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

ABSTRACT: Background:There is debate in the literature as to whether inclusion of a placebo arm may alter characteristics of antidepressant trials. However, previous research has focused on response rates of various antidepressants on average only, ignoring potential differences among drugs or other aspects of trial findings. Little is known about the impact of a placebo arm on all-cause dropout and dropout due to adverse events. Methods:We carried out a systematic review of published and unpublished double-blind randomized controlled trials (RCTs) for the acute treatment of unipolar major depression (update: January 2016). The probability of being allocated to placebo (?) was the exposure of interest, and we examined its influence on responders (efficacy), all-cause dropouts (acceptability) and dropouts due to adverse events (tolerability), while accounting for differences in drugs, trials and patient characteristics in multivariate random effects meta-regression. Results:We included 421 studies (68 305 participants) comparing 16 antidepressants or placebo; ? ranged from 20% to 50%. Response rate was lower [risk ratio (RR) 0.87; 95% confidence interval (CI) 0.83, 0.92] and all-cause dropout rate higher (RR 1.19; 95% CI 1.08, 1.31) for the same antidepressants in placebo-controlled trials compared with head-to-head trials. The probability of responding decreased by 3% (95% CI 2-5%) for every 10% increase in ?, whereas the risk of all-cause dropout increased by 4% (95% CI 1-7%). Tolerability was unaffected by ?. Response rate was inversely correlated with dropouts due to any cause (correlation coefficient -0.48; 95% CI -0.58, -0.36) and due to adverse events (-0.34; 95% CI -0.44, -0.23). Conclusions:For the same antidepressant, response rate was on average smaller and dropouts higher when placebo was included; however, no association was found with dropouts due to adverse events. Decreased patient expectations, larger dropout rates and use of inappropriate statistical methods to impute missing data may explain this phenomenon. The findings call for caution in the integration of randomized evidence involving placebo arms.

SUBMITTER: Salanti G

PROVIDER: S-EPMC6208275 | biostudies-other | 2018 Oct

REPOSITORIES: biostudies-other

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

Salanti Georgia G Chaimani Anna A Furukawa Toshi A TA Higgins Julian P T JPT Ogawa Yusuke Y Cipriani Andrea A Egger Matthias M

International journal of epidemiology 20181001 5

<h4>Background</h4>There is debate in the literature as to whether inclusion of a placebo arm may alter characteristics of antidepressant trials. However, previous research has focused on response rates of various antidepressants on average only, ignoring potential differences among drugs or other aspects of trial findings. Little is known about the impact of a placebo arm on all-cause dropout and dropout due to adverse events.<h4>Methods</h4>We carried out a systematic review of published and u ...[more]

