processing, anxiety, and depression. However, the precise effects of αGPC on human feelings and emotions remain to be elucidated. In this study, we investigated changes in the subjective feelings of healthy volunteers using the KOKORO scale before and after administering αGPC. Thirty-nine volunteers participated in a single-blind, placebo-controlled design. Participants completed a KOKORO scale test to quantify self-reported emotional states, three times each day for two weeks preceding treatment and then for a further two weeks while self-administering treatment. αGPC treatment show a tendency to increase motivation during the intervention period. Furthermore, motivation at night was significantly higher in the αGPC group than in the placebo group (p < 0.05). However, αGPC did not show any effects on anxiety. These data suggest that αGPC can be used to increase motivation in healthy individuals.

Effects of Open-Label Placebos on State Anxiety and Glucocorticoid Stress Responses

Stress belongs to the most frequent negative feelings people are confronted with in daily life. Strategies against acute stress include, e.g., relaxation techniques or medications, but it is also known that placebos can successfully reduce negative emotional stress. While it is widely held that placebos require deception to provoke a response, recent studies demonstrate intriguing evidence that placebos may work even without concealment (e.g., against anxiety or pain). Most of these studies are based on self-report questionnaires and do not include physiological measures. Here we report results of a study examining whether placebos without deception reduce acute stress. A total of 53 healthy individuals received either placebos without deception or no pills before participating in a laboratory stress test (Maastricht Acute Stress Test, MAST). We recorded self-report stress measures and cortisol responses before and after the MAST. Results showed no significant differences between the placebo and the control group, but when comparing participants with high relative to low beliefs in the power of placebos we found significant lower anxiety and cortisol responses for the placebo believers. These results show that non-deceptive placebos may successfully reduce acute anxiety and stress, but only in participants who had a strong belief in placebos. We discuss the results by suggesting that open-label placebos might be a possible treatment to reduce stress at least for some individuals.

Influences of hypnotic suggestibility, contextual factors, and EEG alpha on placebo analgesia

We tested the role of hypnotic suggestibility, involuntariness, pain expectation, and subjective hypnotic depth in the prediction of placebo analgesia (PA) responsiveness. We also tested the link of lower and upper alpha sub-band (i.e., 'alpha1' and 'alpha2') power changes with tonic PA responding during waking and hypnosis conditions. Following an initial PA manipulation condition, we recorded EEG activity during waking and hypnosis under two treatments: (1) painful stimulation (Pain); (2) painful stimulation after application of a PA cream. Alpha1 and alpha2 power were derived using the individual alpha frequency method. We found that (1) PA in both waking and hypnosis conditions significantly reduced relative pain perception; (2) during waking, all the above mentioned contextual measures were associated with pain reduction, while involuntariness alone was associated with pain reduction within hypnosis. Enhanced alpha2 power at the left-parietal lead was solely associated with pain reduction in waking, but not in hypnosis condition. Using multiple regression and mediation analyses we found that: (i) during waking, the enhancement of relative left-parietal alpha2 power, directly influenced the enhancement in pain reduction, and, indirectly, through the mediating positive effect of involuntariness; (j) during hypnosis, the enhancement of left-temporoparietal alpha2 power, through the mediation of involuntariness, influenced pain reduction. Current findings obtained during waking suggest that enhanced alpha2 power may serve as a direct-objective measure of the subjective reduction of tonic pain in response to PA treatment. Overall, our findings suggest that placebo analgesia during waking and hypnosis involves different processes of top-down regulation.

The placebo phenomenon and the underlying mechanisms

The clinical role of the placebo effect is a topic of increasing interest for the scientific community. Focus is shifting from the inert role of placebos in randomized controlled trials (RCTs) to potential effects in clinical applications, since the phenomenon is thought to be inherent in routine clinical practice, affecting therapy success rates. Mediation of the mind-brain-body relationship involves both psychosocial and neurobiological factors, the interaction of which comprises the placebo mechanisms. Psychosocial factors include environmentally induced expectations, reward expectations, and even conditioned responses to certain stimuli. Expectations also depend on previous experience of the patient with a similar procedure and can affect future responses. Moreover, the supportive bedside behavior of the clinician and the positive framing of information provided to the patient have proven to be of great importance, setting the foundations for reconsideration of standardized practices. Neurobiological mechanisms mediate these effects through neurotransmitter and neuromodulator pathways. The best understood mechanisms are those regulating non-opioid- and opioid-mediated analgesic responses that implicate specific brain regions of pain control and activation of endogenous opioids. Other responses concern, among others, hormonal control, motor performance, and antidepressant responses. Although mechanisms underlying placebo responses are not as yet completely elucidated, there is substantial evidence suggesting that placebo effects are indicative of healthy functioning of intact brain structures and occur through actual functional changes, and are not simply subjective symptom reports. These effects can be utilized in treatment optimization while maintaining an ethical and respectful manner toward the patient and the standardized disclosure procedures.

