The Nocebo Effect

Ask the DOC

Most people are probably familiar with the placebo effect but may not be aware of its less popular opposite cousin, the nocebo effect. Recent research indicates that the mysterious nocebo effect may be more common than people, including medical professionals, think. The placebo effect occurs when someone, often a volunteer in a clinical trial, is receiving medication or having a procedure where both the medication and procedure is inert, yet they experience positive effects. The nocebo effect occurs when the patient has negative reactions attributable to the medication despite receiving placebo.

Most medical research today is done in the form of randomized clinical trials which are double blinded. That means that volunteers are placed in either the treatment group, which receives the medication or procedure being studied, or the control group which receives a placebo. They are placed in each group at random, usually by computer selection. Double blind means that neither the volunteer or the researcher know before and during the trial whether the volunteer is given the study medication or placebo. This eliminates bias but not the placebo and nocebo effects. The nocebo effect may cause the percentage of negative side effects to be overestimated.

The word nocebo comes from the Latin “nocere,” which means “to harm.” Placebo comes from the Latin “placere” meaning “to please.” The mechanisms of the nocebo effect are not well understood. Studies on the subject have shown that there are a number of contributing factors, among which are: it is more common in women; people with anxiety and depression seem more susceptible to it, as are those with aggressive, competitive, or hostile personalities; pessimists are more susceptible to it; the nature of the physician - patient relationship and the way the proposed medication or treatment is presented to the patient are important factors.

In 2012, the Technical Institute of Munich, Germany, published an extensive review of 31 different studies of the nocebo effect. They concluded that, although puzzling, the nocebo effect was surprisingly common and can affect medical professionals in their daily practice. They found that the suggestion or expectation of pain elicited more negative responses from study participants. In one study, 50 patients with chronic back pain were given a flexibility test. Half were told that they might experience some pain and the other half were not told this. Afterward, the first group reported significantly more pain than the group that was kept in the dark.

Physicians face a conundrum because of something called informed consent. Legally, physicians are required to tell patients about all positive and negative aspects of a proposed medication or treatment, including possible side effects. Likewise, anyone picking up a prescription from the pharmacy is now given pages of information about potential side effects. If the patient reads this information, it is guaranteed to scare the hell out of them. Physicians need to stress the positives while speaking to a patient while still giving the patient all the information required in informed consent, no easy task. Just goes to show that with all the progress we have made, we still have a lot more to learn about the mysteries of human healing.

Questions or comments may be sent to This email address is being protected from spambots. You need JavaScript enabled to view it.

 By Peter Galvin, MG

Sign up via our free email subscription service to receive notifications when new information is available.