Which placebo to cure depression? A thought-provoking network meta-analysis

When does the placebo effect have an impact on network meta-analysis results?

The placebo effect is the 'effect of the simulation of treatment that occurs due to a participant's belief or expectation that a treatment is effective'. Although the effect might be of little importance for some conditions, it can have a great role in others, mostly when the evaluated symptoms are subjective. Several characteristics that include informed consent, number of arms in a study, the occurrence of adverse events and quality of blinding may influence response to placebo and possibly bias the results of randomised controlled trials. Such a bias is inherited in systematic reviews of evidence and their quantitative components, pairwise meta-analysis (when two treatments are compared) and network meta-analysis (when more than two treatments are compared). In this paper, we aim to provide red flags as to when a placebo effect is likely to bias pairwise and network meta-analysis treatment effects. The classic paradigm has been that placebo-controlled randomised trials are focused on estimating the treatment effect. However, the magnitude of placebo effect itself may also in some instances be of interest and has also lately received attention. We use component network meta-analysis to estimate placebo effects. We apply these methods to a published network meta-analysis, examining the relative effectiveness of four psychotherapies and four control treatments for depression in 123 studies.

Perils of prolonged ovarian suppression and hypoestrogenism in the treatment of breast cancer: Is the risk of treatment worse than the risk of recurrence?

Premenopausal breast cancer is usually estrogen receptor positive, and hence, prolonged ovarian suppression by medical or surgical means to prevent recurrence has become standard of management to improve disease-free survival. Ten-year adjuvant tamoxifen therapy is associated with 3.5% fewer recurrences compared to five years. The SOFT trial demonstrated small but statistically significant incremental improvements in long-term disease-free survival by the addition of gonadotropin-releasing hormone analog treatment (triptorelin) to an aromatase inhibitor (exemestane). Profound hypoestrogenism in the premenopausal age group may not be well tolerated due to a host of bothersome side effects (primarily vasomotor symptoms, musculoskeletal complaints, genitourinary syndrome of menopause, and mood disorders). Prolonged hypoestrogenism in younger women is associated with premature development of cardiovascular disease, bone loss, cognitive decline, and all-cause mortality. This paper explores multi-system consequences of prolonged hypoestrogenism in premenopausal women derived from studies of women with and without breast cancer. Pretreatment counseling in estrogen receptor positive breast cancer should emphasize the benefit of prolonged estrogen suppression on breast cancer recurrence and established risks of lifelong hypoestrogenism on quality of life and all-cause mortality. Future genomic research may help identify the best candidates for extended ovarian suppression to avoid treating many women when only a minority benefit.

Comparative efficacy of placebos in short-term antidepressant trials for major depression: a secondary meta-analysis of placebo-controlled trials

BACKGROUND

The issue of unblinded outcome-assessors and patients has repeatedly been stressed as a flaw in allegedly double-blind antidepressant trials. Unblinding bias can for example result from a drug's marked side effects. If such unblinding bias is present for a given drug, then it might be expected that the placebos of that drug are rated significantly less effective than that of other antidepressants.

METHODS

To test this hypothesis, the present exploratory analysis conducted a Bayesian network meta-analysis (NMA) comparing the efficacy of 19 different placebos in placebo-controlled trials provided in the dataset by Cipriani et al. (Lancet 2018; 391: 1357-66). Primary outcome was efficacy (continuous) estimated on the standardized mean difference (SMD) scale and defined as the pre-post change on the Hamilton Depression scale (HAMD-17), on which information was available in N = 258 trials.

RESULTS

Comparative placebo ranking suggested mirtazapine-placebo (SMD -2.0 [- 5.0-1.0 95% CrI]) to be the most, and amitriptyline- (SMD 1.2 [- 1.6-3.9 95% CrI]) and trazodone- (SMD 2.1 [- 0.9-5.2 95% CrI]) placebos to be the least effective placebos. Other placebos suggested to be more effective than amitriptyline- and trazodone-placebos (based on 95% CrIs excluding zero) were citalopram, desvenlafaxine, duloxetine, escitalopram, fluoxetine, sertraline, and venlafaxine placebos. These NMA results were corroborated by the observation that the relative efficacy between drug and placebo was considerably larger for amitriptyline and trazodone than for instance mirtazapine, duloxetine, and venlafaxine, supported by a small and insignificant correlation between drug-efficacy and placebo-efficacy (r = - 0.202, p = 0.408).