A double-blind, placebo-controlled trial on the antihypertensive treatment effect of a quadruple single-pill combination

In a randomized, double‐blind, placebo‐controlled trial, we investigated antihypertensive treatment effect of a quadruple single‐pill combination of reserpine 0.1 mg, dihydralazine 12.5 mg, hydrochlorothiazide 12.5 mg, and triamterene 12.5 mg, and changes in plasma levels of monoamine neurotransmitters (serotonin, norepinephrine, and dopamine) in patients with grade 1 hypertension. Eligible patients with a systolic/diastolic blood pressure (BP, average of six readings at two clinic visits during a 4‐week run‐in period) of 140‐159/90–99 mmHg were randomly assigned to the quadruple combination (n = 30) or placebo (n = 30). The randomized patients were instructed to take a pill of the combination or placebo once daily and followed up at 4, 8, and 12 weeks, respectively. Monoamine neurotransmitters were measured at baseline and 12 weeks of follow‐up. After 12‐week treatment, systolic/diastolic BP significantly (p ≤ .0001) decreased from 140.8 ± 7.9/89.5 ± 7.5 mmHg at baseline by 9.8 ± 1.8/6.4 ± 1.3 mmHg in the combination group. The corresponding values in the placebo group were 141.3 ± 7.9/90.3 ± 7.3 mmHg and 5.2 ± 1.8/0.4 ± 1.3 mmHg, respectively. The between‐group differences in systolic/diastolic BP changes were −4.6/−6.0 mmHg (95% CI, −9.7 to 0.6/−9.7 to −2.2 mmHg, p ≤ .08). The control rate of hypertension was higher in the combination than placebo group (63.3% vs. 16.7%, p = .0002). Plasma serotonin, but not norepinephrine or dopamine, changed in both treatment and placebo groups (p ≤ .01). Nonetheless, plasma norepinephrine tended to decrease in the treatment group (−34.4 pg/ml, p = .09). Adverse events occurred in 5 (16.7%) and 3 (10.0%) patients in the combination and placebo groups, respectively. Our study showed that the quadruple combination reduced BP and caused some changes in plasma neurotransmitters.

Controlling for Placebo Effects in Computerized Cognitive Training Studies With Healthy Older Adults From 2016-2018: Systematic Review

Background

Computerized cognitive training has been proposed as a potential solution to age-related cognitive decline. However, published findings from evaluation studies of cognitive training games, including metastudies and systematic reviews, provide evidence both for and against transferability from trained tasks to untrained cognitive ability. There continues to be no consensus on this issue from the scientific community. Some researchers have proposed that the number of results supporting the efficacy of cognitive training may be inflated due to placebo effects. It has been suggested that placebo effects need to be better controlled by using an active control and measuring participant expectations for improvement in outcome measures.

Objective

This review examined placebo control methodology for recent evaluation studies of computerized cognitive training programs with older adult subjects, specifically looking for the use of an active control and measurement of expectations.

Methods

Data were extracted from PubMed. Evaluation studies of computerized cognitive training with older adult subjects (age ≥50 years) published between 2016 and 2018 were included. Methods sections of studies were searched for (1) control type (active or passive) and subtype (active: active-ingredient or similar-form; passive: no-contact or passive-task); (2) if expectations were measured, how were they measured, and whether they were used in analysis; and (3) whether researchers acknowledged a lack of active control and lack of expectation measurement as limitations (where appropriate).

Results

Of the 19 eligible studies, 4 (21%) measured expectations, and 9 (47%) included an active control condition, all of which were of the similar-form type. The majority of the studies (10/19, 53%) used only a passive control. Of the 9 studies that found results supporting the efficacy of cognitive training, 5 were for far transfer effects. Regarding the limitations, due to practical considerations, the search was limited to one source (PubMed) and to search results only. The search terms may have been too restrictive. Recruitment methods were not analyzed, although this aspect of research may play a critical role in systematically forming groups with different expectations for improvement. The population was limited to healthy older adults, while evaluation studies include other populations and cognitive training types, which may exhibit better or worse placebo control than the studies examined in this review.

Conclusions

Poor placebo control was present in 47% (9/19) of the reviewed studies; however, the studies still published results supporting the effectiveness of cognitive training programs. Of these positive results, 5 were for far transfer effects, which form the basis for broad claims by cognitive training game makers about the scientific validity of their product. For a minimum level of placebo control, future evaluation studies should use a similar-form active control and administer a questionnaire to participants at the end of the training period about their own perceptions of improvement. Researchers are encouraged to think of more methods for the valid measure of expectations at other time points in the training.

Determinants of placebo effects

Determinants of placebo effects and placebo response can be considered from multiple intrinsic and extrinsic perspectives. Intrinsic factors may influence the patient and the clinician/researcher. Patient expectations and previous experiences are considered two of the major intrinsic determinants of placebo response. Other patient determinants include the neural systems under treatment/study, situational factors and reactions to the environment, and personality traits. Clinician/researcher determinants of placebo response include personality factors such as empathy, perceived expertise, the clinical relationship with the patient, and the clinician's belief in the efficacy of the treatment. Extrinsic determinants include the type of study design, influence of advertising or branding, and forces expressed by the cultural milieu. These determinants do not act in isolation, but rather form a complex interaction that ultimately impacts the promotion or deterrence of the placebo effect in clinical and research settings.

