The placebo effect

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Forty patients with asthma, emphysema, or restrictive lung disease were given an inhaler that contained a nebulised saline placebo, but they were told that it contained allergens that would restrict their airways. It was a study conducted in the departments of psychiatry and medicine at the State University of New York.

Before long, 19 of the forty patients reacted with considerable constriction of their airways. Twelve of them, in fact, had an actual asthma attack.

They were then given a different inhaler and told it would relieve their symptoms. It did precisely that, yet it was also a saline placebo inhaler.

So the same placebo was able to either create or eliminate bronchospasm depending on what the patients believed it would do.

Similarly, the same placebo could induce or cancel pain, bring about or reduce nausea, or even act as a stimulant or a sedative, depending on what a person believed it was for.

Could an apple reduce pain? Chemically, perhaps not. But if someone believed it would then there’s a fair chance that they’d get at least some pain reduction.

How can this be so?

The placebo effect is the effect of belief or expectation on the brain or body. A placebo can be anything. It can be a tablet, injection, a food, an object, a device, a person, even a room. It can be facilitated by reassuring words: “This pill will do the trick. Don’t worry.” It can even be the context that something is given in. 

A location that has a warm feeling and was adorned with complex named drugs or potions and where sat a doctor with a kind, reassuring smile, would help more people than a cold room with blank walls and a doctor with their back to the patient as they typed on a computer.

But it would be wrong to conclude that it’s all just in the mind and leave it at that, as if a reduction in pain or other symptoms was purely imaginary. Research shows that belief causes biochemical changes in the brain and body. An apple would reduce pain for someone if they believed it would because their belief would produce the brain’s own painkillers. They’re called endogenous opioids.

It’s the endogenous opioids that reduce the pain, not the apple, and it’s the belief that produces the endogenous opioids. That’s why it doesn’t matter all that much whether a person believes an apple, a pill, a complex looking piece of equipment, a sound, a smell, a location, or a person will reduce their pain. Here, objects and people are merely things we attach our beliefs to.

This doesn’t, of course, mean that everything is just placebo. The vast majority of medicines have a very real effect. As a former organic chemist, I can say that with some confidence. I have spent countless hours constructing molecules and then demonstrating what happens when those molecules interact with other substances. 

In a basic sense, most schoolchildren will have observed an acid interacting with an alkali in a science lab to produce salt and water. Salt has a real taste that’s not all in the mind, although a belief could alter the intensity of it – making it appear more salty or less salty. Similarly, the interaction of ethanol (alcohol) with acetic acid (vinegar) produces a substance (known as an ester) whose smell we recognise as pear drops.

Taken a little further, interactions between several substances in a sequential manner, like adding Lego blocks together one-by-one, can produce medicines that reduce blood pressure, dissolve tumours, and do many more things. This is the field of science that I did my PhD in.

Generally speaking, it’s neither all about the drug or all placebo, but a bit of both. Sometimes it’s more of one and less of the other, and sometimes it’s more of the other and less of the one. But regardless, the context that something is offered in and the person’s beliefs about the thing have real effects.

The image below shows typical effects of no treatment, placebos, and treatment, which also contains a placebo effect.

(c) Dr David R Hamilton

Many conditions have a natural course, where the body will eventually heal by itself, usually when the immune system gets a hold on things. This is what the first column shows. A few decades ago, we used to believe that the placebo effect was just the natural course of things, but we now know that’s not the case. 

The second column shows that there is a real effect of belief. Hidden within it is the natural course of a condition, but the placebo effect itself adds something significant.

And the third column shows the effect of the treatment given, and within this effect is also the impact of the placebo and the natural course of things. We usually attribute getting better all to the drug, but the other effects always play a role. The size of the role varies from one condition to the next.

So most medicines have a built in placebo effect because it’s impossible to remove the effects of the person’s belief about what they’re taking. A body of researchers now believe that we should look to use this placebo effect in clinical practice, not try to eliminate it, as it will almost always be to the patients’ benefit.

Giving a person a positive perception of a treatment or outcome can really matter.


Any way of creating or altering a perception can cause a placebo effect. In a study at Keele University in the UK, 835 women with recurring headaches were given one of four types of tablet. 

One group received a well-known branded aspirin tablet while a second group received the same aspirin but it came in cheaper packaging and was labelled ‘analgesic’, typical of a mass market generic brand. A third group received a placebo, but it was made to look like the branded aspirin, and a fourth group received a placebo that was labelled ‘analgesic’.

It turned out that the perception of the branding made quite a difference. The branded aspirin worked better than the generic aspirin, but the branded placebo also worked better than then ‘generic’ placebo, even though they were both placebos. And the branded placebo was almost as good as the generic aspirin.

Branding mattered because of what it meant. A well-known brand confers the idea of quality, and this perception generated some endogenous opioids that gave the branded aspirin a little boost over the generic one.

Perception of the type of treatment matters too. In a US study of migraine treatments, placebo injections were found to be 50 percent better than placebo tablets, yet a European study found that placebo tablets were 10 percent better than placebo injections. There was no flaw in how the studies were carried out. It mostly just comes down to language and culture. In the UK, we speak of ‘popping pills’, but in the US, people place more faith in ‘getting a shot’. The studies show that it comes down to what we have most faith in.

And perception of a doctor or physician makes a difference. The same doctor could treat two groups of patients but dress and communicate differently. For one group, he could make himself look a little older, dress smartly, wear glasses, and show care for the patient. For the other group, he could make himself look younger, dress a little dishevelled, and behave in a disinterested way. The clinical outcome in the first group would typically be better. Why? Because of the patients’ perception of the doctor.

