Placebo eff ects in psychiatry: mediators and moderators

A narrative review of the placebo effect: historical roots, current applications, and emerging insights

PURPOSE

Placebo is a term to define physiologically inactive compounds used in treatment that causes physical and emotional changes. The placebo effect, driven by expectation and conditioning, plays a significant role in various conditions like pain, depression, and Parkinson's disease, while the nocebo effect can hinder treatment outcomes. Understanding mechanisms such as neuromodulation and genetics has gained importance in modern medicine. This review aims to explore the clinical relevance of placebo responses, particularly in neuropsychiatric disorders, and their potential in personalized medicine. By integrating placebo research into healthcare, it highlights opportunities to enhance treatment efficacy, improve patient well-being, and reduce reliance on pharmacological interventions.

METHODS

A comprehensive literature search was conducted in PubMed, Scopus, and Google Scholar databases. Recent studies were reviewed to evaluate placebo effects, and the variability of the placebo response in neuropsychiatric disorders was summarized.

RESULTS

Placebo effects significantly impact treatment outcomes across various conditions, including Parkinson's disease, depression, pain syndromes, and epilepsy. The mechanisms involve neurobiological and psychological factors, with evidence suggesting that placebo interventions can modulate neurotransmitter activity and improve patient well-being.

CONCLUSION

Integrating placebo research into clinical practice may enhance treatment outcomes, reduce drug dependency, and support personalized medicine by tailoring interventions to individual placebo responsiveness. Understanding placebo and nocebo mechanisms can optimize therapeutic strategies while minimizing unnecessary pharmacological treatments.

Combined pharmacological and psychosocial interventions for alcohol use disorder

BACKGROUND

Alcohol use disorder (AUD) is a mental disorder characterised by a strong desire to consume alcohol and impaired control of alcohol use, with devastating consequences. Many people with AUD do not respond to psychosocial or pharmacological interventions when these are provided alone. Combining these interventions may improve the response to treatment, though evidence remains limited.

OBJECTIVES

To assess the effects of combined pharmacological and psychosocial interventions for the treatment of AUD in adults.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, three other databases, and two trials registers in November 2023, without language restrictions.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing combined pharmacological and psychosocial interventions versus pharmacological or psychosocial interventions alone, or no intervention/treatment as usual (TAU), in adults with AUD. Our primary outcomes were continuous abstinent participants, frequency of use (measured as heavy drinkers, percentages of abstinent days, heavy-drinking days), amount of use (number of drinks per drinking day), adverse events, serious adverse events, dropouts from treatment, and dropouts due to adverse events.

DATA COLLECTION AND ANALYSIS

We assessed risk of bias using Cochrane's RoB 1 tool, performed random-effects meta-analyses, and evaluated the certainty of evidence according to the GRADE approach.

MAIN RESULTS

We included 21 RCTs (4746 participants). The most studied pharmacological and psychosocial interventions were naltrexone (81.0%) and cognitive behavioural therapy (66.7%), respectively. Most participants were men (74%), aged about 44 years, with AUD, without comorbid mental disorders or other substance use disorders; 15 RCTs detoxified participants before treatment. We judged 28.5% of the studies as at low risk of bias for random sequence generation, allocation concealment, performance bias for objective and subjective outcomes, and detection bias for subjective outcomes; all studies were at low risk of detection bias for objective outcomes; 85.7% of studies were at low risk of attrition bias; 14.2% of studies were at low risk of reporting bias. 1) Compared to psychosocial intervention alone, combined pharmacological and psychosocial interventions probably reduce the number of heavy drinkers (above the clinically meaningful threshold (MID) of 2%; absolute difference (AD) -10%, 95% confidence interval (CI) -18% to -2%; risk ratio (RR) 0.86, 95% CI 0.76 to 0.97; 8 studies, 1609 participants; moderate-certainty evidence). They may increase continuous abstinent participants (MID 5%; AD 5%, 95% CI 1% to 11%; RR 1.17, 95% CI 1.02 to 1.34; 6 studies, 1184 participants; low-certainty evidence). They probably have little to no effect on: • the rate of abstinent days (MID 8%; mean difference (MD) 4.16, 95% CI 1.24 to 7.08; 10 studies, 2227 participants); • serious adverse events (MID 1%; AD -2%, 95% CI -3% to 0%; RR 0.20, 95% CI 0.03 to 1.12; 4 studies; 524 participants); • dropouts from treatment (MID 10%; AD -3%, 95% CI -5% to 0%; RR 0.89, 95% CI 0.79 to 1.01; 15 studies, 3021 participants); and • dropouts due to adverse events (MID 5%; AD 2%, 95% CI 0% to 5%; RR 1.91, 95% CI 1.04 to 3.52; 8 studies, 1572 participants) (all moderate-certainty evidence). They may have little to no effect on: • heavy-drinking days (MID 5%; MD -3.49, 95% CI -8.68 to 1.70; 4 studies, 470 participants); • number of drinks per drinking day (MID 1 drink; MD -0.57, 95% CI -1.16 to 0.01; 7 studies, 805 participants); and • adverse events (MID 30%; AD 17%, 95% CI -5% to 46%; RR 1.25, 95% CI 0.93 to 1.68; 4 studies, 508 participants) (all low-certainty evidence). 2) Compared to pharmacological intervention alone, combined pharmacological and psychosocial interventions may have little to no effect on: • the rate of abstinent days (MID 8%; MD -1.18, 95% CI -4.42 to 2.07; 2 studies, 1158 participants); and • dropouts from treatment (MID 10%; AD 1%, 95% CI -10 to 14%; RR 0.98, 95% CI 0.65 to 1.47; 3 studies, 1246 participants) (all low-certainty evidence). We are uncertain about their effect on: • continuous abstinent participants (MID 5%; AD 3%, 95% CI -5% to 18%; RR 1.22, 95% CI 0.62 to 2.40; 1 study, 241 participants); • the number of heavy drinkers (MID 2%; AD 2%, 95% CI -4% to 8%; RR 1.03, 95% CI 0.94 to 1.12; 1 study, 917 participants); • the number of drinks per drinking day (MID 1 drink; MD -2.40, 95% CI -3.98 to -0.82; 1 study, 241 participants); and • dropouts due to adverse events (MID 5%; AD -1%, 95% CI -3% to 6%; RR 0.61, 95% CI 0.14 to 2.72; 2 studies, 1165 participants) (all very low-certainty evidence). 3) We are uncertain about the effect of combined pharmacological and psychosocial interventions, when compared to TAU, on: • the number of heavy drinkers (MID 2%; AD -5%, 95% CI -13% to 2%; RR 0.93, 95% CI 0.83 to 1.03; 1 study, 616 participants); • the rate of abstinent days (MID 8%; MD 3.43, 95% CI -1.32 to 8.18; 1 study, 616 participants); • dropouts from treatment (MID 10%; AD 0%, 95% CI -10% to 15%; RR 0.98, 95% CI 0.58 to 1.65; 2 studies, 696 participants); and • dropouts due to adverse events (MID 5%; AD 3%, 95% CI 0% to 15%; RR 2.97, 95% CI 0.70 to 12.67; 1 study, 616 participants) (all very low-certainty evidence). The certainty of evidence ranged from moderate to very low, downgraded mainly due to risk of bias and imprecision.

AUTHORS' CONCLUSIONS

As implications for practice, our findings indicate that adding pharmacological to psychosocial interventions is safe and helps people with AUD recover. These conclusions are based on low- to moderate-certainty evidence. Given the few studies and very low-certainty evidence, any benefits of adding psychosocial to pharmacological interventions or comparing the combined intervention to TAU are less clear. As implications for research, further studies should investigate the effects of the combined intervention compared to pharmacotherapy or TAU.

The prediction of the analgesic placebo response is moderated by outward-focused attention: A sham, randomized clinical trial of chronic back pain patients

The within-subject variability (WSV) of pain-intensity reports has gained attention as a predictor of the placebo response but has demonstrated mixed results. We hypothesized that participants' inward- and outward-directed attention will moderate WSV's prediction of the analgesic placebo response. In this sham randomized clinical trial (protocol number NCT05994118); placebo response was induced in chronic back-pain patients (n=113) through a saline injection plus verbal suggestion. The WSV assessed by the focused analgesia selection test (FAST) served as a predictor. The revised Self-Consciousness Scale (SCS-R), evaluating a person's tendency to focus attention inward or outward was used to moderate the prediction. The placebo response prediction was significantly moderated by 2 SCS-R subscales: public self-consciousness (b = 46.36, SE = 23.08, t = 2.0, p = 0.047) and social anxiety (b = 44.01, SE = 18.02, t = 2.44, p = 0.016). The prediction was significant at low levels of both moderators (p < 0.01), but not at high levels of these traits. Prediction of the placebo response is of value and could promote personalized medical care. Better understanding of factors shaping the placebo response could further contribute to both clinical practice and clinical trials. PERSPECTIVE: The current study demonstrates that the prediction of the analgesic placebo response could be improved if relevant personal characteristics are included as moderators of the prediction. Better predictions of the placebo response could contribute to improve both clinical research and clinical care.