Higher- and lower-order personality traits and cluster subtypes in social anxiety disorder

Social anxiety disorder (SAD) can come in different forms, presenting problems for diagnostic classification. Here, we examined personality traits in a large sample of patients (N = 265) diagnosed with SAD in comparison to healthy controls (N = 164) by use of the Revised NEO Personality Inventory (NEO-PI-R) and Karolinska Scales of Personality (KSP). In addition, we identified subtypes of SAD based on cluster analysis of the NEO-PI-R Big Five personality dimensions. Significant group differences in personality traits between patients and controls were noted on all Big Five dimensions except agreeableness. Group differences were further noted on most lower-order facets of NEO-PI-R, and nearly all KSP variables. A logistic regression analysis showed, however, that only neuroticism and extraversion remained significant independent predictors of patient/control group when controlling for the effects of the other Big Five dimensions. Also, only neuroticism and extraversion yielded large effect sizes when SAD patients were compared to Swedish normative data for the NEO-PI-R. A two-step cluster analysis resulted in three separate clusters labelled Prototypical (33%), Introvert-Conscientious (29%), and Instable-Open (38%) SAD. Individuals in the Prototypical cluster deviated most on the Big Five dimensions and they were at the most severe end in profile analyses of social anxiety, self-rated fear during public speaking, trait anxiety, and anxiety-related KSP variables. While additional studies are needed to determine if personality subtypes in SAD differ in etiological and treatment-related factors, the present results demonstrate considerable personality heterogeneity in socially anxious individuals, further underscoring that SAD is a multidimensional disorder.

Can we harness the placebo effect to improve care in lower urinary tract dysfunction? ICI-RS 2019

The proposal "Can we harness the placebo effect to improve care in lower urinary tract dysfunction?" was discussed at the International Consultation on Incontinence-Research Society (ICI-RS) 2019 meeting. The placebo effect can change the treatment outcome whether the treatment is an active treatment or placebo. The total active treatment outcome is a combination of the placebo and the active treatment effect which is seen in placebo-controlled trials. The placebo effect plays an important role in the treatment of lower urinary tract dysfunction in overactive bladder, bladder pain syndrome, and stress urinary incontinence. In clinical practice, a number of factors can be employed to use the placebo effect to maximize its effect on patients receiving an active treatment, such as having the same environment for review such as the same appointment time, same room, and same clinician. Clinicians should also be aware of the nocebo effect which is increased with an overemphasis on side effects or negative outcomes.

Neuroimaging, genetic, clinical, and demographic predictors of treatment response in patients with social anxiety disorder

BACKGROUND

Correct prediction of treatment response is a central goal of precision psychiatry. Here, we tested the predictive accuracy of a variety of pre-treatment patient characteristics, including clinical, demographic, molecular genetic, and neuroimaging markers, for treatment response in patients with social anxiety disorder (SAD).

METHODS

Forty-seven SAD patients (mean±SD age 33.9 ± 9.4 years, 24 women) were randomized and commenced 9 weeks' Internet-delivered cognitive behavior therapy (CBT) combined either with the selective serotonin reuptake inhibitor (SSRI) escitalopram (20 mg daily [10 mg first week], SSRI+CBT, n = 24) or placebo (placebo+CBT, n = 23). Treatment responders were defined from the Clinical Global Impression-Improvement scale (CGI-I ≤ 2). Before treatment, patients underwent functional magnetic resonance imaging and the Multi-Source Interference Task taxing cognitive interference. Support vector machines (SVMs) were trained to separate responders from nonresponders based on pre-treatment neural reactivity in the dorsal anterior cingulate cortex (dACC), amygdala, and occipital cortex, as well as molecular genetic, demographic, and clinical data. SVM models were tested using leave-one-subject-out cross-validation.

RESULTS

The best model separated treatment responders (n = 24) from nonresponders based on pre-treatment dACC reactivity (83% accuracy, P = 0.001). Responders had greater pre-treatment dACC reactivity than nonresponders especially in the SSRI+CBT group. No other variable was associated with clinical response or added predictive accuracy to the dACC SVM model.

LIMITATIONS

Small sample size, especially for genetic analyses. No replication or validation samples were available.

CONCLUSIONS

The findings demonstrate that treatment outcome predictions based on neural cingulate activity, at the individual level, outperform genetic, demographic, and clinical variables for medication-assisted Internet-delivered CBT, supporting the use of neuroimaging in precision psychiatry.

Placebo effects and the molecular biological components involved

Pharmacologically inactive substances have been used in medicine for more than 700 years and can trigger beneficial responses in the human body, which is referred to as the placebo effects or placebo responses. This effect is robust enough to influence psychosocial and physiological responses to the placebo and to active treatments in many settings, which has led to increased interest from researchers. In this article, we summarise the history of placebo, the characteristics of placebo effects and recent advancements reported from the studies on placebo effects and highlight placebome studies to identify various molecular biological components associated with placebo effects. Although placebos have a long history, the placebome concept is still in its infancy. Although behavioural, neurobiological and genetic studies have identified that molecules in the dopamine, opioid, serotonin and endocannabinoid systems might be targets of the placebo effect, placebome studies with a no-treatment control (NTC) are necessary to identify whole-genome genetic targets. Although bioinformatics analysis has identified the molecular placebome module, placebome studies with NTCs are also required to validate the related findings.