Remember to take all your placebos

We’ve all heard doctors remind us that we must take the full course of our treatments. It turns out that we also need to take all our placebos. Data from the Coronary Drug project in the US, that involved the cholesterol lowering drug, clofibrate, showed that the five-year survival rate for patients who took the full course of their placebos was 85 per cent, but it was 72 percent for those who didn’t stick to the course.

And studies show that four placebos work better than two placebos. For example, over 79 clinical trials of anti-ulcer drugs, the ulcer healed in 44 percent of patients who took four placebos a day, but only in 36 percent of people who took two placebos a day.

So the placebo effect is not all in the mind. It is, in a sense, but what’s in the mind then causes changes in the brain and body that depend upon what is in the mind.

For me, the placebo effect is a reminder that the mind can exert an important effect on the body. From my experience, there’s lots of ways to use our minds to positively affect our health, but I’d like to finish this piece by suggesting one of the simplest and most effective ones. It’s simply to think kindly of people.

That’s all.

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  1. Lisa Burnage on January 21, 2022 at 4:34 pm

    Thank you for the research David! This is fascinating. And you’re right, we really do need to harness the power of belief. I was told “asthma is a lifelong condition”. I didn’t believe it was. It took me several years to convince my GP practice that I hadn’t had symptoms for ages. Various factors were at play, but more positivity is needed. Times are a-changing

  2. Carol Stout on January 21, 2022 at 4:52 pm

    Many blessings, David
    I heard you speak In Liverpool years ago ( Bluecoats ?)
    I really want to be able to teach this in high schools

    Love and Gratitude
    Carol Stout

  3. Gini Diane Collinson on January 21, 2022 at 5:12 pm

    Dr. Hamilton, this is mind-bending, as usual. I devoured every word. Giving us the whole back story meant it made perfect sense, even those non-scientists among us. Love the way you dropped that last piece of esoteric Wisdom in the next-to-the-last sentence!!

  4. Diane in SC on January 21, 2022 at 6:36 pm

    Great article. I bought your book “Why Woo-Woo Works” – thoroughly enjoyed it.
    Bought 6 more copies to give to our son and other friends. Thank you for the Daily
    Uplifting Prompts………they’re great. I’m spreading the word from S Carolina, USA. I was born Brit’ 85 years ago, have lived all over the world and loved every minute of it. When I think of kindness I think of you! Much love to you David.

    • David Hamilton on January 27, 2022 at 1:03 pm

      Thanks so much and for also getting copies of my book for people. That’s so kind of you. And thanks for your kind sentiment to me too. 🙂

  5. Jill Stevens on January 21, 2022 at 8:10 pm

    Thank you for your newsletter and for including the term Endogenous opioids. I have just reread Dr Lipton’s Biology of Belief.

  6. Vania on January 21, 2022 at 9:27 pm

    Thank you very much, David! As always, very interesting and informative. Your book is amazing! I’m following all your posts. All the best!

  7. Jayne Franz on January 21, 2022 at 10:21 pm

    A very interesting read yet again David! I think the potential of the mind is quite literally incredible. I met you a few Years ago at all Angels Day and then again when you gave a talk in Bradford. I still use many of your visualisation techniques to great effect! Keep up your work on this.
    Jayne Franz

  8. Jackie Dorrian on January 22, 2022 at 12:02 pm

    What a fascinating article thank you so much for sharing your knowledge and research. I am always curious around the body mind connection and how we believe in this or that. If we are kind to each other, don’t gossip and are generous our health will improve I am positive.
    Science is a wonderful practice such a vast array of incredible information. The Human Body is a fabulous piece of engineering and we can heal ourselves with kindness, positivity and treatments of which ever combination.

    I am always grateful to you for all the work you have done over the years and how you shine your light and impart your wisdom to others.

    Thank you so much.
    I met you many years ago now in Swansea

    • David Hamilton on January 27, 2022 at 1:01 pm

      I like your philosophy, Jackie: If we are kind to each other, don’t gossip and are generous, our health will improve. Kindness in action and spirit does indeed positively impact mental and physical health. And thanks so much for your kind words. 🙂

  9. Cathy near Banknock on January 23, 2022 at 10:39 am

    Hi David
    I agree with your research as a positive belief, someone you trust( ie. my mum who told me to ignore my warts when I was in primary school and they would go away, and they did much to my surprise, plus listening to our bodies all work for me. In fact pain , feeling off actually makes me angry but when I’m weak with anything like a flu I am meek and do as my body feels. I met you a few years ago in Falkirk and after your talk I surprised myself when I thanked you with a hug and you surprised me too with your reaction of humble gratitude. Never change who you are David you are a whole person doing exactly what the human race needs. Thankyou x

    • David Hamilton on January 27, 2022 at 12:59 pm

      That’s so good that you’ve had a positive experience of a placebo effect. And thanks so much for your kind words. 🙂

  10. Jacqui Sayer-Noble on January 31, 2022 at 10:25 pm

    Hello Dr Hamilton,
    I have followed your work and currently reading Why Woo Works which is an excellent book.
    Thank you for your blog on the Placebo effect is very interesting and something that is fascinating.
    I am a therapist and work mainly with a Psychotherapy called BWRT Brain Working Recursive Therapy although I am also a Hypnotherapist and Counsellor.
    I know how working with the mind can help heal the body and clearing negative trauma and emotions can have a profound effect too.
    It’s equally apparent how quickly and well therapy works when the client trusts and believes in you.
    I believe that it is the clients intent and belief that helps any therapy as in the Placebo effect.
    I look forward to reading more of your inspiring work.
    Thank you so much.

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