DISCUSSION

The present exploratory NMA indicates that distinguishable side effects of older drugs may unblind outcome-assessors thus resulting in overestimation of the average drug-placebo difference and underrating bias in placebo-arms, particularly for the older antidepressant drugs amitriptyline and trazodone. If confirmed in prospective studies, these findings suggest that efficacy rankings for antidepressants are susceptible to bias and should be considered unreliable or misleading. The analysis is limited by the focus on the single-comparison placebos (76%, i.e., placebos assessed in two-arm trials), since double-comparison placebos (25%, i.e., placebos assessed in three-arm trials) are hard to interpret and therefore not included in the present interpretation. Another limitation is the problem of multiplicity, which was only approximately accounted for in the Bayesian NMA by modelling treatment effects as exchangeable.

[What place for placebo in clinical trials conducted on psychiatric patients?]

Placebo effect remains a crucial issue in current clinical trials. Most clinical trials rely on the hypothesis of equivalent placebo response rates in both placebo and specific drug arms ("additive model"). But contrary to this dominant and rarely questioned hypothesis, several aspects may influence placebo response. A few recent meta-analyses and reviews have shown evidence for several clinical and methodological factors, which are able to modulate placebo response. In psychiatry research, placebo response has been mainly explored through antidepressant trials. In early clinical trials, drug-placebo differences were initially significant and robust. However, more recent clinical trials have not yielded similar results, and rather show narrowed antidepressant-placebo differences. Several factors may be involved in this absence of comparability: intrinsic properties of new antidepressants, changes in clinical criteria and classifications, symptomatic remission rather than global remission criteria, industrial and institutional constraints. Moreover, results from antidepressant trials (laboratory conditions) remain hardly fully transposable to clinical routine (ecological conditions).

Has the rising placebo response impacted antidepressant clinical trial outcome? Data from the US Food and Drug Administration 1987-2013

More than fifteen years ago, it was noted that the failure rate of antidepressant clinical trials was high, and such negative outcomes were thought to be related to the increasing magnitude of placebo response. However, there is considerable debate regarding this phenomenon and its relationship to outcomes in more recent antidepressant clinical trials. To investigate this, we accessed the US Food and Drug Administration (FDA) reviews for sixteen antidepressants (85 trials, 115 trial arms, 23,109 patients) approved between 1987 and 2013. We calculated the magnitude of placebo and antidepressant responses, antidepressant-placebo differences, as well as the effect sizes and success rates, and compared these measures over time. Exploratory analysis investigated potential changes in trial design and conduct over time. As expected, the magnitude of placebo response has steadily grown in the past 30 years, increasing since 2000 by 6.4% (r=0.46, p<0.001). Contrary to expectations, a similar increase has occurred in the magnitude of antidepressant response (6.0%, r=0.37, p<0.001). Thus, the effect sizes (0.30 vs. 0.29, p=0.42) and the magnitude of antidepressant-placebo differences (10.5% vs. 10.3%, p=0.37) have remained statistically equivalent. Furthermore, the frequency of positive trial arms has gone up in the past 15 years (from 47.8% to 63.8%), but this difference in frequency has not reached statistical significance. Trial design features that were previously associated with a possible lower magnitude of placebo response were not implemented, and their relationship to the magnitude of placebo response could not be replicated. Of the 34 recent trials, two implemented enhanced interview techniques, but both of them were unsuccessful. The results of this study suggest that the relationship between the magnitude of placebo response and the outcome of antidepressant clinical trials is weak at best. These data further indicate that antidepressant-placebo differences are about the same for all of the sixteen antidepressants approved by the FDA in the past thirty years.