Role of placebo effects in pain and neuropsychiatric disorders

The placebo (and the nocebo) effect is a powerful determinant of health outcomes in clinical disease treatment and management. Efforts to completely eradicate placebo effects have shifted dynamically, as increasingly more researchers are tuned to the potentially beneficial effects of incorporating those uncontrollable placebo effects into clinical therapeutic strategies. In this review, we highlight the major findings from placebo research, elucidating the main neurobiological systems and candidate determinants of the placebo phenomenon, and illustrate a perspective that can effectively frame future research on the topic. Finally, we issue a call for increased research on the efficacy of therapeutic strategies that incorporate placebo "tools," and argue that clinical trials of the placebo response in neuropsychiatric diseases and disorders has important and far-reaching translational and clinical relevance.

The influence of reward sensitivity, heart rate dynamics and EEG-delta activity on placebo analgesia

Personality traits have been shown to interact with environmental cues to modulate biological responses including treatment responses, and potentially having a role in the formation of placebo effects. Here we used the Reinforcement Sensitivity Theory Personality Questionnaire (RST-PQ) to identify personality traits that predict placebo analgesic responding. Cardiac inter-beat (RR) time series and electroencephalographic (EEG) band oscillations were recorded from healthy women in a cold-pain (Pain) and placebo analgesia (PA) condition. The measures of Hypnotizability, and self-reported ratings of Hypnotic Depth, Motivation, Pain Expectation, Involuntariness in PA responding, Pain and Distress intensity were obtained. Separate principal components factor analyses with varimax rotation were performed on summarized heart rate variability (HRV) measures of time, frequency, nonlinear Complexity, and EEG-band activity. Both analyses yielded a similar three-factor solution including Frequency HRV (factor-1), Complexity HRV dynamics (factor-2), and time HRV & EEG-delta activity (factor-3). Reward Interest sub-trait of the Behavioral Approach System (BAS-RI), Pain Expectation, Involuntariness in PA responding, and Hypnotic Depth were positively associated, whereas negative changes in time-HRV & EEG-delta scores were associated with Pain Reduction. Multiple mediation analyses disclosed that BAS-RI, potentially served by the dopaminergic system, through Involuntariness in PA responding can alter placebo responding to laboratory pain. Our results also show that a linear compound of HR slowing and higher EEG delta activity during PA explains a substantial proportion of the variance in placebo analgesic responses. Future studies should examine the potential role that these individual difference measures may play in patient responsiveness to treatments for clinical pain.

Amygdala reactivity and connectivity during social and non-social aversive stimulation in social anxiety disorder

Social anxiety disorder (SAD) is characterized by exaggerated amygdala reactivity in response to symptom provocation, but it is unclear if such hyper-reactivity is elicited by disorder-specific challenges only or characterizes reactions to aversive stimuli in general. Here, using functional magnetic resonance imaging in 14 patients with SAD, as compared to 12 healthy controls, we found that amygdala hyper-reactivity is confined to disorder-relevant social stimulation. SAD patients displayed increased amygdala reactivity to fearful as compared to neutral facial pictures, but not in response to generally aversive but mainly non-social stimulation when compared to neutral pictorial stimuli taken from the International Affective Picture System. The increased amygdala reactivity was not mediated by an altered prefrontal inhibition among SAD patients as compared to controls, suggesting increased bottom-up processes rather than attenuated top-down control. In conclusion, the enhanced amygdala reactivity in SAD seems specific to socially relevant stimuli rather than aversive stimuli in general.

Placebo Effects in Traumatic Brain Injury

In recent years, several randomized controlled trials evaluating pharmaceutical treatments for traumatic brain injury (TBI) have failed to demonstrate efficacy over placebo, with both active and placebo arms improving at comparable rates. These findings could be viewed in opposing ways, suggesting on the one hand failure of the tested outcome, but on the other, representing evidence of robust placebo effects in TBI. In this article, we examine several of the primary psychological processes driving placebo effects (verbal suggestion, cognitive re-framing, interpersonal interactions, conditioning, therapeutic alliance, anxiety reduction) as well as placebo neurobiology (top-down cortical regulation, reward system activation, dopaminergic and serotonergic neurotransmission). We then extrapolate from the literature to explore whether something inherent in TBI makes it particularly responsive to placebos. Viewed as such here, placebos may indeed represent a powerful and effective treatment for a variety of post-TBI complaints.

Previously reported placebo-response-associated variants do not predict patient outcomes in inflammatory disease Phase III trial placebo arms

In clinical trials, a placebo response refers to improvement in disease symptoms arising from the psychological effect of receiving a treatment rather than the actual treatment under investigation. Previous research has reported genomic variation associated with the likelihood of observing a placebo response, but these studies have been limited in scope and have not been validated. Here, we analyzed whole-genome sequencing data from 784 patients undergoing placebo treatment in Phase III Asthma or Rheumatoid Arthritis trials to assess the impact of previously reported variation on patient outcomes in the placebo arms and to identify novel variants associated with the placebo response. Contrary to expectations based on previous reports, we did not observe any statistically significant associations between genomic variants and placebo treatment outcome. Our findings suggest that the biological origin of the placebo response is complex and likely to be variable between disease areas.

Do You Believe It? Verbal Suggestions Influence the Clinical and Neural Effects of Escitalopram in Social Anxiety Disorder: A Randomized Trial

Background

Selective serotonin reuptake inhibitors (SSRIs) are commonly prescribed for depression and anxiety, but their efficacy relative to placebo has been questioned. We aimed to test how manipulation of verbally induced expectancies, central for placebo, influences SSRI treatment outcome and brain activity in patients with social anxiety disorder (SAD).