Placebo effects in randomized trials of pharmacological and neurostimulation interventions for mental disorders: An umbrella review

There is a growing literature exploring the placebo response within specific mental disorders, but no overarching quantitative synthesis of this research has analyzed evidence across mental disorders. We carried out an umbrella review of meta-analyses of randomized controlled trials (RCTs) of biological treatments (pharmacotherapy or neurostimulation) for mental disorders. We explored whether placebo effect size differs across distinct disorders, and the correlates of increased placebo effects. Based on a pre-registered protocol, we searched Medline, PsycInfo, EMBASE, and Web of Knowledge up to 23.10.2022 for systematic reviews and/or meta-analyses reporting placebo effect sizes in psychopharmacological or neurostimulation RCTs. Twenty meta-analyses, summarising 1,691 RCTs involving 261,730 patients, were included. Placebo effect size varied, and was large in alcohol use disorder (g = 0.90, 95% CI [0.70, 1.09]), depression (g = 1.10, 95% CI [1.06, 1.15]), restless legs syndrome (g = 1.41, 95% CI [1.25, 1.56]), and generalized anxiety disorder (d = 1.85, 95% CI [1.61, 2.09]). Placebo effect size was small-to-medium in obsessive-compulsive disorder (d = 0.32, 95% CI [0.22, 0.41]), primary insomnia (g = 0.35, 95% CI [0.28, 0.42]), and schizophrenia spectrum disorders (standardized mean change = 0.33, 95% CI [0.22, 0.44]). Correlates of larger placebo response in multiple mental disorders included later publication year (opposite finding for ADHD), younger age, more trial sites, larger sample size, increased baseline severity, and larger active treatment effect size. Most (18 of 20) meta-analyses were judged 'low' quality as per AMSTAR-2. Placebo effect sizes varied substantially across mental disorders. Future research should explore the sources of this variation. We identified important gaps in the literature, with no eligible systematic reviews/meta-analyses of placebo response in stress-related disorders, eating disorders, behavioural addictions, or bipolar mania.

Placebo and nocebo effects in gambling disorder pharmacological trials: a meta-analysis

BACKGROUND

Placebo and nocebo effects are widely reported across psychiatric conditions, yet have seldom been examined in the context of gambling disorder. Through meta-analysis, we examined placebo effects, their moderating factors, and nocebo effects, from available randomised, controlled pharmacological clinical trials in gambling disorder.

METHODS

We searched, up to 19 February 2024, a broad range of databases, for double-blind randomised controlled trials (RCTs) of medications for gambling disorder. Outcomes were gambling symptom severity and quality of life (for efficacy), and drop outs due to medication side effects in the placebo arms.

RESULTS

We included 16 RCTs (n = 833) in the meta-analysis. The overall effect size for gambling severity reduction in the placebo arms was 1.18 (95%CI 0.91-1.46) and for quality of life improvement was 0.63 (0.42-0.83). Medication class, study sponsorship, trial duration, baseline severity of gambling and publication year significantly moderated effect sizes for at least some of these outcome measures. Author conflict of interest, placebo run-in, gender split, severity scale choice, age of participants or unbalanced randomisation did not moderate effect sizes. Nocebo effects leading to drop out from the trial were observed in 6% of participants in trials involving antipsychotics, while this was less for other medication types.

CONCLUSION

Placebo effects in trials of pharmacological treatment of gambling disorder are large, and there are several moderators of this effect. Nocebo effects were measureable and may be influenced by medication class being studied. Practical implications of these new findings for the field are discussed, along with recommendations for future clinical trials.

Efficacy of medications for the treatment of alcohol use disorder (AUD): A systematic review and meta-analysis considering baseline AUD severity

Baseline severity of alcohol use disorder (AUD) is an influencing factor in the response to medications recommended for the treatment of AUD. The scarce efficacy of AUD medications partly justifies their limited uses. We were interested in evaluating the efficacy of approved and recommended AUD medications using generic inverse-variance, an analysis facilitating comparison between medications and placebo both at the end of the study and, concomitantly, to baseline values for the same participants. We conducted a systematic review to include randomized controlled trials (RCTs) comparing any medication to placebo providing, both at baseline and end of treatment, percent heavy drinking days (%HDD), percent drinking days (%DD), and/or drinks per drinking day (DDD). We searched PubMed, Embase, PMC, and three CT registers from inception to April 2023. A total of 79 RCTs (11,737 AUD participants; 30 different medications) were included: 47 RCTs (8465 participants) used AUD medications, and 32 RCTs (3272 participants) used other medications. At baseline, participants consumed on average approximately 12 DDD, and experienced 70 % DD, and 61 % HDD. Placebo halved or reduced these values to a third. Compared to placebo, AUD medications further reduced these outcomes (moderate to high certainty evidence). Other medications reduced the DDD without modifying other alcohol outcomes. AUD medications increased the risk of developing adverse events (high-certainty evidence). Despite the large placebo effects, our results support the benefits of providing AUD medications to people with AUD, helping them reduce alcohol consumption.

Assessment of treatment expectations in people with suspected endometriosis: A psychometric analysis

Background

Treatment expectations influence clinical outcomes in various physical and psychological conditions; however, no studies have explored their role in endometriosis treatment. It is necessary to understand how these expectations can be measured to study treatment expectations and their effects in clinical practice. This study aimed to psychometrically analyze and compare different treatment expectation measurements and describe treatment expectations in women with suspected endometriosis.

Method

Analysis of cross-sectional baseline data of a mixed-method clinical observational study of N=699 patients undergoing laparoscopy in Germany. Descriptives, bivariate associations, convergent and discriminant validity of four expectation measurements (Treatment Expectation Questionnaire (TEX-Q); Generic rating scale for previous treatment experiences, treatment expectations, and treatment effects (GEEE); numerical rating scales (NRS) assessing improvement and worsening of endometriosis symptoms, expected Pain Disability Index (PDI); range: 0 to 10) were estimated. A cluster analysis was performed on the three GEEE items.

Results

Most participants expected high improvement ( M=6.68 to 7.20, SD=1.90 to 2.09) and low worsening ( M=1.09 to 2.52, SD=1.80 to 2.25) of disability from laparoscopy. Participants who expected greater worsening expected more side effects ( r=.31 to .60, p<.001). Associations between the positive and negative expectation dimensions, including side effects, were small to non-significant ( r =|.24| to .00, p<.001 to.978). Four distinct clusters, described as'positive', 'no pain, no gain', 'diminished', and 'uniform' were found, with a total PVE of 62.2%.

Conclusions

Women with suspected endometriosis reported positive expectations concerning laparoscopy, but wide ranges indicated interindividual differences. Treatment expectations seem to be a multidimensional construct in this patient group. The investigated measurements did not correlate to the extent that they measured exactly the same construct. The selection of measurements should be carefully considered and adapted for the study purposes. Clusters provide initial indications for individualized interventions that target expectation manipulation.

Trial Registration Number

ID NCT05019612 ( ClinicalTrials.gov).

The absurdity of the latent disease model in mental health: 10,130,814 ways to have a DSM-5-TR psychological disorder

BACKGROUND

Latent disease classification is currently the accepted approach to mental illness diagnosis. In the United States, this takes the form of the Diagnostic and Statistical Manual of Mental Disorders-5-Text Revision (DSM-5-TR). Latent disease classification has been criticized for reliability and validity problems, particularly regarding diagnostic heterogeneity. No authors have calculated the scope of the heterogeneity problem of the entire DSM-5-TR.

AIMS

We addressed this issue by calculating the unique diagnostic profiles that exist for every DSM-5-TR diagnosis.

METHODS

We did this by applying formulas previously used in smaller heterogeneity analyses to all diagnoses within the DSM-5-TR.

RESULTS

We found that there are 10,130,814 ways to be diagnosed with a mental illness using DSM-5-TR criteria. When specifiers are considered, this number balloons to over 161 septillion unique diagnostic presentations (driven mainly by bipolar II disorder). Additionally, there are 1,951,065 ways to present with psychiatric symptoms, yet not meet diagnostic criteria.

CONCLUSIONS

Latent disease classification leads to considerable heterogeneity in possible presentations. We provide examples of how latent disease classification harms research and treatment programs. We echo recommendations for the dismissal of latent disease classification as a mental illness diagnostic program.

Ten years of maintenance treatment of severe melancholic depression in an adult woman including discontinuation experiences

BACKGROUND

There are only few publications on long-term treatments for major depressive disorder (MDD) lasting 5 years or longer. Most clinical controlled trials lasted no longer than 2 years and some recent studies suggested an advantage of cognitive behavioral therapy (CBT) over antidepressants in relapse prevention of MDD.

METHODS

Exclusively outpatient "real world" treatment of severe melancholia, prospectively documented over 10 years with different serial treatment strategies, discontinuation phenomena and complications.

METHODS

Compared to CBT, agomelatine, mirtazapine, bupropion and high-dose milnacipran, high-dose venlafaxine (extended-release form, XR) was effective, even sustainably. Asymptomatic premature ventricular contractions (PVCs) were found at the beginning of the treatment of the MDD, which initially led to the discontinuation of high-dose venlafaxine (300 mg daily). Even the various treatment strategies mentioned above were unable to compensate for or prevent the subsequent severe deterioration in MDD (2 rebounds, 1 recurrence). Only the renewed use of high-dose venlafaxine was successful. PVC no longer occurred and the treatment was also well tolerated over the years, with venlafaxine serum levels at times exceeding 5 times the recommended upper therapeutic reference level (known bupropion-venlafaxine interaction, otherwise 2.5 to 3-fold increase with high-dose venlafaxine alone). During dose reduction or after gradual discontinuation of high-dose venlafaxine, rather mild withdrawal symptoms occurred, but as described above, also two severe rebounds and one severe recurrence happened.

DISCUSSION

This long-term observation supports critical reflections on the discontinuation of successful long-term treatment with antidepressants in severe MDD, even if it should be under "the protection" of CBT. The PVC seemed to be more related to the duration of the severe major depressive episode than to the venlafaxine treatment itself. A particular prospective observation of this longitudinal case study is that relapses (in the sense of rebounds) during or after previous venlafaxine tapering seemed to herald the recurrence after complete recovery. Remarkably, neither relapses nor recurrence could be prevented by CBT.

CONCLUSION

In this case, high-dose venlafaxine has a particular relapse-preventive (and "recurrence-preventive") effect with good long-term tolerability.

Precision psychiatry: predicting predictability

Precision psychiatry is an emerging field that aims to provide individualized approaches to mental health care. An important strategy to achieve this precision is to reduce uncertainty about prognosis and treatment response. Multivariate analysis and machine learning are used to create outcome prediction models based on clinical data such as demographics, symptom assessments, genetic information, and brain imaging. While much emphasis has been placed on technical innovation, the complex and varied nature of mental health presents significant challenges to the successful implementation of these models. From this perspective, I review ten challenges in the field of precision psychiatry, including the need for studies on real-world populations and realistic clinical outcome definitions, and consideration of treatment-related factors such as placebo effects and non-adherence to prescriptions. Fairness, prospective validation in comparison to current practice and implementation studies of prediction models are other key issues that are currently understudied. A shift is proposed from retrospective studies based on linear and static concepts of disease towards prospective research that considers the importance of contextual factors and the dynamic and complex nature of mental health.

