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Healthy Skepticism Library item: 15932

Warning: This library includes all items relevant to health product marketing that we are aware of regardless of quality. Often we do not agree with all or part of the contents.

 

Publication type: Journal Article

Van Die MD, Bone KM, Burger HG, Teede HJ.
Are we drawing the right conclusions from randomised placebo-controlled trials? A post-hoc analysis of data from a randomised controlled trial
BMC Medical Research Methodology 2009 2009 Jun 23; 9:(41):
http://www.biomedcentral.com/1471-2288/9/41/abstract


Abstract:

Background
Assumptions underlying placebo controlled trials include that the placebo effect impacts on all study arms equally, and that treatment effects are additional to the placebo effect. However, these assumptions have recently been challenged, and different mechanisms may potentially be operating in the placebo and treatment arms. The objective of the current study was to explore the nature of placebo versus pharmacological effects by comparing predictors of the placebo response with predictors of the treatment response in a randomised, placebo-controlled trial of a phytotherapeutic combination for the treatment of menopausal symptoms. A substantial placebo response was observed but no significant difference in efficacy between the two arms.

Methods
A post hoc analysis was conducted on data from 93 participants who completed this previously published study. Variables at baseline were investigated as potential predictors of the response on any of the endpoints of flushing, overall menopausal symptoms and depression. Focused tests were conducted using hierarchical linear regression analyses. Based on these findings, analyses were conducted for both groups separately. These findings are discussed in relation to existing literature on placebo effects.

Results
Distinct differences in predictors were observed between the placebo and active groups. A significant difference was found for study entry anxiety, and Greene Climacteric Scale (GCS) scores, on all three endpoints. Attitude to menopause was found to differ significantly between the two groups for GCS scores. Examination of the individual arms found anxiety at study entry to predict placebo response on all three outcome measures individually. In contrast, low anxiety was significantly associated with improvement in the active treatment group. None of the variables found to predict the placebo response was relevant to the treatment arm.

Conclusions
This study was a post hoc analysis of predictors of the placebo versus treatment response. Whilst this study does not explore neurobiological mechanisms, these observations are consistent with the hypotheses that ‘drug’ effects and placebo effects are not necessarily additive, and that mutually exclusive mechanisms may be operating in the two arms. The need for more research in the area of mechanisms and mediators of placebo versus active responses is supported. Current Controlled Trials ISRCTN98972974

 

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...to influence multinational corporations effectively, the efforts of governments will have to be complemented by others, notably the many voluntary organisations that have shown they can effectively represent society’s public-health interests…
A small group known as Healthy Skepticism; formerly the Medical Lobby for Appropriate Marketing) has consistently and insistently drawn the attention of producers to promotional malpractice, calling for (and often securing) correction. These organisations [Healthy Skepticism, Médecins Sans Frontières and Health Action International] are small, but they are capable; they bear malice towards no one, and they are inscrutably honest. If industry is indeed persuaded to face up to its social responsibilities in the coming years it may well be because of these associations and others like them.
- Dukes MN. Accountability of the pharmaceutical industry. Lancet. 2002 Nov 23; 360(9346)1682-4.