Methods

We did a randomized clinical trial, within an academic medical center (Uppsala, Sweden), of individuals fulfilling the DSM-IV criteria for SAD, recruited through media advertising. Participants were 18 years or older and randomized in blocks, through a computer-generated sequence by an independent party, to nine weeks of overt or covert treatment with escitalopram (20 mg daily). The overt group received correct treatment information whereas the covert group was treated deceptively with the SSRI described, by the psychiatrist, as active placebo. The treating psychiatrist was necessarily unmasked while the research staff was masked from intervention assignment. Treatment efficacy was assessed primarily with the self-rated Liebowitz Social Anxiety Scale (LSAS-SR), administered at week 0, 1, 3, 6 and 9, also yielding a dichotomous estimate of responder status (clinically significant improvement). Before and at the last week of treatment, brain activity during an emotional face-matching task was assessed with functional magnetic resonance imaging (fMRI) and during fMRI sessions, anticipatory speech anxiety was also assessed with the Spielberger State-Trait Anxiety Inventory - State version (STAI-S). Analyses included all randomized patients with outcome data at posttreatment. This study is registered at ISRCTN, number 98890605.

Findings

Between March 17th 2014 and May 22nd 2015, 47 patients were recruited. One patient in the covert group dropped out after a few days of treatment and did not provide fMRI data, leaving 46 patients with complete outcome data. After nine weeks of treatment, overt (n = 24) as compared to covert (n = 22) SSRI administration yielded significantly better outcome on the LSAS-SR (adjusted difference 21.17, 95% CI 10.69–31.65, p < 0.0001) with more than three times higher response rate (50% vs. 14%; χ²(1) = 6.91, p = 0.009) and twice the effect size (d = 2.24 vs. d = 1.13) from pre-to posttreatment. There was no significant between-group difference on anticipatory speech anxiety (STAI-S), both groups improving with treatment. No serious adverse reactions were recorded. On fMRI outcomes, there was suggestive evidence for a differential neural response to treatment between groups in the posterior cingulate, superior temporal and inferior frontal gyri (all z thresholds exceeding 3.68, p ≤ 0.001). Reduced social anxiety with treatment correlated significantly with enhanced posterior cingulate (z threshold 3.24, p = 0.0006) and attenuated amygdala (z threshold 2.70, p = 0.003) activity.

Interpretation

The clinical and neural effects of escitalopram were markedly influenced by verbal suggestions. This points to a pronounced placebo component in SSRI-treatment of SAD and favors a biopsychosocial over a biomedical explanatory model for SSRI efficacy.

Funding resources

The Swedish Research Council for Working Life and Social Research (grant 2011-1368), the Swedish Research Council (grant 421-2013-1366), Riksbankens Jubileumsfond – the Swedish Foundation for Humanities and Social Sciences (grant P13-1270:1).

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Overt surpassed covert SSRI treatment with doubled effect size and tripled response rate on the main social anxiety outcome.

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Overt vs. covert SSRI treatment yielded different neural changes in brain areas involved in emotion-cognition interactions.

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This study suggests that the presentation of a treatment may be as important as the treatment itself.

Using truthful or deceiving verbal instructions, we tested how expectancies influence SSRI efficacy in social anxiety disorder. The number of responders was more than three times higher after open administration of escitalopram 20 mg compared to covert administration of the drug presented as “active placebo” in a cover story. Correct vs. incorrect information about the SSRI also yielded different neural changes in brain areas involved in emotion-cognition interactions. The benefit of SSRI medication seems to be highly affected by psychological factors like positive expectancies traditionally associated with placebo. Our results favor a biopsychosocial over a biomedical explanatory model for SSRI efficacy.

Genome-wide association studies of placebo and duloxetine response in major depressive disorder

We investigated variants associated with treatment response in depressed patients treated with either the antidepressant duloxetine or placebo using a genome-wide approach. Our sample (N=391) included individuals aged 18-75 years, diagnosed with major depressive disorder and treated with either duloxetine or placebo for up to 8 weeks. We conducted genome-wide associations for treatment response as operationalized by percentage change in Montgomery-Åsberg Depression Rating Scale score from baseline, as well as mixed models analyses across five time points. In the placebo-treated subsample (N=205), we observed a genome-wide association with rs76767803 (β=0.69, P=1.25 × 10^-8) upstream of STAC1. STAC1 rs76767803 was also associated with response using mixed model analysis (χ²=3.95; P=0.001). In the duloxetine-treated subsample (N=186), we observed suggestive associations with ZNF385D (rs4261893; β=-0.46, P=1.55 × 10^-5), NCAM1 (rs2303377; β=0.45, P=1.76 × 10^-5) and MLL5 (rs117986340; β=0.91, P=3.04 × 10^-5). Our findings suggest that a variant upstream of STAC1 is associated with placebo response, which might have implications for treatment optimization, clinical trial design and drug development.