PMID: 29878123

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Project description:ImportanceAdverse events (AEs) after placebo treatment are common in randomized clinical drug trials. Systematic evidence regarding these nocebo responses in vaccine trials is important for COVID-19 vaccination worldwide especially because concern about AEs is reported to be a reason for vaccination hesitancy.ObjectiveTo compare the frequencies of AEs reported in the placebo groups of COVID-19 vaccine trials with those reported in the vaccine groups.Data sourcesFor this systematic review and meta-analysis, the Medline (PubMed) and Cochrane Central Register of Controlled Trials (CENTRAL) databases were searched systematically using medical subheading terms and free-text keywords for trials of COVID-19 vaccines published up to July 14, 2021.Study selectionRandomized clinical trials of COVID-19 vaccines that investigated adults aged 16 years or older were selected if they assessed solicited AEs within 7 days of injection, included an inert placebo arm, and provided AE reports for both the vaccine and placebo groups separately. Full texts were reviewed for eligibility by 2 independent reviewers.Data extraction and synthesisData extraction and quality assessment were performed independently by 2 reviewers, adhering to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guideline and using the Cochrane risk-of-bias tool. Meta-analyses were based on random-effects models.Main outcomes and measuresThe primary outcomes were the proportions of placebo recipients reporting overall, systemic, and local (injection-site) AEs as well as logarithmic odds ratios (ORs) to evaluate group differences. Outcomes were tested for significance using z tests with 95% CIs.ResultsTwelve articles with AE reports for 45 380 participants (22 578 placebo recipients and 22 802 vaccine recipients) were analyzed. After the first dose, 35.2% (95% CI, 26.7%-43.7%) of placebo recipients experienced systemic AEs, with headache (19.3%; 95% CI, 13.6%-25.1%) and fatigue (16.7%; 95% CI, 9.8%-23.6%) being most common. After the second dose, 31.8% (95% CI, 28.7%-35.0%) of placebo recipients reported systemic AEs. The ratio between placebo and vaccine arms showed that nocebo responses accounted for 76.0% of systemic AEs after the first COVID-19 vaccine dose and for 51.8% after the second dose. Significantly more vaccine recipients reported AEs, but the group difference for systemic AEs was small after the first dose (OR, -0.47; 95% CI, -0.54 to -0.40; P < .001; standardized mean difference, -0.26; 95% CI, -0.30 to -0.22) and large after the second dose (OR, -1.36; 95% CI, -1.86 to -0.86; P < .001; standardized mean difference, -0.75; 95% CI, -1.03 to -0.47).Conclusions and relevanceIn this systematic review and meta-analysis, significantly more AEs were reported in vaccine groups compared with placebo groups, but the rates of reported AEs in the placebo arms were still substantial. Public vaccination programs should consider these high rates of AEs in placebo arms.

Project description:Objective: To identify predictors of medication-placebo differences in double-blind placebo-controlled antidepressant trials in children and adolescents with anxiety and depression. Methods: Clinical trials in patients <18 years of age with major depressive disorder or generalized, separation or social anxiety disorders were obtained from PubMed, the Cochrane Database and clinicaltrials.gov searches from inception through 2019. Forty-nine trials (43 published and 6 unpublished) of anxiety (κ = 13) and depression (κ = 36) evaluated 19 antidepressants in 8642 child and adolescent patients; placebo and medication response rates, trial characteristics, disorder, medication class, and funding source were extracted. Antidepressant-placebo differences were examined using Bayesian hierarchical models and estimates of response were determined for trial design, disorder, and medication class variables. Using meta-regression, correlates of antidepressant-placebo difference and placebo response were examined. Results: Funding source differentiated medication-placebo differences regardless of disorder. Industry trials had larger placebo response rates (mean difference: 0.189 ± 0.066, credible interval [CrI]: 0.067 to 0.33, p = 0.0008) and smaller medication-placebo differences (-0.235 ± 0.078, CrI: -0.397 to -0.086, p = 0.005) compared with federally funded trials. However, medication response was similar for industry- and federally-funded studies (-0.046 ± 0.042, CrI: -0.130 to 0.038, p = 0.252). Conclusions: The impact of study sponsorship on trial outcome supports the assertion that industry-funded trials with high placebo response rates and small drug-placebo differences are "failed trials" and should not be described as "negative trials" or used to determine public health estimates of antidepressant efficacy in children and adolescents with anxiety and depression. Identifying the proper role and value of industry-funded trials is critical to establishing the evidence base for antidepressants in youth.