GetReal in network meta-analysis: a review of the methodology

Pairwise meta-analysis is an established statistical tool for synthesizing evidence from multiple trials, but it is informative only about the relative efficacy of two specific interventions. The usefulness of pairwise meta-analysis is thus limited in real-life medical practice, where many competing interventions may be available for a certain condition and studies informing some of the pairwise comparisons may be lacking. This commonly encountered scenario has led to the development of network meta-analysis (NMA). In the last decade, several applications, methodological developments, and empirical studies in NMA have been published, and the area is thriving as its relevance to public health is increasingly recognized. This article presents a review of the relevant literature on NMA methodology aiming to pinpoint the developments that have appeared in the field. Copyright © 2016 John Wiley & Sons, Ltd.

Effectiveness and Implications of Alternative Placebo Treatments: A Systematic Review and Network Meta-analysis of Osteoarthritis Trials

BACKGROUND

Placebo controls are essential in evaluating the effectiveness of medical treatments. Although it is unclear whether different placebo interventions for osteoarthritis vary in efficacy, systematic differences would substantially affect interpretation of the results of placebo-controlled trials.

OBJECTIVE

To evaluate the effects of alternative placebo types on pain outcomes in knee osteoarthritis.

DATA SOURCES

MEDLINE, EMBASE, Web of Science, Google Scholar, and Cochrane Database from inception through 1 June 2015 and unpublished data.

STUDY SELECTION

149 randomized trials of adults with knee osteoarthritis that reported pain outcomes and compared widely used pharmaceuticals against oral, intra-articular, topical, and oral plus topical placebos.

DATA EXTRACTION

Study data were independently double-extracted; study quality was assessed by using the Cochrane risk of bias tool.

DATA SYNTHESIS

Placebo effects that were evaluated by using a network meta-analysis with 4 separate placebo nodes (differential model) showed that intra-articular placebo (effect size, 0.29 [95% credible interval, 0.09 to 0.49]) and topical placebo (effect size, 0.20 [credible interval, 0.02 to 0.38]) had significantly greater effect sizes than did oral placebo. This differential model showed marked differences in the relative efficacies and hierarchy of the active treatments compared with a network model that considered all placebos equivalent. In the model accounting for differential effects, intra-articular and topical therapies were superior to oral treatments in reducing pain. When these differential effects were ignored, oral nonsteroidal anti-inflammatory drugs were superior.

LIMITATIONS

Few studies compared different placebos directly. The study could not decisively conclude whether disease severity and co-interventions systematically differed between trials evaluating different placebos.

CONCLUSION

All placebos are not equal, and some can trigger clinically relevant responses. Differential placebo effects can substantially alter estimates of the relative efficacies of active treatments, an important consideration for the design of clinical trials and interpretation of their results.

PRIMARY FUNDING SOURCE

Agency for Healthcare Research and Quality.

Long term sertraline effects on neural structures in depressed and nondepressed adult female nonhuman primates

BACKGROUND

Selective serotonin reuptake inhibitors (SSRIs) are widely prescribed for mood and other disorders. However, their neural effects are difficult to study due to patient compliance and drug history variability, and rarely studied in those prescribed SSRIs for non-mood disorders. Here we evaluated SSRI effects on neural volumetrics in depressed and nondepressed monkeys.

METHODS

42 socially-housed cynomolgus monkeys were randomized to treatment balanced on pretreatment depressive behavior and body weight. Monkeys were trained for oral administration of placebo or 20 mg/kg sertraline HCl daily for 18 months and depressive and anxious behavior recorded. Volumes of neural regions of interest in depression were measured in magnetic resonance images and analyzed by 2 (depressed, nondepressed)×2 (placebo, sertraline) ANOVA.