Working with patients' treatment expectations - what we can learn from homeopathy

The usual homeopathic remedy, "globules," does not contain any pharmacologically active ingredient. However, many patients and practitioners report beneficial effects of homeopathic treatment on various health outcomes. Experimental and clinical research of the last two decades analyzing the underlying mechanisms of the placebo effect could explain this phenomenon, with patients' treatment expectations as the predominant mechanism. Treatment expectations can be optimized through various factors, such as prior information, communication, and treatment context. This narrative review analyses how homeopathy successfully utilizes these factors. Subsequently, it is discussed what evidence-based medicine could learn from homeopathic practice to optimize treatment expectations (e.g., using an empathic, patient-centered communication style, deliberately selecting objects in practice rooms, or using clear treatment rituals and salient contextual stimuli) and thereby treatment effectiveness. Homeopathic remedy does not work beyond the placebo effect but is recommended or prescribed as an active treatment by those who believe in it. Thus, practitioners need to understand the manner in which homeopathy (as an example of inert treatment) works and are advised to reintegrate its underlying effective placebo mechanisms into evidence-based medicine. This promises to increase treatment efficacy, tolerability, satisfaction, and compliance with evidence-based treatments, and addresses the desires patients are trying to satisfy in homeopathy in an ethical, fully informed way that is grounded in evidence-based medicine.

Psychosocial and medication interventions to stop or reduce alcohol consumption during pregnancy

BACKGROUND

Despite the known harms, alcohol consumption is common in pregnancy. Rates vary between countries, and are estimated to be 10% globally, with up to 25% in Europe.

OBJECTIVES

To assess the efficacy of psychosocial interventions and medications to reduce or stop alcohol consumption during pregnancy.

SEARCH METHODS

We searched the Cochrane Drugs and Alcohol Group Specialised Register (via CRSLive), Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, CINAHL, Web of Science, and PsycINFO, from inception to 8 January 2024. We also searched for ongoing and unpublished studies via ClinicalTrials.gov and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). All searches included non-English language literature. We handsearched references of topic-related systematic reviews and included studies.

SELECTION CRITERIA

We included randomised controlled trials that compared medications or psychosocial interventions, or both, to placebo, no intervention, usual care, or other medications or psychosocial interventions used to reduce or stop alcohol use during pregnancy. Our primary outcomes of interest were abstinence from alcohol, reduction in alcohol consumption, retention in treatment, and women with any adverse event.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodological procedures.

MAIN RESULTS

We included eight studies (1369 participants) in which pregnant women received an intervention to stop or reduce alcohol use during pregnancy. In one study, almost half of participants had a current diagnosis of alcohol use disorder (AUD); in another study, 40% of participants had a lifetime diagnosis of AUD. Six studies took place in the USA, one in Spain, and one in the Netherlands. All included studies evaluated the efficacy of psychosocial interventions; we did not find any study that evaluated the efficacy of medications for the treatment of AUD during pregnancy. Psychosocial interventions were mainly brief interventions ranging from a single session of 10 to 60 minutes to five sessions of 10 minutes each. Pregnant women received the psychosocial intervention approximately at the end of the first trimester of pregnancy, and the outcome of alcohol use was reassessed 8 to 24 weeks after the psychosocial intervention. Women in the control group received treatment as usual (TAU) or similar treatments such as comprehensive assessment of alcohol use and advice to stop drinking during pregnancy. Globally, we found that, compared to TAU, psychosocial interventions may increase the rate of continuously abstinent participants (risk ratio (RR) 1.34, 95% confidence interval (CI) 1.14 to 1.57; I2 =0%; 3 studies; 378 women; low certainty evidence). Psychosocial interventions may have little to no effect on the number of drinks per day, but the evidence is very uncertain (mean difference -0.42, 95% CI -1.13 to 0.28; I2 = 86%; 2 studies; 157 women; very low certainty evidence). Psychosocial interventions probably have little to no effect on the number of women who completed treatment (RR 0.98, 95% CI 0.94 to 1.02; I2 = 0%; 7 studies; 1283 women; moderate certainty evidence). None of the included studies assessed adverse events of treatments. We downgraded the certainty of the evidence due to risk of bias and imprecision of the estimates.

AUTHORS' CONCLUSIONS

Brief psychosocial interventions may increase the rate of continuous abstinence among pregnant women who report alcohol use during pregnancy. Further studies should be conducted to investigate the efficacy and safety of psychosocial interventions and other treatments (e.g. medications) for women with AUD. These studies should provide detailed information on alcohol use before and during pregnancy using consistent measures such as the number of drinks per drinking day. When heterogeneous populations are recruited, more detailed information on alcohol use during pregnancy should be provided to allow future systematic reviews to be conducted. Other important information that would enhance the usefulness of these studies would be the presence of other comorbid conditions such as anxiety, mood disorders, and the use of other psychoactive substances.

Negative expectations (nocebo phenomenon) in clinical interventions: A scoping review

Unpredictable, undesirable, and confusing reactions in the face of psychological or medical interventions make the clinical presentation more complicated and may represent clinically unexplained symptoms and also disturbed the doctor-patients relationship and decrease patients' benefits of treatment. It seems that negative expectations from the treatment (nocebo phenomenon) can explain such reactions. The aim of the current study is a scoping review and investigate different aspects of the nocebo phenomenon (negative expectations) in clinical interventions. This paper follows a scoping review of the existence, importance, and multidimensions of the nocebo phenomenon in medical and psychological interventions. Data sources include literature databases (ProQuest, PubMed, Google Scholar, and Scopus) reviewed from inception dates to 2023, and the terms negative expectations, nocebo effect, placebo effect, negative placebo, and clinical interventions were searched. The review of the available articles showed that negative expectations play an important role in the process and effectiveness of clinical interventions. Negative expectations (here named nocebo effect) can significantly interfere with rapport and treatment processes. Some underlying components of the nocebo effect include negative expectancies, conditioning, social learning, memory, cognitive distortions, meaning, motivation, somatic focus, negative reinforcements, personality, anxiety, and neurophysiological factors such as CCK, dopamine, and cortisol are proposed for development and presence of nocebo phenomenon in clinical practice. Negative expectations with its biopsychosocial aspects play an important and amazing role in disorganizing medical and psychological interventions. Using appropriate methods to reduce nocebo effects in therapeutic interventions may increase treatment compliance and adherence and increase the effectiveness of interventions.

Probiotics Supplementation during Pregnancy: Can They Exert Potential Beneficial Effects against Adverse Pregnancy Outcomes beyond Gestational Diabetes Mellitus?

BACKGROUND

Probiotics, as supplements or food ingredients, are considered to exert promising healthy effects when administered in adequate quantity. Probiotics' healthy effects are related with the prevention of many diseases, as well as decreasing symptom severity. Currently, the most available data concerning their potential health effects are associated with metabolic disorders, including gestational diabetes mellitus. There is also clinical evidence supporting that they may exert beneficial effects against diverse adverse pregnancy outcomes. The purpose of the current narrative study is to extensively review and analyze the current existing clinical studies concerning the probable positive impacts of probiotics supplementation during pregnancy as a protective agent against adverse pregnancy outcomes beyond gestational diabetes mellitus.

METHODS

a comprehensive and thorough literature search was conducted in the most precise scientific databases, such as PubMed, Scopus, and Web of Sciences, utilizing efficient, representative, and appropriate keywords.

RESULTS

in the last few years, recent research has been conducted concerning the potential beneficial effects against several adverse pregnancy outcomes such as lipid metabolism dysregulation, gestational hypertensive disorders, preterm birth, excessive gestational weight gain, caesarean risk section, vaginal microbiota impairment, mental health disturbances, and others.

CONCLUSION

up to the present day, there is only preliminary clinical data and not conclusive results for probiotics' healthy effects during pregnancy, and it remains questionable whether they could be used as supplementary treatment against adverse pregnancy outcomes beyond gestational diabetes mellitus.

Placebo stimulates neuroplasticity in depression: implications for clinical practice and research

Neither psychological nor neuroscientific investigations have been able to fully explain the paradox that placebo is designed to be inert in randomized controlled trials (RCTs), yet appears to be effective in evaluations of clinical interventions in all fields of medicine and alternative medicine. This article develops the Neuroplasticity Placebo Theory, which posits that neuroplasticity in fronto-limbic areas is the unifying factor in placebo response (seen in RCTs) and placebo effect (seen in clinical interventions) where it is not intended to be inert. Depression is the disorder that has the highest placebo response of any medical condition and has the greatest potential for understanding how placebos work: recent developments in understanding of the pathophysiology of depression suggest that fronto-limbic areas are sensitized in depression which is associated with a particularly strong placebo phenomenon. An innovative linkage is made between diverse areas of the psychology and the translational psychiatry literature to provide supportive evidence for the Neuroplasticity Placebo Theory. This is underpinned by neuro-radiological evidence of fronto-limbic change in the placebo arm of antidepressant trials. If placebo stimulates neuroplasticity in fronto-limbic areas in conditions other than depression - and results in a partially active treatment in other areas of medicine - there are far reaching consequences for the day-to-day use of placebo in clinical practice, the future design of RCTs in all clinical conditions, and existing unwarranted assertions about the efficacy of antidepressant medications. If fronto-limbic neuroplasticity is the common denominator in designating placebo as a partially active treatment, the terms placebo effect and placebo response should be replaced by the single term "placebo treatment."

The Placebo Effect in Exercise and Mental Health Research

This chapter describes the placebo effect in the context of physical activity and mental health. Following a brief historical overview, definitions for placebos, placebo effects, and related terminology are discussed. Next, three major methodological challenges posed from studying the placebo effect in the context of exercise are described. Additionally, the role of a primary psychological mechanism of placebo and nocebo effects - expectations - will be summarized through the lens of key terminology. Findings from relevant chronic and acute exercise studies that have measured or manipulated exercise-associated expectations will be presented. The chapter concludes with recommendations for controlling or quantifying the placebo effect in exercise and mental health research and its implications in clinical practice.