Project description:BackgroundChronic painful conditions have an important influence on the ability to work. Work-related outcomes, however, are not commonly reported in publications on trials investigating the treatment of chronic painful conditions. We aim to provide an overview of the reporting of work-related outcomes in such trials and investigate the relationship between work-related outcomes and pain outcomes.MethodsWe conducted a systematic literature search in PubMed with the aim of identifying randomised placebo-controlled clinical trials investigating treatments for chronic painful conditions or rheumatic diseases that also reported on work-related outcomes. Methodological study quality was assessed with the Oxford Quality Scale (OQS). Meta-analyses were conducted for the outcomes of interference with work and number of patients with at least 30% reduction in pain intensity (30% pain responders). The correlation between work-related and pain outcomes was investigated with regression analyses.ResultsWe included 31 publications reporting on 27 datasets from randomised placebo-controlled trials (with a total of 11,434 study participants) conducted in chronic painful or rheumatic diseases and reporting on work-related outcomes. These 31 publications make up only about 0.2% of all publications on randomised placebo-controlled trials in such conditions. The methodological quality of the included studies was high; only nine studies scored less than four (out of a maximum five) points on the OQS. Sixteen different work-related outcomes were reported on in the studies. Of 25 studies testing for the statistical significance of changes in work-related outcomes over the course of the trials, 14 (56%) reported a significant improvement; the others reported non-significant changes. Eight studies reported data on both interference with work and 30% pain responders: meta-analyses demonstrated similar, statistically significant improvements in both these outcomes with active therapy compared to placebo and regression analysis showed that these outcomes were correlated.ConclusionsDespite the importance of pain as a reason for decreased ability to work, work-related outcomes are reported in substantially less than 1% of publications on placebo-controlled trials in chronic painful and rheumatic diseases. Work-related outcomes and pain responder outcomes are closely related.

Project description:BackgroundPlacebo response in autism spectrum disorder (ASD) might dilute drug-placebo differences and hinder drug development. Therefore, this meta-analysis investigated placebo response in core symptoms.MethodsWe searched ClinicalTrials.gov , CENTRAL, EMBASE, MEDLINE, PsycINFO, WHO-ICTRP (up to July 8, 2018), and PubMed (up to July 4, 2019) for randomized pharmacological and dietary supplement placebo-controlled trials (RCTs) with a minimum of seven days of treatment. Single-group meta-analyses were conducted using a random-effects model. Standardized mean changes (SMC) of core symptoms in placebo arms were the primary outcomes and placebo positive response rates were a secondary outcome. Predictors of placebo response were investigated with meta-regression analyses. The protocol was registered with PROSPERO ID CRD42019125317 .ResultsEighty-six RCTs with 2360 participants on placebo were included in our analysis (87% in children/adolescents). The majority of trials were small, single-center with a duration of 8-12 weeks and published after 2009. Placebo response in social-communication difficulties was SMC = - 0.32, 95% CI [- 0.39, - 0.25], in repetitive behaviors - 0.23[- 0.32, - 0.15] and in scales measuring overall core symptoms - 0.36 [- 0.46, - 0.26]. Overall, 19%, 95% CI [16-22%] of participants were at least much improved with placebo. Caregiver (vs. clinician) ratings, lower risk of bias, flexible-dosing, larger sample sizes and number of sites, less recent publication year, baseline levels of irritability, and the use of a threshold of core symptoms at inclusion were associated with larger placebo response in at least a core symptom domain.LimitationsAbout 40% of the trials had an apparent focus on core symptoms. Investigation of the differential impact of predictors on placebo and drug response was impeded by the use of diverse experimental interventions with essentially different mechanisms of action. An individual-participant-data meta-analysis could allow for a more fine-grained analysis and provide more informative answers.ConclusionsPlacebo response in ASD was substantial and predicted by design- and participant-related factors, which could inform the design of future trials in order to improve the detection of efficacy in core symptoms. Potential solutions could be the minimization and careful selection of study sites as well as rigorous participant enrollment and the use of measurements of change not solely dependent on caregivers.