RESULTS

Sertraline reduced anxiety (p=0.04) but not depressive behavior (p=0.43). Left Brodmann's Area (BA) 32 was smaller in depressed than nondepressed monkeys (main effect of depression: p<0.05). Sertraline and depression status interacted to affect volumes of left Anterior Cingulate Cortex (ACC), left BA24, right hippocampus (HC), and right anterior HC (sertraline×depression interactions: all p's<0.05). In the Placebo group, depressed monkeys had smaller right anterior HC and left ACC than nondepressed monkeys. In nondepressed monkeys, sertraline reduced right HC volume, especially right anterior HC volume. In depressed monkeys sertraline increased left ACC volume. In nondepressed monkeys, sertraline reduced left BA24 volumes resulting in smaller BA24 volumes in nondepressed than sertraline-treated depressed monkeys.

CONCLUSIONS

These observations suggest that SSRIs may differentially affect neural structures in depressed and nondepressed individuals.

Effects of long-term sertraline treatment and depression on coronary artery atherosclerosis in premenopausal female primates

OBJECTIVES

Major depressive disorder and coronary heart disease often co-occur in the same individuals. Selective serotonin reuptake inhibitors (SSRIs) are widely prescribed for depression and other disorders, but their effects on coronary heart disease risk remain unclear. We determined the effects of an SSRI on coronary artery atherosclerosis (CAA) in an established nonhuman primate model used to clarify the association between depression and CAA.

METHODS

Forty-two adult female cynomolgus macaques consuming a Western diet were characterized during an 18-month pretreatment phase and assigned to SSRI (sertraline hydrochloride 20 mg/kg, per os, once a day) or placebo balanced on pretreatment depression, body weight (BW), and iliac artery atherosclerosis extent measured via biopsy. After 18 months, CAA extent was measured using histomorphometry.

RESULTS

Before and during treatment, depressed monkeys had lower BW, body mass index, and plasma high-density lipoprotein cholesterol, and higher heart rates during the pretreatment (p < .01) but not the treatment phase (p = .17). There were no pretreatment differences between the sertraline and placebo groups. Sertraline reduced anxious behavior but had no effect on BW, body mass index, heart rate, plasma lipids, or depression. CAA, analyzed by a 2 (depressed, nondepressed) × 2 (placebo, sertraline) × 3 (coronary arteries) analysis of covariance adjusted for pretreatment iliac atherosclerosis, was greater in depressed than in nondepressed monkeys (p < .036), and in sertraline than in placebo-treated monkeys (p = .040). The observed CAA extent in depressed monkeys treated with sertraline was 4.9 times higher than that in untreated depressed monkeys, and 6.5 times higher than that in nondepressed monkeys, on average.

CONCLUSIONS

Depressed animals developed more CAA, and long-term treatment with sertraline resulted in more extensive CAA.

Placebo eff ects in psychiatry: mediators and moderators

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

Understanding the Antidepressant Debate in the Treatment of Major Depressive Disorder

There is a long-standing polemic concerning the usefulness of antidepressants in the treatment of major depressive disorder. In this paper, we propose to highlight some aspects of this controversy by exploring the mutual influence of psychopharmacology and trial methodologies. Indeed, antidepressant efficacy, if not proved, was accepted before antidepressant randomised controlled trials (RCTs) were run. While RCTs became a gold standard to meet the requirements of the regulatory bodies, methodological tools were required to measure outcomes and to test whether antidepressants provide statistically significant benefits as compared with a placebo. All these methodological options have nonetheless introduced fuzziness in our interpretation of study results, in terms of clinical meaningfulness and in terms of transposability to a real life settings. Additionally, selective publication raises concerns about the published literature, and results in many paradoxes. Instead of providing easy answers, the application of the RCT paradigm in MDD raises numerous questions. This is probably in the nature of all scientific studies, but it can be in contradiction with clinicians' expectations, who want to be sure that the treatment will (or will not) work for their individual patients.

