Irritable bowel syndrome (IBS) affects 10-15% of people around the world. It is a chronic gastrointestinal disorder with symptoms including abdominal pain, discomfort, diarrhoea and constipation. Most medications are used to treat these symptoms independently of each other and few treatments relieve the symptoms of IBS as a whole (Drossman et al. 2010). Studies have demonstrated that there is a substantial, clinically significant placebo effect for IBS. This then led Harvard researchers to investigate if using placebo for IBS could be both ethical and effective.

The Harvard IBS placebo study

Technically, there have been several IBS placebo studies at Harvard, here are the two most important:

  1. In 2008, Kaptchuk’s group assessed the effects of an acupuncture placebo and the patient-practitioner relationship on the symptoms of IBS. This paved the way for the groundbreaking open-label placebo study in 2010.
  2. After discovering a substantial placebo effect in IBS, in 2010, Kaptchuk’s group looked at the possibility of using placebos honestly (open-label) to treat IBS. This study is the one everyone things of as ‘The Harvard IBS placebo study’.

Why study the IBS placebo effect?

IBS is a functional disorder affecting the gastrointestinal tract. This means that IBS is a medical condition in which the normal function of the gastrointestinal tract is impaired, but that this is largely undetectable under examination, dissection or microscopy. However, IBS is not ‘all in your head’, but rather, it is a condition with real symptoms, but those symptoms that are difficult to physically measure or detect.

It is thought that the brain may influence symptoms of functional disorders, such as IBS. The placebo effect is most effective for conditions that are mediated by the brain – neurologically or psychologically – making IBS a promising condition to investigate.

Kaptchuk’s 2008 study, demonstrated that factors which contribute to the placebo effect could have a clinically significant effect on IBS. Participants reported an improvement in symptoms up to 62% in relation to the placebo effect.

Open-label placebo and IBS

Despite the positive results from the 2008 study, the primary obstacle to using the placebo effect clinically has been the issue of informed consent. However, Kaptchuk realised that everyone had just assumed the placebo effect required deception, but in fact, no one had ever put that to the test.

In Kaptchuk’s open-label placebo trial, IBS patients were given placebos honestly and openly. They were told that they would receive a placebo, but they were also told that it could be effective. The study had two groups:

  1. No-treatment group – patients in this group did not receive a placebo, but they did experience a positive interaction with a doctor.
  2. Placebo group – patients received a positive interaction with a doctor and open-label placebos (placebos they knew were placebos).

The placebo group showed a significantly better improvement of symptoms than the no-treatment group. This improvement was found under these three categories:

  • The overall improvement of IBS symptoms as a whole. This was measured using the IBS Global Improvement Scale.
  • Adequate relief from symptoms
  • Reduction in the severity of symptoms

The improvement in quality of life, was also measured, but it was not quite as clear-cut as the other factors, yet it did show a trend, towards the placebo-group.

The no-treatment group did experience an average symptom improvement of approximately 30%, but the placebo group exceeded this with an average improvement of approximately 60%!

This demonstrated that placebos could be prescribed openly and honestly for the treatment of IBS.

How can we use the placebo effect in IBS treatment?

Now an ethical placebo treatment has been established, we need to identify a protocol for using the placebo in clinical practice. Kaptchuk is exploring whether honest placebos are more or less effective than deceptive ones and which genetic, psychological and disease factors can affect placebo response in IBS. Before more studies have been done, placebos will not be ready for clinical practice.

In 2018, Kaptchuk was one of 29 experts attending the Society for Interdisciplinary Placebo Studies conference, who has contributed to the development of a set of clinical guidelines for using the placebo effect. Unfortunately, these guidelines do not specifically outline how to use placebo for IBS, but they demonstrate some of the factors that could be involved. The guidelines are as follows:

  1. Placebo effects should be considered as a part of regular treatment.
  2. Patients should be informed about placebo and nocebo (negative placebo effects), so that treatment effects would be maximised and negative side effects would be minimised.
  3. Trust, warmth and empathy are important in the doctor-patient relationship and should be employed to maximise positive effects and minimise nocebo effects.
  4. Health-care providers should be trained to communicate with patients in a way that maximises placebo effects and minimises nocebo effects.
  5. Open-label placebos should be used over deceptively-prescribed placebos. They should only be used where there is evidence for the effectiveness of placebos and where placebos are legal.
  6. Risks, such as prescribing invasive treatments, should not be taken to maximise placebo effects.
  7. Deception should not be considered necessary to induce placebo effects.

Whilst these guidelines do not refer to IBS directly, they provide a useful structure by which to integrate placebos into clinical practice. With this in mind, we have tentatively devised some suggested criteria tailored for IBS.

  1. Placebos should only be prescribed for IBS where it is legal to do so.
  2. The use of placebo should not increase risk to patients.
  3. The clinical interaction should be designed to maximise placebo effect and minimise nocebo effects, regardless of whether a placebo or a conventional treatment is being advised.
  4. Use placebo for IBS openly, honestly and without deception.
  5. The evidence behind the placebo effect in IBS should be explained to the patient to allow them to make an informed decision and to maximise placebo effects.


  • Do you suffer from IBS? – How do you feel about these findings? Please comment and let us know your thoughts
  • Are you a clinician working with IBS patients? – How could you envision using the placebo effect for IBS in clinical practice?

Further Reading

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