A core component of psychological therapy causes adaptive changes in computational learning mechanisms

BACKGROUND

Cognitive distancing is an emotion regulation strategy commonly used in psychological treatment of various mental health disorders, but its therapeutic mechanisms are unknown.

METHODS

935 participants completed an online reinforcement learning task involving choices between pairs of symbols with differing reward contingencies. Half (49.1%) of the sample was randomised to a cognitive self-distancing intervention and were trained to regulate or 'take a step back' from their emotional response to feedback throughout. Established computational (Q-learning) models were then fit to individuals' choices to derive reinforcement learning parameters capturing clarity of choice values (inverse temperature) and their sensitivity to positive and negative feedback (learning rates).

RESULTS

Cognitive distancing improved task performance, including when participants were later tested on novel combinations of symbols without feedback. Group differences in computational model-derived parameters revealed that cognitive distancing resulted in clearer representations of option values (estimated 0.17 higher inverse temperatures). Simultaneously, distancing caused increased sensitivity to negative feedback (estimated 19% higher loss learning rates). Exploratory analyses suggested this resulted from an evolving shift in strategy by distanced participants: initially, choices were more determined by expected value differences between symbols, but as the task progressed, they became more sensitive to negative feedback, with evidence for a difference strongest by the end of training.

CONCLUSIONS

Adaptive effects on the computations that underlie learning from reward and loss may explain the therapeutic benefits of cognitive distancing. Over time and with practice, cognitive distancing may improve symptoms of mental health disorders by promoting more effective engagement with negative information.

Differential Placebo Responses for Pharmacotherapy and Neurostimulation in Late-Life Depression

BACKGROUND

The magnitude of the placebo response depends on both the modality used as the "placebo" and the intervention with which it is compared, both of which can complicate the interpretation of randomized controlled trials (RCTs) for depression in late life. Given that neurostimulation and pharmacotherapy are among the most common interventions studied for late-life depression, comparing the relative placebo responses in studies of these interventions can aid interpretation of relative effect sizes.

MATERIALS AND METHODS

We analyzed data from two RCTs of adults aged ≥60 years in an episode of treatment-resistant major depression, one comparing aripiprazole and matching placebo pills and the other comparing deep repetitive transcranial magnetic stimulation (rTMS) and sham rTMS. In both RCTs, depression was assessed using the 17-item Hamilton Depression Rating Scale (HDRS-17). The primary comparison occurred after four weeks using analysis of covariance (ANCOVA) of HDRS-17 scores in participants who received placebo pills or sham rTMS. Relevant covariates included years of education, duration of depressive episode, and baseline HDRS-17 score.

RESULTS

Accounting for covariates, there was a larger reduction of HDRS-17 after four weeks in the sham rTMS group (estimated marginal mean ± SE: -5.90 ± 1.45; 95% CI: [-8.82, 2.98]) than in the placebo pills group (-1.07 ± 1.45; [-3.98, 1.85]). There were no significant differences between these groups in the binary outcome analysis of response and remission rates at four weeks or any outcome at trial end point comparison.

CONCLUSIONS

Sham rTMS may have a larger placebo response than placebo pills early in the treatment of older adults with treatment-resistant depression. Differential placebo responses should be considered in both the interpretation and design of RCTs.

The 'placebo effect' in the conservative treatment of plantar fasciitis: a systematic review and meta-analyses

Purpose

The study of the placebo effect is key to elucidate the 'real effect' of conservative interventions for plantar fasciitis. The aim of this meta-analysis was to quantify the impact of placebo in the different conservative treatments of plantar fasciitis.

Methods

A systematic literature review was performed on double-blind placebo-controlled trials (RCTs) according to PRISMA guidelines on PubMed, Embase, and Web of Science. The meta-analysis primary outcome was the 0-10 pain variation after placebo treatments analyzed at 1 week, 1, 3, 6, and 12 months. The risk of bias was assessed using the RoB 2.0 tool, while the overall quality of evidence was graded according to the GRADE guidelines.

Results

The placebo effect for conservative treatments was studied in 42 double-blind RCTs on 1724 patients. The meta-analysis of VAS pain showed a statistically significant improvement after placebo administration of 2.13/10 points (P < 0.001), being highest at 12 months with 2.79/10 points (P < 0.001). The improvement of the placebo groups was higher in the extracorporeal shock wave therapy studies compared to the injection studies (2.59 vs 1.78; P = 0.05). Eight studies had a low risk of bias, 23 studies had 'some concerns,' and 4 studies had a high risk of bias. The GRADE evaluation showed an overall high quality of evidence.

Conclusion

This systematic review and meta-analysis demonstrated that the placebo effect represents an important component of all conservative approaches to treat plantar fasciitis. This effect is statistically and clinically significant, increases over time, and depends on the type of conservative treatment applied to address plantar fasciitis.

The Placebo Effect in Psychosis: Why It Matters and How to Measure It

Psychosis is characterized by unusual percepts and beliefs in the form of hallucinations and delusions. Antipsychotic medication, the primary treatment for psychosis, is often ineffective and accompanied by severe side effects, but research has not identified an effective alternative in several decades. One reason that clinical trials fail is that patients with psychosis tend to show a significant therapeutic response to inert control treatments, known as the placebo effect, which makes it difficult to distinguish drug effects from placebo effects. Conversely, in clinical practice, a strong placebo effect may be useful because it could enhance the overall treatment response. Identifying factors that predict large placebo effects could improve the future outlook of psychosis treatment. Biomarkers of the placebo effect have already been suggested in pain and depression, but not in psychosis. Quantifying markers of the placebo effect would have the potential to predict placebo effects in psychosis clinical trials. Furthermore, the placebo effect and psychosis may represent a shared neurocognitive mechanism in which prior beliefs are weighted against new sensory information to make inferences about reality. Examining this overlap could reveal new insights into the mechanisms underlying psychosis and indicate novel treatment targets. We provide a narrative review of the importance of the placebo effect in psychosis and propose a novel method to assess it.

Placebo effects in children with autism spectrum disorder

Placebo responses are frequently observed in research studies and clinical contexts, yet there is limited knowledge about the placebo effect among children with neurodevelopmental disorders. Here, we review the placebo effect in autism spectrum disorder (ASD). Placebo responses are widely evident in ASD clinical trials and could partly operate via so-called placebo-by-proxy, whereby caregivers or clinicians indirectly shape patient outcomes. Understanding the role of placebo effects in ASD may help discern genuine treatment effects from contextual factors in clinical trials. The much less studied nocebo effect, or negative placebo, might contribute to the experience of side effects in ASD treatments but empirical data is missing. Better knowledge about placebo and nocebo mechanisms may contribute to the development of more effective research designs, such as three-armed designs that account for natural history, and improved treatments for ASD symptoms. At a clinical level, deeper knowledge about placebo and nocebo effects may optimize the delivery of care for individuals with ASD in the future. WHAT THIS PAPER ADDS: Placebo responses are evident in autism spectrum disorder (ASD) clinical trials. Placebo responses in ASD are likely dependent on a placebo-by-proxy mechanism.

Systematic Review and Meta-Analysis of the Placebo Effect and its Correlates in Obsessive Compulsive Disorder

BACKGROUND

Obsessive-compulsive disorder (OCD) is a major mental health condition with a lifetime prevalence rate of 1.3% among adults. While placebo effects are well described for conditions such as depressive and anxiety disorders, they have not been systematically characterized in OCD.

OBJECTIVES

We aimed to determine the impact of placebos in improving different symptom domains in patients with OCD.

METHODS

We systematically searched PubMed, EMBASE, Scopus, Web of Science, Ovid, the Cochrane Library, and Google Scholar databases/search engine from inception to January 2021 for randomized controlled trials of treatments for OCD with a placebo arm. A modified Cohen's effect size (ES) was calculated using change in baseline to endpoint scores for different measurement scales within placebo arms to estimate placebo effects and to investigate their correlates by random-effects model meta-analyses.

RESULTS

Forty-nine clinical trials (placebo group n  =  1993), reporting 80 OCD specific (153 measures in general) were included in the analysis. Overall placebo ES (95% confidence interval [CI]) was 0.32 (0.22-0.41) on OCD symptoms, with substantial heterogeneity (I-square = 96.1%). Among secondary outcomes, general scales, ES: 0.27 (95%CI: 0.14-0.41), demonstrated higher ES than anxiety and depression scales, ES: 0.14 (95%CI: -0.4 to 0.32) and 0.05 (95%CI: -0.05 to 0.14), respectively. Clinician-rated scales, ES: 0.27(95%CI: 0.20-0.34), had a higher ES than self-reported scales, ES: 0.07 (95%CI: -0.08 to 0.22). More recent publication year, larger placebo group sample size, shorter follow-up duration, and younger age of participants were all associated with larger placebo ES. Egger's test reflected possible small-study effect publication bias (P  =  0.029).

CONCLUSION

Placebo effects are modest in OCD trials and are larger in clinician ratings, for younger patients, and early in the treatment course. These findings underscore the need for clinicians and scientists to be mindful of placebo effects when formulating treatments or research trials for OCD.

SYSTEMATIC REVIEW REGISTRATION NUMBER

PROSPERO CRD42019125979.

How Effective is a Web-Based Mental Health Intervention (Deprexis) in the Treatment of Moderate and Major Depressive Disorders when started during Routine Psychiatric Inpatient Treatment as an Adjunct Therapy? A Pragmatic Parallel-Group Randomized Controlled Trial

BACKGROUND

Internet-based self-help-programs like deprexis have been increasingly shown to reduce depressive symptoms if added to distinct, primarily outpatient-treatment-settings. There is limited information about the effectiveness of deprexis if started at routine psychiatric hospital inpatient treatment of moderate-to-severe major depressive disorder (MDD).