From Randomized Controlled Trials of Antidepressant Drugs to the Meta-Analytic Synthesis of Evidence: Methodological Aspects Lead to Discrepant Findings

During the last decade, several meta-analytic studies employing different methodological approaches have had inconsistent conclusions regarding antidepressant efficacy. Herein, we aim to comment on methodological aspects that may have contributed to disparate findings. We initially discuss methodological inconsistencies and limitations related to the conduct of individual antidepressant randomized controlled trials (RCTs), including differences in allocated samples, limitations of psychometric scales, possible explanations for the heightened placebo response rates in antidepressant RCTs across the past two decades as well as the reporting of conflicts of interest. In the second part of this article, we briefly describe the various meta-analyses techniques (e.g., simple random effects meta-analysis and network meta-analysis) and the application of these methods to synthesize evidence related to antidepressant efficacy. Recently published antidepressant metaanalyses often provide discrepant results and similar results often lead to different interpretations. Finally, we propose strategies to improve methodology considering real-world clinical scenarios.

The definition of placebo in the informed consent forms of clinical trials

Aim

Lack of knowledge concerning the nature of placebo and why it is necessary may influence the participation of patients in clinical trials. The objective of the present study is to review how placebo is described in written information for participants in clinical trials to be evaluated by a Human Research Ethics Committee.

Methods

All research protocols submitted for evaluation in a Spanish hospital during 2007–2013 were reviewed. The main characteristics of the studies using a placebo were collected. Three authors read each of them to determine how the term “placebo” was explained and if there was any comment on its efficacy and safety.

Results

Two thousand seven-hundred and forty research protocols were evaluated, of which three hundred and fifty-nine used a placebo. Pharmaceutical companies sponsored most placebo-controlled clinical trials (91.9%), and phase III studies were the commonest (59.9%). Oncology (15.0%), cardiology (14.2%), and neurology (13.1%) made the greatest contributions. A review of the informed consent forms showed that placebo was described in a similar manner in most studies: the explanation was limited to between four and eight words. Very few gave information about the risks of its use or adverse reactions from its administration. None of the studies provided details about the placebo effect. And 23 lacked any information about placebo at all.

Conclusions

Explanations about placebo in informed consent forms is often scarce, and information about the placebo effect and associated risks are absent. This situation may influence a full understanding of placebo by participants in clinical trials and might reduce their informed decision to participate.

Placebo for depression: we need to improve the quality of scientific information but also reject too simplistic approaches or ideological nihilism

The placebo response plays a major role in psychiatry, particularly in depression. A new network meta-analysis investigates whether the effects of placebo vary in studies comparing fluoxetine and venlafaxine, two widely prescribed antidepressants. Even though data from this article indicate that the effects of placebos do not differ, publication bias cannot be ruled out. The authors use their finding to criticise the paradigm of evidence-based medicine, questioning whether there is anything certain in psychiatry and, more precisely, in the field of antidepressant treatment for major depression. This study stimulates the debate about validity of scientific knowledge in medicine and highlights the importance of considering things from a different perspective. However, the authors' view should be considered with caution. As clinicians, we make decisions every day, integrating individual clinical expertise and patients' preferences and values with the best, up-to-date research data. The quality of scientific information must be improved, but we still think that valid conclusions to help clinical practice can be drawn from a critical and cautious use of the best available, if flawed, evidence.

Does reductio ad absurdum have a place in evidence-based medicine?

In a meta-analysis published in BMC Medicine, we explored whether evidence-based medicine can actually be sure that 'sucrose = sucrose' in the treatment of depression. This paper, based upon a reductio ad absurdum, addressed an epistemological question using a 'scientific' approach, and could be disconcerting as suggested by Cipriani and Geddes' commentary. However, most papers are based upon a mixture of observations and discussions about sense and meaning. Ultimately, there is nothing more than a story, told with words or numbers. Randomised controlled trials provide information about average patients that do not exist. These results ignores an entire segment of therapeutics that plays a crucial role, namely care. This information is usually set out using a 'grammar' that is ambiguous, since statistical tests of hypothesis have raised epistemological questions that are not as yet solved. Moreover, many of these stories remain untold, and unpublished. For these reasons evidence-based medicine is a vehicle for many paradoxes and controversies. Reductio ad absurdum can be useful in precisely this case, to underline how and why the medical literature can sometimes give an impression of absurdity of this sort. Even if the data analysis in our paper was rather rhetorical, we agree that it should comply with the classic standards of reporting and we provide the important extra data that Cipriani and Geddes have requested.