Project description:BackgroundThe effectiveness of nonsurgical treatment of patellar tendinopathy is questioned due to the conflicting results of placebo-controlled randomized controlled trials (RCTs) in which placebo arms often show impressive results.PurposeTo quantify the magnitude of placebo effect of the different nonsurgical treatments of patellar tendinopathy. We also evaluated the influence of patients and treatments characteristics on the response to the placebo.Study designSystematic review; Level of evidence, 1.MethodsWe searched PubMed, Web of Science, Embase, Scopus, Cochrane Library, and gray literature databases on May 10, 2023, with no time limitation. RCTs on nonoperative treatment of patellar tendinopathy, including a placebo control arm reporting the evolution of symptoms after placebo administration, were included. A single-arm meta-analysis was performed with the Victorian Institute of Sport Assessment-Patella (VISA-P) at mid-term follow-up (3-6 months) as the primary outcome. The VISA-P score at short-term (1-3 months) and long-term (6-12 months) follow-ups, as well as visual analog scale (VAS) for pain at all 3 time points were also analyzed. A subanalysis based on the type of placebo and a meta-regression were conducted to look for potential determinants of the placebo effect. Risk of bias and level of evidence were also analyzed using the revised tool for risk of bias in randomized trials and Grading of Recommendations Assessment, Development and Evaluation.ResultsIn total, 14 studies (251 patients) were included. VISA-P score at mid-term follow-up (3-6 months) showed statistically significant improvements of 13 of 100 points (P = .001). The change at short-term follow-up (1-3 months) was not statistically significant, whereas at long-term follow-up (6-12 months) it was 27 of 100 points (P < .001). Regarding VAS, results were statistically significant only at mid-term (MD = -1.5/10; P = .02) and long-term (MD = -3.2/10; P < .001) follow-ups. The meta-regression showed positive correlations between the response to placebo and the follow-up length (P < .001) and the effect size in the experimental group (P = .006). The level of evidence was moderate for mid- and long-term results and low for short-term results.ConclusionThe placebo effect for nonsurgical treatments of patellar tendinopathy is long-lasting (up to 12 months) and statistically and clinically significant. It has a perceived and true component and differs among treatments. The duration of follow-up and the effect size of experimental groups correlate with the magnitude of the placebo component, underlining the importance of RCTs to determine the effectiveness of new treatments of patellar tendinopathy.

Project description:ObjectiveVitamin D (vitD) deficiency is a global childhood health problem. Food fortification is a promising strategy to curb vitD deficiency. We aimed to assess the effectiveness of utilizing vitD fortification in staple foods to improve 25hydroxyvitamin D (25(OH)D) concentration and to reduce the prevalence of vitD deficiency among healthy children.MethodsWe conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) evaluating the use of vitD fortified food products compared to no fortification among healthy children aged 1-18 years old. We searched Medline, Embase, Global Health, and Cochrane (CENTRAL) databases from database inception until May 2019. Independently, six reviewers in pairs screened titles and abstracts, assessed the full text for eligibility, and performed data extraction and quality assessment. The primary outcome is the impact of fortification on 25(OH)D concentration. The secondary outcomes included the impact of fortification on the prevalence of vitD deficiency, school performance, cognitive function, school absences, infection rate, hospital admission length, and compliance with fortified food product consumption.ResultsWe identified 2229 articles. After assessing eligibility, 20 RCTs met the inclusion criteria. The eligible RCTs assessed the fortification of milk, cereal, juice, bread, yogurt, and cheese compared with no fortification. All RCTs, except for three, had a low risk of bias. Food fortification improved 25(OH)D concentration by a mean difference (MD) of 15.51 nmol/L (95% confidence interval (CI) 6.28, 24.74; I2 = 99%), which resulted in a mean increase of 3 nmol/l for every 100 IU of vitD, when adjusted for baseline 25(OH)D concentration and country latitude. Additionally, the prevalence of vitD deficiency decreased by a risk ratio of 0.53 (95% CI 0.41, 0.69; I2 = 95%), and cognitive function improved by a MD of 1.22 intelligence quotient (IQ) points (95% CI 0.65, 1.79; I2 = 0%). The overall evidence quality was high.ConclusionVitD food fortification is an effective way to improve 25(OH)D concentration, prevent vitD deficiency, and improve IQ levels.Systematic review registrationPROSPERO CRD42017057631.

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

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

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