SUBJECTS AND METHODS

To examine, sixty-nine adult MDD-inpatients were randomly assigned to a 12-week-period of treatment-as-usual (TAU, N=33) or TAU plus guided deprexis (TAU-PLUS, N=36). The study was planned as a pragmatic approach considering psychiatric routine conditions, particularly, offering an instant and flexible discharge management when the patients felt stabilized enough for primary/secondary care. Therefore, there was no fixed time frame for the inpatient treatment duration. Post-discharge, patients were followed by structured telephone interviews up to study-endpoint, i. e., 12 weeks after deprexis-initiation. Primary (Beck-Depression-Inventory-II, BDI-II) and secondary outcome-measures (Hamilton-Depression-Scale, Clinical-Global-Impression-Severity, WHO-Well-Being-Index, Helping-Alliance-Questionnaire) were carried out at study entry and every 2 weeks. Furthermore, the working alliance with deprexis as well as the inpatient treatment duration, the daily activity and the utilization of post-hospital care after discharge were determined.

RESULTS

At week 12, modified ITT-analyses showed significant between-group differences of BDI-II scores in favor of the TAU-PLUS-patients (p=.03) corresponding to a medium effect size (d=-.73, 95% CI -1.4 to .06). TAU-PLUS-patients showed greater daily activity (p=.04, d=.70, 95% CI -.03 to 1.38) and had been discharged significantly earlier from inpatient treatment (p=.003). Post-discharge, the TAU-PLUS-group reported a lower rate of post-hospital care (p=.01) and re-admissions (p=.04). Secondary outcome-measures including the alliance with the therapists were not significantly different between the groups at study-endpoint. The patients´ working-alliance with deprexis significantly predicted MDD-improvement and wellbeing. Both groups (TAU and TAU plus deprexis) were comparable with regard to the prescribed antidepressant medication. Unfortunately, detailed data on the amount and actual duration of the psychotherapeutic and special therapeutic individual and group settings of the TAU were not collected CONCLUSION: TAU plus deprexis was superior to TAU in improving subjective depression-severity (BDI-II) and daily activity in patients having sought psychiatric inpatient MDD-treatment before. This beneficial effect appeared 12 weeks after inpatient deprexis-initiation, i. e. when the vast majority of patients were back in primary/secondary care. Adjunctive deprexis was associated with earlier discharges and a significant advantage for post-hospital stabilization. In this regard, it could be promising to include deprexis into inpatient treatment conditions, thereby also preparing its continuing outpatient use. We found no evidence that deprexis interfered negatively with the alliance between the patients and their therapists.

Mediators of Placebo Response to Cannabinoid Treatment in Children with Autism Spectrum Disorder

The placebo response has a substantial impact on treatment outcome. However, data regarding mediators of the placebo response in children with autism spectrum disorder (ASD) are sparse. This retrospective study investigated possible mediators of the placebo response among participants of a placebo-controlled trial of cannabinoid treatment for behavioral problems in children with ASD (CBA trial, age 5-21 years). We used a specifically designed questionnaire to explore possible mediators of the placebo response in 88 participants of the CBA trial who received a placebo and had valid outcome scores. The parents of 67 participants completed the questionnaire. The placebo response was positively associated with the child's comprehension of the treatment purpose (p = 0.037). There was also a trend for participants who had a relative aggravation of symptoms before treatment onset to improve following placebo treatment (p = 0.053). No other domains, including parental expectations, previous positive experience with similar treatments (behavioral conditioning), parental locus of control, quality of the patient-physician relationships, and adherence to study medications were associated with placebo-response. This finding suggests that efforts to explain the treatment purpose to children with disabilities may enhance treatment efficacy in clinical practice and decrease differences in the placebo response between study arms. Contrary to our hypothesis, parental expectations regarding cannabinoid treatment were not associated with the placebo response.

Predictors of placebo response in three large clinical trials of the V1a receptor antagonist balovaptan in autism spectrum disorder

High rates of placebo response are increasingly implicated in failed autism spectrum disorder (ASD) clinical trials. Despite this, there are limited investigations of placebo response in ASD. We sought to identify baseline predictors of placebo response and quantify their influence on clinical scales of interest for three harmonized randomized clinical trials of balovaptan, a V1a receptor antagonist. We employed a two-step approach to identify predictors of placebo response on the Vineland-II two-domain composite (2DC) (primary outcome and a caregiver measure) and Clinical Global Impression (CGI) scale (secondary outcome and a clinician measure). The initial candidate predictor set of variables pertained to participant-level, site-specific, and protocol-related factors. Step 1 aimed to identify influential predictors of placebo response using Least Absolute Shrinkage and Selection Operator (LASSO) regression, while Step 2 quantified the influence of predictors via linear regression. Results were validated through statistical bootstrapping approaches with 500 replications of the analysis dataset. The pooled participant-level dataset included individuals with ASD aged 5 to 62 years (mean age 21 [SD 10]), among which 263 and 172 participants received placebo at Weeks 12 and 24, respectively. Although no influential predictors were identified for CGI, findings for Vineland-II 2DC are robust and informative. Decreased placebo response was predicted by higher baseline Vineland-II 2DC (i.e., more advanced adaptive function), longer trial duration, and European (vs United States) sites, while increased placebo response was predicted by commercial (vs academic) sites, attention deficit hyperactivity disorder and depression. Identification of these factors may be useful in anticipating and mitigating placebo response in drug development efforts in ASD and across developmental and psychiatric conditions.

Usefulness of the placebo lead-in design for clinical trials with binary outcomes

BACKGROUND

In placebo-controlled clinical trials to develop new drugs for the treatment of psychiatric or neurological disorders, a high and sometimes greater-than-expected placebo response makes it difficult to show the superiority of an investigational drug over a corresponding placebo. To avoid such difficulty, a placebo lead-in design has been presented, but its usefulness has been open to discussion. Although the statistical properties of the placebo lead-in design are investigated in the context of continuous outcomes, whether these properties can be generalized for binary or ordinal cases remains unclear.

METHODS

We investigate whether the placebo lead-in design is useful in clinical trials with binary outcomes through mathematical formulae and a numerical investigation. Specifically, we compare the proportion of placebo responders, the drug-placebo difference, and the effect size between two populations: one enriched for placebo nonresponders and the other comprising the all-comers.

RESULTS

Under positive correlation of the data between the lead-in stage and the randomized stage for both treatment groups, we mathematically show that the proportion of responders in the population enriched for placebo nonresponders is less than that in the all-comers population, and whether the placebo lead-in design increases the drug-placebo difference depends on the variances of outcomes in both treatment groups as well as the correlations of the outcomes between two stages. Further, through a numerical investigation, we show that whether the placebo lead-in design increases the effect size strongly depends on the magnitude of the correlations and their difference.

CONCLUSION

If the correlation of the placebo-placebo group is much higher than that of the placebo-drug group, the placebo lead-in design is advantageous in most cases but has an impact on an estimand in placebo nonresponders. Therefore, we do not recommend using the placebo lead-in design for clinical trials with binary outcomes.

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."

Placebo response in pharmacological trials in patients with functional dyspepsia-A systematic review and meta-analysis

BACKGROUND

Pharmacological trials in functional dyspepsia (FD) are associated with high placebo response rates. We aimed to identify the magnitude and contributing factors to the placebo response.

METHODS

We conducted a systematic review and meta-analysis including randomized controlled trials (RCTs) with a dichotomous outcome in adult patients with FD that compared an active pharmacotherapeutic treatment with placebo. Our main outcome was identification of the magnitude of the pooled placebo response rate for the following endpoints: symptom responder, symptom-free responder, adequate relief responder, and combined endpoint responder (i.e., the primary endpoint of each specific trial regarding treatment response). Several putative moderators (i.e., patient, disease, and trial characteristics) were examined.

KEY RESULTS

We included 26 RCTs in our analysis. The pooled placebo response rate was 39.6% (95% CI 30.1-50.0) using the symptom responder definition, 20.5% (12.8-31.0) using the symptom-free responder definition, 38.5% (33.8-43.6) using the adequate relief responder definition, and 35.5% (31.6-39.7) using the combined endpoint responder definition. A lower overall baseline symptom score was significantly associated with a higher placebo response rate. No other moderators were found to significantly impact the placebo response rate. Due to the lack of data, no analyses could be performed according to individual FD subtypes or symptoms.

CONCLUSIONS AND INFERENCES

The pooled placebo response rate in pharmacological trials in FD is about 39%, depending on which responder definitions is used. Future trials should consider applying an entry criterion based on minimal level of symptom severity to decrease the placebo response. We also suggest separate reporting of core FD symptoms pending more concrete harmonization efforts in FD trials.

The future of psychopharmacology: a critical appraisal of ongoing phase 2/3 trials, and of some current trends aiming to de-risk trial programmes of novel agents

Despite considerable progress in pharmacotherapy over the past seven decades, many mental disorders remain insufficiently treated. This situation is in part due to the limited knowledge of the pathophysiology of these disorders and the lack of biological markers to stratify and individualize patient selection, but also to a still restricted number of mechanisms of action being targeted in monotherapy or combination/augmentation treatment, as well as to a variety of challenges threatening the successful development and testing of new drugs. In this paper, we first provide an overview of the most promising drugs with innovative mechanisms of action that are undergoing phase 2 or 3 testing for schizophrenia, bipolar disorder, major depressive disorder, anxiety and trauma-related disorders, substance use disorders, and dementia. Promising repurposing of established medications for new psychiatric indications, as well as variations in the modulation of dopamine, noradrenaline and serotonin receptor functioning, are also considered. We then critically discuss the clinical trial parameters that need to be considered in depth when developing and testing new pharmacological agents for the treatment of mental disorders. Hurdles and perils threatening success of new drug development and testing include inadequacy and imprecision of inclusion/exclusion criteria and ratings, sub-optimally suited clinical trial participants, multiple factors contributing to a large/increasing placebo effect, and problems with statistical analyses. This information should be considered in order to de-risk trial programmes of novel agents or known agents for novel psychiatric indications, increasing their chances of success.

