Placebos appear to work even when individuals know they’re placebos

Placebos are essentially inactive agents that are typically usually used in trials used to determine if a drug has genuine benefits or not. In most so-called ‘randomised, controlled trials’ individuals are assigned to take the medication or treatment being tested, while the rest get a placebo. If it turns out that the group receiving the active treatment experience benefits that are statistically significantly greater than those experienced by the placebo-taking group, then this would be evidence that the drug was more effective than placebo.

The reason for testing drugs and other treatments in this way is because of the placebo response – the improvement individuals may experience which can be related to all sorts of things including the way a practitioner talks to them, how well heard and honoured they feel, how much time they have with a practitioner, and expectations regarding their condition, its treatment and prognosis (likely outcome).

Usually, randomised controlled trials are ‘double-blind’ in nature, which means neither the researchers nor the study participants know whether an individual patient is getting the active treatment or placebo. In other words, individuals taking a placebo will usually not know that, and will believe that they have (usually) a 50:50 chance of being on the active treatment. In randomised controlled trials, an individual’s belief that they might be on the active treatment might contribute considerably to the placebo response. In theory, if an individual knew they were on placebo only, we wouldn’t expect much of a placebo response.

This concept was tested in a study which was published recently in the on-line journal PLoS ONE. In this study, individuals with irritable bowel syndrome were treated with a placebo, and told that’s exactly what they were taking. The bottle holding the placebos they were given even had the word ‘placebo’ written on them. Another group of patients with IBS were given no treatment for comparison.

After 3 weeks, 39 per cent of the group receiving nothing reported an improvement in their symptoms. In the placebo group, this figure was 59 per cent. This difference was statistically significant. The authors describe the effect as “clinically meaningful”.

Almost 3 years ago one of my blogs looked at the ethics of prescribing placebos in practice. Apparently, about half of doctors in the US do this, but are generally not transparent about it. Another approach, as I mentioned in that blog post, would be for doctors to prescribe a placebo, but also explain to their patients exactly what they’re doing. I suggested that this might jeopardise the value of the placebo.

However, this latest research suggests that perhaps I needn’t worry: it appears that individuals can get genuine benefit from a placebo, even when they know that what it is.


1. Kaptchuk TJ, et al. Placebos without Deception: A Randomized Controlled Trial in Irritable Bowel Syndrome. PLoS ONE 5(12): e15591.

5 Responses to Placebos appear to work even when individuals know they’re placebos

  1. Nigel Kinbrum 24 December 2010 at 12:50 am #

    So the adverts were right. “Nothing acts faster than Anadin.”

  2. Soul 25 December 2010 at 12:59 am #

    That is odd.

    Having IBS-D myself, I’ve noticed the placebo effect myself. When given a medication, you want it to work. Considering also that IBS, mine anyway, has its good and bad days, it is easy to correlate a good period with the illness being caused by the medication. As I would tell myself though, time would tell the truth. End the end for me none of the medications did much good sadly.

    Right now I work on diet to correct my problem. Diet has worked in the past, even gone the distance with time. Figuring a problem food out is maddening though.

  3. Rip 27 December 2010 at 2:10 pm #

    Could this phenomenon be because it’s the common viewpoint that placebos have the same beneficial effects as the medicines?

    The power of the mind to heal the body is acting when the patient believes that the placebo is the actual medicine – but could it be working as the patient thinks, “It’s just a placebo – but people who take placebos get better anyway.”?

  4. Vanessa 27 June 2012 at 12:40 am #

    I’m a student of Homeopathic medicine in my clinical practice year. I know most people ‘out there’ (and many doctors) think that our remedies are just placebos and perhaps some of them do work in that way (as do many prescribed conventional drugs, as it happens). A number of my patients have had IBS although that wasn’t their primary reason for deciding to come to me and often they just mentioned it at the end of the consultation as ‘something I’ve had for years’, but not thinking I would be interested. Many people noticed that they were worse for bread and farinaceous foods in general, and therefore tried to minimise eating those foodstuffs. I explained that I would take all their symptoms into account when arriving at my prescription even if they seemed unrelated to their presenting condition (eg migraines, plantar fasciitis, menopausal hot flushes, fibromyalgia, eczema). All of these patients have found that their IBS symptoms (as well as the aforementioned other symptoms) have ceased and that they are now able to eat the very things that they had problems with. I don’t know how homeopathy works – but, placebo or not, it doesn’t have side effects, appears to have a long-term beneficial effect (which I believe ‘placebo’ doesn’t) and benefits patients who had otherwise found now help via the conventional routes. One was even about to be tested for coeliac disease – and is very relieved that she can go back to eating everything.

    Incidentally, I discovered the benefits of homeopathy when my children were small and I didn’t want to use steroid cream for my son’s eczema, found it invaluable for their childhood ailments (and for the cat’s cystitis and, more recently, my sister’s dog’s arthritis!) and after 20 years finally managed to train as a practitioner. It’s a shame that there’s so much negative press about it because it’s cheap (perhaps pharmaceutical companies are worried?) and appears to help the body to heal itself rather than just suppress symptoms like conventional drugs do (along with their side effects and those problems) and is useful for all age groups. I am not in it to make money out of people – I think it should be available on the NHS (as it was when my son had eczema) and, if I could afford to, I would treat people for free! I have another job in a hospital paediatric department and find it so depressing that the numbers of sick children seem to be increasing all the time, and the paediatricians’ only solutions appear to be even more suppressive drugs.


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