Network analysis of the genomic basis of the placebo effect

The placebo effect is a phenomenon in which patients who are given an inactive treatment (e.g., inert pill) show a perceived or actual improvement in a medical condition. Placebo effects in clinical trials have been investigated for many years especially because placebo treatments often serve as the control arm of randomized clinical trial designs. Recent observations suggest that placebo effects may be modified by genetics. This observation has given rise to the term "placebome," which refers to a group of genome-related mediators that affect an individual's response to placebo treatments. In this study, we conduct a network analysis of the placebome and identify a placebome module in the comprehensive human interactome using a seed-connector algorithm. The placebome module is significantly enriched with neurotransmitter signaling pathways and brain-specific proteins. We validate the placebome module using a large cohort of the Women's Genome Health Study (WGHS) trial and demonstrate that the placebome module is significantly enriched with genes whose SNPs modify the outcome in the placebo arm of the trial. To gain insights into placebo effects in different diseases and drug treatments, we use a network proximity measure to examine the closeness of the placebome module to different disease modules and drug target modules. The results demonstrate that the network proximity of the placebome module to disease modules in the interactome significantly correlates with the strength of the placebo effect in the corresponding diseases. The proximity of the placebome module to molecular pathways affected by certain drug classes indicates the existence of placebo-drug interactions. This study is helpful for understanding the molecular mechanisms mediating the placebo response, and sets the stage for minimizing its effects in clinical trials and for developing therapeutic strategies that intentionally engage it.

Placebo response in pain, fatigue, and performance: Possible implications for neuromuscular disorders

The placebo response in neuromuscular disorders is not well understood. The only available data regarding its underlying mechanisms are related to neuropathic pain. In this review, we describe the factors that contribute to improved outcomes in the placebo arm, with specific attention to pain and fatigue, as well as some of the most important psychobiological mechanisms that may explain such a response. This approach may also improve our insight into the symptomatology and therapeutic responses of other neuromuscular disorders. The fact that >90% of tested analgesics for neuropathic pain have failed in advanced phases of clinical trials should prompt a greater investment of effort and resources into understanding the mechanisms and impact of placebos in clinical research. Such an endeavor will help improve the design of clinical trials and will provide information that informs clinical neuromuscular practice. Muscle Nerve 56: 358-367, 2017.

Within-session effect of repeated stress exposure on extinction circuitry function in social anxiety disorder

Anxiety reduction following repeated exposure to stressful experiences is generally held to depend on neural processes involved in extinction of conditioned fear. We predicted that repeated exposure to stressful experiences would change activity throughout the circuitry serving extinction, including ventromedial prefrontal cortex (vmPFC), the hippocampus and the amygdala. To test this prediction, 36 participants diagnosed with SAD performed two successive speeches in front of an observing audience while regional cerebral blood flow (rCBF) was recorded using positron emission tomography. To control for non-anxiolytic effects of repeated exposure, rCBF was also measured during repeated presentations of neutral and angry facial expressions. Results showed that anxiety ratings and heart rate decreased from the first to the second speech, indicating an anxiolytic effect of repeated exposure. Exposure attenuated rCBF in the amygdala whereas no change in rCBF was observed in the vmPFC or hippocampus. The rCBF-reductions in the amygdala were greater following repetition of the speech task than repetition of face exposure indicating that they were specific to anxiety attenuation and not due to a reduced novelty. Our findings suggest that amygdala-related attenuation processes are key to understanding the working mechanisms of exposure therapy.

Nature of the placebo and nocebo effect in relation to functional neurologic disorders

Placebos have long been considered a nuisance in clinical research, for they have always been used as comparators for the validation of new treatments. By contrast, today they represent an active field of research, and, due to the involvement of many mechanisms, the study of the placebo effect can actually be viewed as a melting pot of concepts and ideas for neuroscience. There is not a single placebo effect, but many, with different mechanisms across different medical conditions and therapeutic interventions. Expectation, anxiety, and reward are all involved, as well as a variety of learning phenomena and genetic variants. The most productive models to better understand the neurobiology of the placebo effect are pain and Parkinson's disease. In these medical conditions, several neurotransmitters have been identified, such as endogenous opioids, cholecystokinin, dopamine, as well as lipidic mediators, for example, endocannabinoids and prostaglandins. Since the placebo effect is basically a psychosocial context effect, these data indicate that different social stimuli, such as words and therapeutic rituals, may change the chemistry of the patient's brain, and these effects are similar to those induced by drugs.

The Placebo and Nocebo Phenomena: Their Clinical Management and Impact on Treatment Outcomes

PURPOSE

This overview focuses on placebo and nocebo effects in clinical trials and routine care. Our goal was to propose strategies to improve outcomes in clinical practice, maximizing placebo effects and reducing nocebo effects, as well as managing these phenomena in clinical trials.

METHODS

A narrative literature search of PubMed was conducted (January 1980-September 2016). Systematic reviews, randomized controlled trials, observational studies, and case series that had an emphasis on placebo or nocebo effects in clinical practice were included in the qualitative synthesis. Search terms included: placebo, nocebo, clinical, clinical trial, clinical setting, placebo effect, nocebo effect, adverse effects, and treatment outcomes. This search was augmented by a manual search of the references of the key articles and the related literature.

FINDINGS

Placebo and nocebo effects are psychobiological events imputable to the therapeutic context. Placebo is defined as an inert substance that provokes perceived benefits, whereas the term nocebo is used when an inert substance causes perceived harm. Their major mechanisms are expectancy and classical conditioning. Placebo is used in several fields of medicine, as a diagnostic tool or to reduce drug dosage. Placebo/nocebo effects are difficult to disentangle from the natural course of illness or the actual effects of a new drug in a clinical trial. There are known strategies to enhance clinical results by manipulating expectations and conditioning.