Effects of intranasal oxytocin on neural reward processing in children and adolescents with reactive attachment disorder: A randomized controlled trial

Reactive attachment disorder (RAD) is associated with socially and emotionally withdrawn/inhibited behaviors and reduced neural responses to rewards. Children and adolescents with RAD show aberrant attachment behaviors, and existing psychotherapies are difficult to maintain; therefore, pharmacological interventions to aid and boost treatment responses are needed. Oxytocin (OT) administration is known to promote reward functioning. We investigated whether single-use intranasal OT administration improved neural responses during reward processing in patients with RAD compared with healthy controls. Twenty-four male children and adolescents with RAD (10-18 years old) and 27 age- and sex-matched typically developing individuals (10-17 years old) were included in this randomized, double-blind, placebo-controlled, cross-over, functional magnetic resonance imaging study. Following a single intranasal OT (24 IU) or placebo administration, neural responses were investigated using a monetary reward task. In the RAD group, OT significantly increased subjective motivation scores, significantly enhanced activation in the right middle frontal gyrus, and reduced activation in the right precentral gyrus during the monetary reward task. Additional analyses revealed increased activation in the bilateral caudate at a more lenient threshold. Under placebo conditions, the severity of internalizing problems in patients with RAD was negatively correlated with ventral striatal activity. Moreover, the effect of OT on ventral striatum activity was positively associated with the severity of internalizing problems in patients with RAD. Intranasal OT administration enhanced activity in the reward pathway in male children and adolescents with RAD, suggesting that exogenous OT promotes reward processing and reward-related motivational behavior in these individuals. Further investigation is needed to fully understand the neural mechanisms of intranasal OT and identify novel targets for pediatric cases with RAD. Clinical trial registration: UMIN-CTR; UMIN000013215. URL: https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000015419.

The effect of oxytocin nasal spray on social interaction in young children with autism: a randomized clinical trial

Early supports to enhance social development in children with autism are widely promoted. While oxytocin has a crucial role in mammalian social development, its potential role as a medication to enhance social development in humans remains unclear. We investigated the efficacy, tolerability, and safety of intranasal oxytocin in young children with autism using a double-blind, randomized, placebo-controlled, clinical trial, following a placebo lead-in phase. A total of 87 children (aged between 3 and 12 years) with autism received 16 International Units (IU) of oxytocin (n = 45) or placebo (n = 42) nasal spray, morning and night (32 IU per day) for twelve weeks, following a 3-week placebo lead-in phase. Overall, there was no effect of oxytocin treatment over time on the caregiver-rated Social Responsiveness Scale (SRS-2) (p = 0.686). However, a significant interaction with age (p = 0.028) showed that for younger children, aged 3-5 years, there was some indication of a treatment effect. Younger children who received oxytocin showed improvement on caregiver-rated social responsiveness ( SRS-2). There was no other evidence of benefit in the sample as a whole, or in the younger age group, on the clinician-rated Clinical Global Improvement Scale (CGI-S), or any secondary measure. Importantly, placebo effects in the lead-in phase were evident and there was support for washout of the placebo response in the randomised phase. Oxytocin was well tolerated, with more adverse side effects reported in the placebo group. This study suggests the need for further clinical trials to test the benefits of oxytocin treatment in younger populations with autism.Trial registration www.anzctr.org.au (ACTRN12617000441314).

An exploratory machine learning approach to identify placebo responders in pharmacological binge eating disorder trials

Randomized, placebo-controlled trials for binge eating disorder (BED) have revealed highly variable, and often marked, rates of short-term placebo response. Several quantitative based analyses in patients with BED have inconsistently demonstrated which patient factors attribute to an increase in placebo response. The objective of this study is to utilize machine learning (ML) algorithms to identify moderators of placebo response in patients with BED. Data were pooled from 12 randomized placebo-controlled trials evaluating different treatment options for BED. The final dataset consisted of 189 adults receiving placebo with complete information of baseline variables. Placebo responders were defined as patients experiencing ≥75% reduction in binge eating frequency (BEF) at study end point. Nine patient prerandomization variables were included as predictors. Patients were divided into training and testing subsets according to an 75%:25% distribution while preserving the proportion of placebo responders. All analysis was performed in the software Pumas 2.0. Gaussian Naïve Bayes algorithm showed the best cross-validation accuracy (~64%) and was chosen as the final algorithm. Shapley analysis suggested that patients with low baseline BEF and anxiety status were strong moderators of placebo response. Upon applying the final algorithm on the test dataset, the resulting sensitivity was 88% and prediction accuracy was 72%. This is the first application of ML to identify moderators of placebo response in BED. The results of this analysis confirm previous findings of lesser baseline disease severity and adds that patients with no anxiety are more susceptible to placebo response.

A Participant-Level Integrative Data Analysis of Differential Placebo Response for Suicidal Ideation and Nonsuicidal Depressive Symptoms in Clinical Trials of Intravenous Racemic Ketamine

BACKGROUND

Clinical trials of intravenous (IV) racemic (R,S)-ketamine (hereafter referred to as IV ketamine) have consistently reported rapid and substantial reductions in overall depressive symptoms compared with saline (inactive placebo) or midazolam (active placebo). The evidence for IV ketamine's specific effects on suicidal ideation is less clear, however. This study sought to examine whether differential placebo (saline or midazolam) response to overall depressive symptoms vs suicidal ideation may help explain these divergent findings.

METHODS

Data for this participant-level integrative data analysis were drawn from 151 participants across 10 studies, and linear regression was used to examine the relationship between placebo response for suicidal ideation vs other depressive symptoms indexed from standard rating scales-specifically, depressed mood, anhedonia, anxiety, and guilt-over time.

RESULTS

For participants receiving saline placebo (n = 46), greater placebo response was observed for suicidal ideation compared with other symptoms indexed from standard depression rating scales, except for anxiety. For those receiving midazolam placebo (n = 105), greater placebo response was observed for suicidal ideation compared with depressed mood or anhedonia, and no significant differences were observed when comparing suicidal ideation with anxiety or guilt.

CONCLUSIONS

Taken together, the results provide preliminary evidence of a differential placebo response for suicidal ideation vs other depressive symptoms, while anxiety and suicidal ideation appear to produce similar placebo response profiles. These findings may help explain the more modest findings in clinical IV ketamine trials for suicidal ideation than overall depression.

Can placebos reduce intrusive memories?

After traumatic experiences, intrusive memories can flash back and evoke significant distress. Here, we investigated whether the frequency and severity of intrusions can be reduced by the provision of placebo. After the (online) exposure to the trauma-film paradigm, healthy participants (N = 112) received deceptive placebo (DP), open-label placebo (OLP), or no treatment. In the DP group, participants were led to believe to receive a dopamine-modulating drug, which was supposed to disrupt the consolidation of traumatic memories, although they in fact received the same placebo tablets as the OLP group for one week. The results show that the groups did not differ in the frequency of intrusive memories after one week. However, participants receiving OLP reported a significantly reduced intensity of intrusions as compared to DP. Across groups, negative expectations about the intensity and controllability of intrusions were associated with a higher frequency of intrusions, higher distress, higher burden, and more negative appraisal. The results suggest that expectations play an important role in the emergence of intrusive memories and that some of the disabling aspects of intrusive memories can be reduced by placebo. This may carry clinical potential because placebos are an accessible, cost-effective intervention to reduce the risk of intrusive memories.

Expectation effects in working memory training

There is a growing body of research focused on developing and evaluating behavioral training paradigms meant to induce enhancements in cognitive function. It has recently been proposed that one mechanism through which such performance gains could be induced involves participants' expectations of improvement. However, no work to date has evaluated whether it is possible to cause changes in cognitive function in a long-term behavioral training study by manipulating expectations. In this study, positive or negative expectations about cognitive training were both explicitly and associatively induced before either a working memory training intervention or a control intervention. Consistent with previous work, a main effect of the training condition was found, with individuals trained on the working memory task showing larger gains in cognitive function than those trained on the control task. Interestingly, a main effect of expectation was also found, with individuals given positive expectations showing larger cognitive gains than those who were given negative expectations (regardless of training condition). No interaction effect between training and expectations was found. Exploratory analyses suggest that certain individual characteristics (e.g., personality, motivation) moderate the size of the expectation effect. These results highlight aspects of methodology that can inform future behavioral interventions and suggest that participant expectations could be capitalized on to maximize training outcomes.

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.

Influence of motivational placebo-related factors on the effects of exercise treatment in depressive adolescents

Recent meta-analyses reveal a moderate effect of physical activity (PA) in the treatment of adolescent depression. However, not only the underlying neurobiological mechanisms, also the influences of placebo-related motivational factors (beliefs and expectancies in sporting, enjoyment and prior sports experiences), are still unclear. Based on the data of our prior study "Mood Vibes", we hypothesized that placebo-inherent factors like positive prior sports experiences and motivational factors, (positive beliefs, expectancies, and enjoyment related to PA), would increase the effects of an add-on exercise-therapy in juvenile depression. From 64 included depressed adolescents, 41 underwent an intensive add-on PA-therapy. Motivational factors were assessed using sport-specific scales. The changes in depression scores under treatment were rated by self-rating scale (German "Childhood Depression Inventory", (DIKJ)). A mixed model for repeated measures (MMRM) was used to analyze the effects of the different motivational variates on DIKJ. While prior sports experiences had no impact, motivational factors showed a significant effect on PA-induced changes in DIKJ scores (p = 0.002). The demotivated participants improved less, whereas it was sufficient to be neutral towards sporting to benefit significantly more. Motivational placebo-related factors (beliefs, expectancies and enjoyment regarding PA) affected the outcomes of an exercise treatment in depressed adolescents. Yet, a neutral mindset was sufficient to profit more from PA. Prior sporting in the sense of positive conditioning and as a protective factor did not play a role. Knowledge about these influences could in a second step help to develop tailored therapies.

