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Home > Conditions and treatments > Medications - Introduction to
medications > Placebo effect
Placebo effect
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Placebo effect
Summary
A placebo is any medical treatment that is inert (inactive), such as a
sugar pill. Around one third of people who take placebos (believing
them to be medication) will experience an end to their symptoms. This
is called the placebo effect.
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Placebo is Latin for 'I will please', and refers to any medical
treatment that is inert. The placebo has long been used in research
trials to objectively test the efficacy of a new health care treatment,
such as a drug. A placebo is indispensable to the conduct of many
scientifically-based clinical trials. Ethical considerations require
that participants in clinical trials be told that they may be given a
'dummy' treatment.
Usually, one group of people takes the drug while another group (the
control group) takes the placebo. The placebo may be a sugar pill. None
of the participants know whether they are taking the active or inactive
substance. Sometimes, not even the researchers know (double blind
test).
Comparing the results from both groups should indicate the effects of
the drug. However, people sometimes get better when they are taking a
placebo. This phenomenon is known as 'the placebo effect'. Estimates
vary, but around one third of people taking placebos for complaints
(including pain, headache and seasickness) will experience relief from
symptoms. There are various theories that attempt to explain this
phenomenon but the underlying mechanisms remain mysterious.
Types of placebos
A placebo doesn't have to be a pill. It can be any inert or 'dummy'
treatment, such as special diets, exercise, physical therapy or even
surgery. The placebo effect is triggered by the person's belief in the
treatment and their expectation of feeling better, rather than the
specific form the placebo takes.
The misconception of 'imaginary' disorders
If a person's symptoms are relieved by taking an inert substance or
undergoing a dummy procedure, it seems logical to assume that their
illness must have been imaginary. This is not the case. Medical
research has shown that psychological states play an important role in
the development of disease. For example, stress is known to increase
blood pressure, and chronic hypertension is a risk factor for heart
disease. Just as the mind can contribute to a physical disorder, it can
also contribute to its cure.
Influencing factors
Some of the factors that influence the placebo effect include:
* The characteristics of the placebo - if the pill looks genuine, the
person taking it is more likely to believe that it contains
medicine. Research shows that larger sized pills suggest a stronger
dose than smaller pills, and taking two pills appears more potent
than swallowing just one. Generally, injections have a more
powerful effect than pills.
* The person's attitude - if the person expects the treatment to
work, the chances of a placebo effect are higher. Some studies show
that the placebo effect may still take place even if the person is
sceptical of success. The power of suggestion may be at work here.
* Doctor-patient relationship - if the person trusts their health
care practitioner, they are more likely to believe that the placebo
will work.
How placebos work
The exact physiological mechanisms remain mysterious. Some of the
theories that attempt to explain the placebo effect include:
* Self-limiting disorders - many conditions, such as the common cold,
are self-limiting. They will resolve by themselves anyway, with or
without placebos or drugs, and the end of symptoms is merely
coincidence.
* Remission - the symptoms of some disorders, such as multiple
sclerosis and lupus, may wax and wane. A remission during a course
of placebos may be coincidence, and not due to the placebos at all.
* A change in behaviour - the placebo may increase a person's
motivation to take better care of themselves. Improved diet,
regular exercise or rest may be responsible for the easing of their
symptoms.
* Altered perception - the person's interpretation of their symptoms
may change with the expectation of feeling better. For example, a
sharp pain may be reinterpreted as an uncomfortable tingling.
* Reduced anxiety - taking the placebo and expecting to feel better
may soothe the autonomic nervous system and reduce the levels of
stress chemicals, such as adrenaline.
* Brain chemicals - placebos may trigger the release of the body's
own natural painkillers, the brain chemicals (neurotransmitters)
known as endorphins.
* Altered brain state - research indicates that the brain responds to
an imagined scene in much the same way as it responds to an actual
visualised scene. A placebo may help the brain to remember a time
before the onset of symptoms, and then bring about physiological
change. This theory is called 'remembered wellness'.
The argument against placebos
Placebos have the power to cause unwanted side effects. Nausea,
drowsiness and allergic reactions, such as skin rashes, have been
reported as placebo effects. Critics of placebos maintain that
deception is wrong, regardless of whether the deceived patient
experiences an end to their symptoms. The longterm prescription of
placebos by an unscrupulous health care practitioner may also convince
an otherwise healthy person that they are suffering from an illness or
infection that requires ongoing treatment. The mind-set of believing
oneself to be ill may contribute to the onset of genuine symptoms. A
good doctor-patient relationship with good communication is usually
preferable to the use of a placebo.
The placebo effect is doubted by some
Some researchers doubt the placebo effect even exists. For example,
medical philosophers at the University of Copenhagen recently analysed
trials that involved placebos and declared that placebos offered about
the same degree of symptom relief as no medical treatment. Critics
point out that the methodology used by the medical philosophers was
flawed, and that the placebo effect has been well documented for many
years.
Where to get help
* Your doctor
Things to remember
* A placebo is any medical treatment that is inert, such as a sugar
pill.
* Around one third of people who take placebos (believing them to be
medication) will experience an end to their symptoms.
* Belief in a treatment may be enough to change the course of a
person's physical illness.
You might also be interested in:
+ Clinical trials.
Want to know more?
Go to More information for support groups, related links and
references.
This page has been produced in consultation with and approved by:
Monash University - Centre for Developmental Psychiatry and
Psychology
(Logo links to further information)
Monash University - Centre for Developmental Psychiatry and
Psychology
Fact sheet currently being reviewed.
Last reviewed: October 2011
Content on this website is provided for education and information
purposes only. Information about a therapy, service, product or
treatment does not imply endorsement and is not intended to replace
advice from your doctor or other registered health professional.
Content has been prepared for Victorian residents and wider
Australian audiences, and was accurate at the time of publication.
Readers should note that, over time, currency and completeness of
the information may change. All users are urged to always seek
advice from a registered health care professional for diagnosis and
answers to their medical questions.
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Placebo effect - Better Health
Channel
A placebo is any medical treatment that is inert (inactive), such
as a sugar pill. Around one third of people who take placebos
(believing them to be medication) will experience an end to their
symptoms. This is called the placebo effect.
Content on this website is provided for education and information
purposes only. Information about a therapy, service, product or
treatment does not imply endorsement and is not intended to replace
advice from your qualified health professional. Content has been
prepared for Victorian residence and wider Australian audiences,
and was accurate at the time of publication. Readers should note
that over time currency and completeness of the information may
change. All users are urged to always seek advice from a qualified
health care professional for diagnosis and answers to their medical
questions.
For the latest updates and more information, visit
www.betterhealth.vic.gov.au
Copyight (c) 1999/2014 State of Victoria. Reproduced from the
Better Health Channel (www.betterhealth.vic.gov.au) at no cost with
permission of the Victorian Minister for Health. Unauthorised
reproduction and other uses comprised in the copyright are
prohibited without permission.
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Last updated 10/31/2013