IMPLICATIONS

Placebo and nocebo effects occur frequently and are clinically significant but are underrecognized in clinical practice. Physicians should be able to recognize these phenomena and master tactics on how to manage these effects to enhance the quality of clinical practice.

Does the model of additive effect in placebo research still hold true? A narrative review

Personalised and contextualised care has been turned into a major demand by people involved in healthcare suggesting to move toward person-centred medicine. The assessment of person-centred medicine can be most effectively achieved if treatments are investigated using ‘with versus without’ person-centredness or integrative study designs. However, this assumes that the components of an integrative or person-centred intervention have an additive relationship to produce the total effect. Beecher’s model of additivity assumes an additive relation between placebo and drug effects and is thus presenting an arithmetic summation. So far, no review has been carried out assessing the validity of the additive model, which is to be questioned and more closely investigated in this review.

Initial searches for primary studies were undertaken in July 2016 using Pubmed and Google Scholar. In order to find matching publications of similar magnitude for the comparison part of this review, corresponding matches for all included reviews were sought.

A total of 22 reviews and 3 clinical and experimental studies fulfilled the inclusion criteria. The results pointed to the following factors actively questioning the additive model: interactions of various effects, trial design, conditioning, context effects and factors, neurobiological factors, mechanism of action, statistical factors, intervention-specific factors (alcohol, caffeine), side-effects and type of intervention.

All but one of the closely assessed publications was questioning the additive model. A closer examination of study design is necessary. An attempt in a more systematic approach geared towards solutions could be a suggestion for future research in this field.

Can Matching-Adjusted Indirect Comparison Methods Mitigate Placebo Response Differences Among Patient Populations in Adjunctive Trials of Brivaracetam and Levetiracetam?

BACKGROUND AND OBJECTIVE

Patients with focal seizures recruited into adjunctive antiepileptic drug (AED) trials have become more refractory and severe over time; concurrently, placebo responses have increased. To attempt to account for heterogeneity among trials, propensity-score weighted patient-level data were used to indirectly compare placebo responses reported in brivaracetam and levetiracetam trials.

METHODS

Patient-level data from randomised, placebo-controlled brivaracetam (recruited 2007-2014) and levetiracetam (1993-1998) trials were pooled. Consistent inclusion/exclusion criteria were applied and outcomes were defined consistently. Potentially confounding baseline characteristics were adjusted for using propensity score weighting. Weighting success was assessed using placebo response.

RESULTS

In total, 707 and 473 active drug and 399 and 253 placebo patients comprised the brivaracetam and levetiracetam groups, respectively. Before weighting, several baseline variables were significantly different between groups; after weighting, prior vagal nerve stimulation, co-morbid depression and co-morbid anxiety remained different. Before weighting, median seizure frequency reduction was 21.7 and 3.9% in the brivaracetam and levetiracetam placebo arms, respectively; after weighting, median reduction was 15.0 and 6.0%. The comparison of non-randomised groups could be biased by unobserved confounding factors and region of residence. Lifetime AED history was unavailable in the brivaracetam trials and excluded from analysis.

CONCLUSIONS

Placebo responses remained different between brivaracetam and levetiracetam trials after propensity score weighting, indicating the presence of residual confounding factors associated with placebo response in these trials. It therefore remains problematic to conduct reliable indirect comparisons of brivaracetam and levetiracetam given the current evidence base, which may apply to comparisons between other AED trials.

Reduced serotonin synthesis and regional cerebral blood flow after anxiolytic treatment of social anxiety disorder

Social anxiety disorder (SAD) is associated with increased fear-related neural activity in the amygdala and we recently found enhanced serotonin synthesis rate in the same region. Anxiolytic agents like selective serotonin re-uptake inhibitors (SSRIs) and neurokinin-1 receptor (NK1R) antagonists reduce amygdala activity and may attenuate serotonin formation according to animal studies. Here, we examined the effects of SSRI pharmacotherapy, NK1R antagonism, and placebo on serotonin synthesis rate in relation to neural activity, measured as regional cerebral blood flow (rCBF), and symptom improvement in SAD. Eighteen SAD patients were randomized to receive daily double-blind treatment for six weeks either with the SSRI citalopram (n=6; 40mg), the NK1R antagonist GR205171 (n=6; 5mg; 4 weeks following 2 weeks of placebo), or placebo (n=6). Serotonin synthesis rate at rest and rCBF during stressful public speaking were assessed, before and after treatment, using positron emission tomography with the tracers [¹¹C]5-hydroxytryptophan and [¹⁵O]water respectively. The Liebowitz Social Anxiety Scale (LSAS-SR) indexed symptom severity. All groups exhibited attenuated amygdala serotonin synthesis rate after treatment, which was associated with reduced amygdala rCBF during public speaking and accompanied by symptom improvement. These results are consistent with the notion that serotonin in the amygdala exerts an anxiogenic influence and, conversely, that anxiolysis is achieved through decreased serotonin formation in the amygdala.