Daily mother-infant skin-to-skin contact and maternal mental health and postpartum healing: a randomized controlled trial

This randomized controlled trial examined the effects of a daily hour of mother-infant skin-to-skin contact (SSC) during the first five postnatal weeks, compared to care-as-usual, on maternal depressive (primary outcome), anxiety, stress, fatigue, pain, and delivery-related post-traumatic stress symptoms (PTSS). Prenatal symptom severity and touch discomfort were examined as moderators. Mothers and full-term infants were randomly allocated to SSC or care-as-usual conditions and followed during the first postnatal year. For the total group (intention-to-treat analyses), care-as-usual mothers showed an increase of anxiety symptoms from week 2 to 12, while SSC mothers displayed a stability of anxiety symptoms. Also, care-as-usual mothers showed an initial decrease in fatigue followed by an increase, while SSC mothers showed a decrease from week 2 to 12. In per-protocol analyses, including only the SSC dyads who adhered to SSC guidelines, findings on anxiety, but not fatigue, were replicated. No SSC effects were found for depressive, stress, and pain symptoms. No moderator, dose-response, or 52-week follow-up effects were found. PTSS were low with little variation; consequently, analyses were discontinued. Daily SSC in healthy mother-infant dyads may reduce anxiety and fatigue symptoms, but not depressive, stress, and pain symptoms, during the early postpartum period. Replication studies are recommended.

Control interventions in randomised trials among people with mental health disorders

BACKGROUND

Control interventions in randomised trials provide a frame of reference for the experimental interventions and enable estimations of causality. In the case of randomised trials assessing patients with mental health disorders, many different control interventions are used, and the choice of control intervention may have considerable impact on the estimated effects of the treatments being evaluated.

OBJECTIVES

To assess the benefits and harms of typical control interventions in randomised trials with patients with mental health disorders. The difference in effects between control interventions translates directly to the impact a control group has on the estimated effect of an experimental intervention. We aimed primarily to assess the difference in effects between (i) wait-list versus no-treatment, (ii) usual care versus wait-list or no-treatment, and (iii) placebo interventions (all placebo interventions combined or psychological, pharmacological, and physical placebos individually) versus wait-list or no-treatment. Wait-list patients are offered the experimental intervention by the researchers after the trial has been finalised if it offers more benefits than harms, while no-treatment participants are not offered the experimental intervention by the researchers.

SEARCH METHODS

In March 2018, we searched MEDLINE, PsycInfo, Embase, CENTRAL, and seven other databases and six trials registers.

SELECTION CRITERIA

We included randomised trials assessing patients with a mental health disorder that compared wait-list, usual care, or placebo interventions with wait-list or no-treatment .

DATA COLLECTION AND ANALYSIS

Titles, abstracts, and full texts were reviewed for eligibility. Review authors independently extracted data and assessed risk of bias using Cochrane's risk of bias tool. GRADE was used to assess the quality of the evidence. We contacted researchers working in the field to ask for data from additional published and unpublished trials. A pre-planned decision hierarchy was used to select one benefit and one harm outcome from each trial. For the assessment of benefits, we summarised continuous data as standardised mean differences (SMDs) and dichotomous data as risk ratios (RRs). We used risk differences (RDs) for the assessment of adverse events. We used random-effects models for all statistical analyses. We used subgroup analysis to explore potential causes for heterogeneity (e.g. type of placebo) and sensitivity analyses to explore the robustness of the primary analyses (e.g. fixed-effect model).

MAIN RESULTS

We included 96 randomised trials (4200 participants), ranging from 8 to 393 participants in each trial. 83 trials (3614 participants) provided usable data. The trials included 15 different mental health disorders, the most common being anxiety (25 trials), depression (16 trials), and sleep-wake disorders (11 trials). All 96 trials were assessed as high risk of bias partly because of the inability to blind participants and personnel in trials with two control interventions. The quality of evidence was rated low to very low, mostly due to risk of bias, imprecision in estimates, and heterogeneity. Only one trial compared wait-list versus no-treatment directly but the authors were not able to provide us with any usable data on the comparison. Five trials compared usual care versus wait-list or no-treatment and found a SMD -0.33 (95% CI -0.83 to 0.16, I² = 86%, 523 participants) on benefits. The difference between all placebo interventions combined versus wait-list or no-treatment was SMD -0.37 (95% CI -0.49 to -0.25, I² = 41%, 65 trials, 2446 participants) on benefits. There was evidence of some asymmetry in the funnel plot (Egger's test P value of 0.087). Almost all the trials were small. Subgroup analysis found a moderate effect in favour of psychological placebos SMD -0.49 (95% CI -0.64 to -0.30; I² = 53%, 39 trials, 1656 participants). The effect of pharmacological placebos versus wait-list or no-treatment on benefits was SMD -0.14 (95% CI -0.39 to 0.11, 9 trials, 279 participants) and the effect of physical placebos was SMD -0.21 (95% CI -0.35 to -0.08, I² = 0%, 17 trials, 896 participants). We found large variations in effect sizes in the psychological and pharmacological placebo comparisons. For specific mental health disorders, we found significant differences in favour of all placebos for sleep-wake disorders, major depressive disorder, and anxiety disorders, but the analyses were imprecise due to sparse data. We found no significant differences in harms for any of the comparisons but the analyses suffered from sparse data. When using a fixed-effect model in a sensitivity analysis on the comparison for usual care versus wait-list and no-treatment, the results were significant with an SMD of -0.46 (95 % CI -0.64 to -0.28). We reported an alternative risk of bias model where we excluded the blinding domains seeing how issues with blinding may be seen as part of the review investigation itself. However, this did not markedly change the overall risk of bias profile as most of the trials still included one or more unclear bias domains.

AUTHORS' CONCLUSIONS

We found marked variations in effects between placebo versus no-treatment and wait-list and between subtypes of placebo with the same comparisons. Almost all the trials were small with considerable methodological and clinical variability in factors such as mental health population, contents of the included control interventions, and outcome domains. All trials were assessed as high risk of bias and the evidence quality was low to very low. When researchers decide to use placebos or usual care control interventions in trials with people with mental health disorders it will often lead to lower estimated effects of the experimental intervention than when using wait-list or no-treatment controls. The choice of a control intervention therefore has considerable impact on how effective a mental health treatment appears to be. Methodological guideline development is needed to reach a consensus on future standards for the design and reporting of control interventions in mental health intervention research.

A generalized weighted combination test of treatment effect for clinical trials with a sequential parallel comparison design and binary endpoint

To address the issue of a large placebo effect in certain therapeutic areas, rather than the application of the traditional gold standard parallel group placebo-controlled design, different versions of the sequential parallel comparison design have been advocated. In general, the design consists of two consecutive stages and three treatment groups. Stage 1 placebo nonresponders potentially form a prespecified patient subgroup for formal between-treatment comparison at the final analysis. In this research, a version of the design is considered for a binary endpoint. To fully utilize all available data, a generalized weighted combination test is proposed in case placebo has a relatively small effect for some of the study endpoints. The weighted combination of the test based on stage 1 data and the test based on stage 2 data of stage 1 placebo nonresponders suggested in the literature uses only a part of the study data and is a special case of this generalized weighted combination test. A multiple imputation approach is outlined for handling missing not at random data. Simulation is conducted to evaluate the performances of the methods and a data example is employed to illustrate the applications of the methods.

Placebo effects and neuromodulation for depression: a meta-analysis and evaluation of shared mechanisms

There is growing evidence that placebo effects can meaningfully modulate the brain. However, there has been little consideration of whether these changes may overlap with regions/circuits targeted by depression treatments and what the implications of this overlap would be on measuring efficacy in placebo-controlled clinical trials. In this systematic review and meta-analysis, we searched PubMed/Medline and Google Scholar for functional MRI and PET neuroimaging studies of placebo effects. Studies recruiting both healthy subjects and patient populations were included. Neuroimaging coordinates were extracted and included for Activation Likelihood Estimation (ALE) meta-analysis. We then searched for interventional studies of transcranial magnetic stimulation (TMS) and deep brain stimulation (DBS) for depression and extracted target coordinates for comparative spatial analysis with the placebo effects maps. Of 1169 articles identified, 34 neuroimaging studies of placebo effects were included. There were three significant clusters of activation: left dorsolateral prefrontal cortex (DLPFC) (x = -41, y = 16, z = 34), left sub-genual anterior cingulate cortex (sgACC)/ventral striatum (x = -8, y = 18, z = -15) and the right rostral anterior cingulate cortex (rACC) (x = 4, y = 42, z = 10). There were two significant deactivation clusters: right basal ganglia (x = 20, y = 2, z = 7) and right dorsal anterior cingulate cortex (dACC) (x = 1, y = -5, z = 45). TMS and DBS targets for depression treatment overlapped with the left DLPFC cluster and sgACC cluster, respectively. Our findings identify a common set of brain regions implicated in placebo effects across healthy individuals and patient populations, and provide evidence that these regions overlap with depression treatment targets. We model the statistical impacts of this overlap and demonstrate critical implications on measurements of clinical trial efficacy for this field.

Clinical effects of glabellar botulinum toxin injections on borderline personality disorder: A randomized controlled trial

BACKGROUND

Inhibition of frowning via injections of botulinum toxin A (BTX) into the glabellar region has shown beneficial effects in the treatment of major depression. Preliminary research suggests that improvements in the affective domain are not depression-specific, but may also translate to other psychiatric disorders.

AIM

This 16-week, single-blind, two-center randomized controlled trial investigated the influence of BTX on clinical symptoms of borderline personality disorder (BPD).

METHODS

Fifty-four patients with BPD were randomly assigned to treatment with BTX (n = 27) or a minimal acupuncture (ACU) control condition (n = 27). Clinical outcomes were followed at 2, 4, 6, 8, 12, and 16 weeks. Primary endpoint was the relative score change on the Zanarini Rating Scale for Borderline Personality Disorder (ZAN-BPD) 8 weeks after baseline relative to the control group and adjusted for treatment center. Secondary and additional outcome variables were self-rated borderline symptoms, comorbid symptoms of depression, psychological distress, and clinical global impression.

