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MEDIA RELEASE
Wednesday 14 October 2009
Are we misunderstanding the placebo response?
Science may be rejecting potentially effective and valuable therapeutic treatments because of
confusion around the placebo effect.
New research from the Jean Hailes Foundation for Women’s Health in Melbourne raises a question
mark over how science interprets physiological or psychological health benefits ascribed to the
placebo effect – and often dismissed.
The research supports the theory that people may rely on different neuro-biological mechanisms when
they are given a pharmacological treatment as opposed to when they are given a placebo. Some
researchers have previously suggested placebo and pharmacological interventions activate mutually
exclusive pathways – with both providing benefits.
“Essentially, the trial participants would experience either placebo or pharmacological intervention
effects, but not both,” says lead researcher, Dr Diana van Die.
“So if you get a pharmacological effect, you don’t get the psychological placebo effect – the placebo
effect only operates in the absence of a pharmacological effect.
“The implications of this, if correct, are huge because this would invalidate the assumption that
intervention effects are additive to placebo effects – ie that subtracting the placebo effect from the
treatment effect leaves the active intervention effect.”
The placebo-controlled trial is the gold standard of clinical research, with the aim of researchers being
to accurately determine the specific effect of an intervention or treatment over and above the placebo
effect.
If an intervention or treatment shows no significant effects over the placebo, it is often dismissed and
disregarded.
But the new research from the Foundation concludes that some potentially valuable therapeutic
treatments may be unnecessarily dismissed because of the complex nature of the placebo effect.
The research by Dr van Die and her team was based on the findings of a previous study of 93 late peri-
menopausal or post-menopausal women who were divided into an active treatment or placebo group.
The active treatment group received two Vitex agnus-castus (chaste tree/berry) tablets and three
Hypericum perforatum (St John’s wort) tablets daily, while the placebo group received placebo tablets
that were identical in appearance.
The herbal tablets were being studied for their efficacy in alleviating menopause-related symptoms.
The study concluded that the herbal combination had a ‘significant effect’ on menopausal symptoms,
but was not superior to placebo.
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Dr van Die says this latest research on the placebo effect is particularly important for considering
treatments for conditions like depression and menopause, where studies traditionally have a high
placebo response.
“There is an average 51 per cent response in menopause studies of hot flushes. So if someone gets a 66
per cent improvement with their drug or herb it would be discounted as not valuable because it’s not
seen as being statistically superior to placebo,” says Dr van Die.
“But bearing in mind this latest research about the placebo effect, you’d have to look at the magnitude
of the effect of the treatment, independent of the placebo effect, and ask ‘is that clinically relevant?’
“If women who are having hot flushes can’t go on HRT, or don’t want to go on HRT, would they be
satisfied with a 66 per cent improvement in their symptoms – regardless of what the placebo response
is?
“In some depression studies you can get 75 per cent of the effect of the drug replicated in the placebo
arm. Someone who gets a 75 per cent reduction in their symptoms of depression may be very happy
with that.
“Depending on what the condition is and what else is available as treatment, a small improvement in
symptoms might be better than nothing. This would mean interpreting the results from placebo-
controlled studies differently by saying ‘with a placebo you can get this much effect and with the
active treatment you get 10 or 15 per cent more. Never mind the placebo effect, is this valuable?’”
In addition, the research identifies some predictors of higher placebo effect, such as anxiety and
increasing age. This information is potentially beneficial to researchers as it allows them to take these
predictors into account at the start of their research – and so reduce the potential impact of placebo
response on their study findings.
“The placebo effect is considered a nuisance in research,” says Dr van Die.
“It’s a boon in clinical practice because if people are going to get better when you give them a sugar
pill, that’s great. But in clinical trials the placebo effect is a nuisance because high placebo effect will
often mean your active treatment doesn’t out-perform the placebo and is therefore concluded to be
ineffective. It gets dismissed.
“Your treatment has to do quite a bit better than the placebo to be regarded as significant. After all, if
someone can get improvement by taking a sugar pill why would they spend more money on herbs or
drugs to only get a marginally better improvement?
“The whole assumption of the placebo effect needs to be explored further because it does significantly
impact on the conclusions drawn from studies, and it may be the case that potentially valuable
therapeutic agents are being rejected inappropriately.”
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MEDIA
To interview Dr van Die or Jean Hailes Research Director Professor Helena Teede please call Aleeza
Zohar on (03) 9562 6771 or 0425 758 729.
NEWS 