Serotonin synthesis rate and the tryptophan hydroxylase-2: G-703T polymorphism in social anxiety disorder

It is disputed whether anxiety disorders, like social anxiety disorder, are characterized by serotonin over- or underactivity. Here, we evaluated whether our recent finding of elevated neural serotonin synthesis rate in patients with social anxiety disorder could be reproduced in a separate cohort, and whether allelic variation in the tryptophan hydroxylase-2 (TPH2) G-703T polymorphism relates to differences in serotonin synthesis assessed with positron emission tomography. Eighteen social anxiety disorder patients and six healthy controls were scanned during 60 minutes in a resting state using positron emission tomography and 5-hydroxy-L-[β -(11)C]tryptophan, [(11)C]5-HTP, a substrate of the second enzymatic step in serotonin synthesis. Parametric images were generated, using the reference Patlak method, and analysed using Statistical Parametric Mapping (SPM8). Blood samples for genotyping of the TPH2 G-703T polymorphism were obtained from 16 social anxiety disorder patients (T carriers: n=5, GG carriers: n=11). A significantly elevated [(11)C]5-HTP accumulation rate, indicative of enhanced decarboxylase activity and thereby serotonin synthesis capacity, was detected in social anxiety disorder patients compared with controls in the hippocampus and basal ganglia nuclei and, at a more lenient (uncorrected) statistical threshold, in the amygdala and anterior cingulate cortex. In patients, the serotonin synthesis rate in the amygdala and anterior cingulate cortex was significantly elevated in TPH2 T carriers in comparison with GG homozygotes. Our results support that social anxiety disorder entails an overactive presynaptic serotonergic system that, in turn, seems functionally influenced by the TPH2 G-703T polymorphism in emotionally relevant brain regions.

Biological markers for anxiety disorders, OCD and PTSD - a consensus statement. Part I: Neuroimaging and genetics

OBJECTIVES

Biomarkers are defined as anatomical, biochemical or physiological traits that are specific to certain disorders or syndromes. The objective of this paper is to summarise the current knowledge of biomarkers for anxiety disorders, obsessive-compulsive disorder (OCD) and post-traumatic stress disorder (PTSD).

METHODS

Findings in biomarker research were reviewed by a task force of international experts in the field, consisting of members of the World Federation of Societies for Biological Psychiatry Task Force on Biological Markers and of the European College of Neuropsychopharmacology Anxiety Disorders Research Network.

RESULTS

The present article (Part I) summarises findings on potential biomarkers in neuroimaging studies, including structural brain morphology, functional magnetic resonance imaging and techniques for measuring metabolic changes, including positron emission tomography and others. Furthermore, this review reports on the clinical and molecular genetic findings of family, twin, linkage, association and genome-wide association studies. Part II of the review focuses on neurochemistry, neurophysiology and neurocognition.

CONCLUSIONS

Although at present, none of the putative biomarkers is sufficient and specific as a diagnostic tool, an abundance of high-quality research has accumulated that will improve our understanding of the neurobiological causes of anxiety disorders, OCD and PTSD.

Genetic variation in the tryptophan hydroxylase 2 gene moderates depressive symptom trajectories and remission over 8 weeks of escitalopram treatment

The serotonin system plays an important role in the pathogenesis of major depressive disorder (MDD) and genetic variations in serotonin-related genes affect the efficacy of antidepressants. The aim of this study was to investigate the relationship between genotypic variation in six candidate serotonergic genes (ADCY9, HTR1B, GNB3, HTR2A, TPH2, SLC6A4) and depressive and anxiety symptom severity trajectories as well as remission following escitalopram treatment. A total of 166 Chinese patients with MDD were treated with escitalopram (open-label) for 8 weeks. TPH2 rs4570625 GG carriers were more likely to achieve depressive and anxiety symptom remission compared with T-allele carriers. At the trend level (P(corrected)=0.05), depressive symptom severity trajectories were moderated by TPH2 rs4570625. Patients with the GT or the GG genotype showed more favorable depressive symptom severity trajectories compared with TT genotype carriers. Polymorphisms in ADCY9, HTR1B, and HTR2A were nominally associated with symptom remission, but did not withstand correction for multiple comparisons. The HTTLPR polymorphism was not included in our final analysis because of a high percentage of missing data. These results suggested that genotypic variation in TPH2 may moderate the therapeutic response to esciatlopram among Chinese patients with MDD.

Developmental psychopathology in an era of molecular genetics and neuroimaging: A developmental neurogenetics approach

The emerging field of neurogenetics seeks to model the complex pathways from gene to brain to behavior. This field has focused on imaging genetics techniques that examine how variability in common genetic polymorphisms predict differences in brain structure and function. These studies are informed by other complimentary techniques (e.g., animal models and multimodal imaging) and have recently begun to incorporate the environment through examination of Imaging Gene × Environment interactions. Though neurogenetics has the potential to inform our understanding of the development of psychopathology, there has been little integration between principles of neurogenetics and developmental psychopathology. The paper describes a neurogenetics and Imaging Gene × Environment approach and how these approaches have been usefully applied to the study of psychopathology. Six tenets of developmental psychopathology (the structure of phenotypes, the importance of exploring mechanisms, the conditional nature of risk, the complexity of multilevel pathways, the role of development, and the importance of who is studied) are identified, and how these principles can further neurogenetics applications to understanding the development of psychopathology is discussed. A major issue of this piece is how neurogenetics and current imaging and molecular genetics approaches can be incorporated into developmental psychopathology perspectives with a goal of providing models for better understanding pathways from among genes, environments, the brain, and behavior.