The placebo effect

The placebo effect

When a person uses any type of health treatment and sees an improvement in their symptoms, they may be experiencing the placebo effect. That’s why it’s important to be aware of the placebo effect when judging the effectiveness of a treatment, or when using one ourselves.

The placebo effect is about the power of the mind to influence the body.

It can occur when a person uses any kind of health treatment – either conventional or complementary and alternative.

It can affect all of us, whether we know about the placebo effect or not.

It’s important to be aware of the placebo effect when choosing complementary and alternative medicines (CAMs). That is because if we choose a complementary or alternative treatment that does not work – and only causes a placebo effect – we may miss out on more effective treatments.

What is the placebo effect?

For hundreds of years, doctors have known that when a patient with a health condition expects their symptoms to improve, they often do improve.

Today, we know that patients who are given empty injections or pills that they believe contain medicine can experience an improvement in a wide range of health conditions. This kind of fake or empty medicine is often called a placebo, and the improvement that results is called the placebo effect.

The placebo effect is an example of how our expectations and beliefs can cause real change in our physical bodies. It’s a phenomenon that we don’t completely understand. But we can see it working in all kinds of ways, and all kinds of circumstances.

The placebo effect at work

Take one well-known example based on a physical feeling we are all familiar with: pain.

In 1996, scientists assembled a group of students and told them that they were going to take part in a study of a new painkiller, called "trivaricaine". Trivaricaine was a brown lotion to be painted on the skin, and smelled like a medicine. But the students were not told that, in fact, trivaricaine contained only water, iodine, and thyme oil – none of which are painkilling medicines. It was a fake – or placebo – painkiller. Read an abstract of the study: Mechanisms of Placebo Pain Reduction.

With each student, the trivaricaine was painted on one index finger, and the other left untreated. In turn, each index finger was squeezed in a vice. The students reported significantly less pain in the treated finger, even though trivaricaine was a fake.

In this example, expectation and belief produced real results. The students expected the "medicine" to kill pain: and, sure enough, they experienced less pain. This is the placebo effect.

Placebo medicine has even been shown to cause stomach ulcers to heal faster than they otherwise would.

These amazing results show that the placebo effect is real, and powerful. They mean that fake or placebo treatments can cause real improvements in health conditions: improvements we can see with our own eyes.

Experiencing the placebo effect is not the same as being "tricked", or being foolish. The effect can happen to everyone, however intelligent, and whether they know about the placebo effect or not.

CAM and the placebo effect

Evidence about a treatment is gathered by conducting fair tests. In these tests, scientists find out whether a treatment causes an improvement beyond the improvement caused by the placebo effect alone.

Evidence plays an important role in mainstream medicine. This means that when you use many conventional medicines, you can be sure there is evidence they work.

When patients experience improvement after using a healthcare treatment that has not been proven to work, they may only be experiencing the placebo effect.

Of course, improvement in a health condition due to the placebo effect is still improvement, and that is always welcome.

But it is important to remember that for many health conditions, there are treatments that work better than placebo treatments. If you choose a treatment that provides only a placebo effect, you will miss out on the benefit that a better treatment would provide.

Check the evidence

The only way to know whether a health treatment works better than a placebo treatment is by checking the evidence.

You can learn more about evidence, how it is gathered, and why it is important in CAM: what is evidence?.

You can read about the evidence for many of the best-known CAMs in the Health A-Z pages.

Page last reviewed: 06/02/2014

Next review due: 06/02/2016


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The 2 comments posted are personal views. Any information they give has not been checked and may not be accurate.

cybersaint said on 05 March 2015

Why do they spend so much time investigating this nonsense ?
I got another letter from Nottingham Uni saying "Here's a test kit to see if you've got bowel cancer". Does he know I've got prostrate cancer? And that's not what's wrong with me.

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rationallawful said on 04 February 2013

You rightly say 'of course, improvement in a health condition due to the placebo effect is still improvement, and that is always welcome'; however sadly certain scientists who should know better wrongly equate 'placebo' with 'invalid' and 'contrary to evidence based medicine' and then go on to bad-mouth complementary therapies including homeopathy which they say should be banned. The greatest strength of the NHS is that it is COMPREHENSIVE - see the 2012 Health and Social Care Act (Section 1.1): 'The Secretary of State must continue the promotion in England of a comprehensive health service designed to secure improvement— .(a) in the physical and mental health of the people of England, and (b) in the prevention, diagnosis and treatment of physical and mental illness’.

The time has come to find a better word than 'Placebo' which generates more heat than light. It wraps up a lot of heterogeneous concepts into a single word which is then meaningless in a scientific sense. This point has been taken up in the July 2012 in-depth (294 page) doctoral dissertation 'Evidence-based medicine, "placebos" and the homeopathy controversy' by Dr Andrew James Turner of the University of Nottingham at

which shows (page 185) that lumping a disparate range of elements together only adds to the confusion; if one wishes to say something informative about medical treatments, ‘placebo’ and ‘placebo effect’ are not terms which are analytically useful. Better to talk about 'components of treatment' one or more of which can contribute towards the effectiveness of a therapy.

A growing body of published research in good quality peer-reviewed journals shows that homeopathy has a positive effect. Healthcare is about adding years to life and life to years and homeopathy when practised (as it is)and integrated by qualified medical practitioners time and time again demonstrates that it is economic al, safe, and effective.

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Media last reviewed: 08/07/2015

Next review due: 08/07/2017