RESULTS

Participants showed significant improvements at the primary efficacy endpoint in both treatment groups (BTX: M = -0.39, SD = 0.39; ACU: M = -0.35, SD = 0.42), but no superior effect of the BTX condition in comparison with the control intervention was found-F(1,5323) = 0.017, p = 0.68). None of the secondary or additional outcomes yielded significant group differences. Side effects were mild and included headache, transient skin or muscle irritations, and dizziness.

CONCLUSION

Evidence regarding the efficacy of BTX for BDP remains limited, and the design of adequate control conditions presents an opportunity for further research.ClinicalTrials.gov registry: Botulinum Toxin A for Emotional Stabilization in Borderline Personality Disorder (BPD), NCT02728778, https://clinicaltrials.gov/ct2/show/NCT02728778.

Placebo response with subcutaneous injections in calcitonin gene-related peptide receptor monoclonal antibody migraine preventative trials – A systematic review and meta-analysis

Background:

The majority of CGRP monoclonal antibodies for migraine prevention are administered subcutaneously. Therefore, we attempted to calculate the pooled placebo response with subcutaneous placebo injections in this systematic review and meta-analysis.

Methods:

We identified 16 randomized controlled trials that met our inclusion and exclusion criteria through a comprehensive search in five electronic databases (PubMed Central, EMBASE, MEDLINE, Cochrane library and clinicaltrials.gov ). The risk of bias was assessed for all included studies. Random effects model was used to calculate pooled mean monthly migraine days and 50% response rates.

Results:

A total of 4240 subjects were included from 16 studies in this meta-analysis. The pooled mean monthly migraine day reduction with subcutaneous placebo injections was 2.15 (95% CI: 1.60–2.69). The pooled proportion of patients achieving a 50% reduction in mean monthly headache days was 26% (95% CI: 20%–31%). Placebo response accounted for more than 50% of therapeutic gain in our study.

Conclusion:

A substantial placebo response was noted with subcutaneous injections in migraine CGRP monoclonal antibody clinical trials. This meta-analysis may serve as a reference point to calculate sample size in clinical trials using subcutaneous interventions for migraine prevention. We registered our study at PROSPERO (CRD42020185300).

Placebos in Schizophrenia Research: An Historical Overview and Introduction to Ethical Issues

This short introduction provides a historical and ethical overview of placebos and placebo controls in relation to schizophrenia research, with a focus on long-term clinical trials. Drawing on historical and philosophical scholarship, it sketches a two-level analysis of ethical issues that placebos and the placebo effect raise for the field, particularly in light of shifts in clinical trial methodologies and clinical practices.

Using Artificial Intelligence-based Methods to Address the Placebo Response in Clinical Trials

The placebo response is a highly complex psychosocial-biological phenomenon that has challenged drug development for decades, particularly in neurological and psychiatric disease. While decades of research have aimed to understand clinical trial factors that contribute to the placebo response, a comprehensive solution to manage the placebo response in drug development has yet to emerge. Advanced data analytic techniques, such as artificial intelligence (AI), might be needed to take the next leap forward in mitigating the negative consequences of high placebo-response rates. The objective of this review was to explore the use of techniques such as AI and the sub-discipline of machine learning (ML) to address placebo response in practical ways that can positively impact drug development. This examination focused on the critical factors that should be considered in applying AI and ML to the placebo response issue, examples of how these techniques can be used, and the regulatory considerations for integrating these approaches into clinical trials.

The Importance of Patient Expectations: A Mixed-Methods Study of U.S. Psychiatrists

Objective: To examine how psychiatrists think about and modulate non-specific factors (e.g., hope, expectations) in clinical practice. Methods: U.S. psychiatrists were recruited for two studies assessing attitudes and behaviors related to non-specific factors. Study 1 entailed remote qualitative focus groups (k = 7) with n = 26 participants (36.0% female). Study 2 was a quantitative survey with n = 346 respondents (34.0% female) designed to assess the generalizability of focus group findings. Results: Four themes were identified in Study 1 that were used to inform the survey (Study 2): (1) Expectations (2) Hope, (3) Placebo Effect, and (4) Aesthetic Features. Nearly all surveyed psychiatrists (92.2%) considered patient expectations at least "most of the time" when interacting with a patient. Focus groups revealed that psychiatrists often attempt to balance optimism and realism to improve outcomes. A majority of survey respondents believed office design and physician attire could at least somewhat influence expectations (72.5 and 77.3%, respectively) and even outcomes (51.5 and 58.7%, respectively). Focus group psychiatrists described how physical features may be used as therapeutic tools. Conclusions: Psychiatrists are highly mindful of patient expectations. Although there is variability in the perceived importance of expectations, hope, the placebo effect, and aesthetic features, many utilize these factors in clinical practice.

Intermittent theta burst stimulation of cerebellar vermis enhances fronto-cerebellar resting state functional connectivity in schizophrenia with predominant negative symptoms: A randomized controlled trial

OBJECTIVE

Negative symptoms of schizophrenia are substantially disabling and treatment resistant. Novel treatments like repetitive transcranial magnetic stimulation (TMS) need to be examined for the same using the experimental medicine approach that incorporates tests of mechanism of action in addition to clinical efficacy in trials.

METHODS

Study was a double-blind, parallel, randomized, sham-controlled trial recruiting schizophrenia with at least a moderate severity of negative symptoms. Participants were randomized to real or sham intermittent theta burst stimulation (iTBS) under MRI-guided neuro-navigation, targeting the cerebellar vermis area VII-B, at a stimulus intensity of 100% active motor threshold, two sessions/day for five days (total = 6000 pulses). Assessments were conducted at baseline (T0), day-6 (T1) and week-6 (T2) after initiation of intervention. Main outcomes were, a) Scale for the Assessment of Negative Symptoms (SANS) score (T0, T1, T2), b) fronto-cerebellar resting state functional connectivity (RSFC) (T0, T1).

RESULTS

Thirty participants were recruited in each arm. Negative symptoms improved in both arms (p < 0.001) but was not significantly different between the two arms (p = 0.602). RSFC significantly increased between the cerebellar vermis and the right inferior frontal gyrus (p_cluster-FWER = 0.033), right pallidum (p_cluster-FWER = 0.042) and right frontal pole (p_cluster-FWER = 0.047) in the real arm with no change in the sham arm.

CONCLUSION

Cerebellar vermal iTBS engaged a target belonging to the class of cerebello-subcortical-cortical networks, implicated in negative symptoms of schizophrenia. However, this did not translate to a superior clinical efficacy. Future trials should employ enhanced midline cerebellar TMS stimulation parameters for longer durations that can potentiate and translate biological changes into clinical effects.

Differential power of placebo across major psychiatric disorders: a preliminary meta-analysis and machine learning study

The placebo effect across psychiatric disorders is still not well understood. In the present study, we conducted meta-analyses including meta-regression, and machine learning analyses to investigate whether the power of placebo effect depends on the types of psychiatric disorders. We included 108 clinical trials (32,035 participants) investigating pharmacological intervention effects on major depressive disorder (MDD), bipolar disorder (BD) and schizophrenia (SCZ). We developed measures based on clinical rating scales and Clinical Global Impression scores to compare placebo effects across these disorders. We performed meta-analysis including meta-regression using sample-size weighted bootstrapping techniques, and machine learning analysis to identify the disorder type included in a trial based on the placebo response. Consistently through multiple measures and analyses, we found differential placebo effects across the three disorders, and found lower placebo effect in SCZ compared to mood disorders. The differential placebo effects could also distinguish the condition involved in each trial between SCZ and mood disorders with machine learning. Our study indicates differential placebo effect across MDD, BD, and SCZ, which is important for future neurobiological studies of placebo effects across psychiatric disorders and may lead to potential therapeutic applications of placebo on disorders more responsive to placebo compared to other conditions.

Dr. Sprengers et al. Reply

Before we elaborate on the postulated discrepancies between our trial and previous bumetanide in autism spectrum disorder (ASD) trials, we would like to acknowledge the crucial pioneering work on the γ-aminobutyric acid (GABA) developmental sequence by Dr. Ben-Ari and colleagues. Chloride dysregulation and altered GABA polarity have been implicated in neurological and neurodevelopmental disorders, including some forms of ASD. Etiologies underlying ASD are profoundly heterogeneous, and an important challenge is to link the optimal treatment to individual patients. Indeed, ASD animal models indicate reversed GABA polarity as a treatment target in some,^1,2 but not all, studies.³ The aim of the Bumetanide in Autism Medication and Biomarker (BAMBI) trial was to replicate previous trial findings and to develop stratification biomarkers that may help to understand expected variability in treatment response.

Underpredicting pain: an experimental investigation into the benefits and risks

ABSTRACT

Expectancies can shape pain and other experiences. Generally, experiences change in the direction of what is expected (ie, assimilation effects), as seen with placebo effects. However, in case of large expectation-experience discrepancies, experiences might change away from what is expected (ie, contrast effects). Previous research has demonstrated contrast effects on various outcomes, but not pain. We investigated the effects of strong underpredictions of pain on experienced pain intensity. In addition, we assessed related outcomes including (certainty of) expectations, fear of pain, pain unpleasantness, autonomic responses, and trust. Healthy participants (study 1: n = 81 and study 2: n = 123) received verbal suggestions that subsequent heat stimuli would be moderately or highly painful (correct prediction), mildly painful (medium underprediction; study 2 only), or nonpainful (strong underprediction). Both studies showed that participants experienced less intense pain upon strong underprediction than upon correct prediction (ie, assimilation). Expected pain, fear of pain, and pain unpleasantness were generally also lowered. However, strong underprediction simultaneously lowered certainty of expectations and trust in the experimenter. Study 2 indicated that the effects of strong underprediction vs medium underprediction generally did not differ. Moreover, study 2 provided some indications for reduced heart rate and skin conductance levels but increased skin conductance responses upon strong underprediction. In conclusion, even strong underpredictions of pain can reduce pain (ie, cause assimilation), although not significantly more than medium underpredictions. However, strong underpredictions can cause uncertainty and undermine trust. These findings suggest that healthcare providers may wish to be cautious with providing overly positive information about painful medical procedures.