The Power of Nocebo Effect

Posted on July 24th, 2013

You have probably heard about a placebo effect where a sugar pill is given to a person, which can cause perceived or actual improvements in the person’s condition. Even more surprising is that the type of side effect a placebo can cause will vary depending on the perception of the drug being tested.1

However, most people are not aware of the twin opposite of a placebo - a nocebo effect. In Latin, nocebo means “I will harm” while placebo means “I will please”. A placebo can improve healing or pain reliefs, whereas a nocebo can make people feel bad and worsen the negative symptoms.

The Five Components Of Nocebo Effect

“The perception of pain can be strongly influenced by people and the environment. Placebo and Nocebo can influence people’s experience on a neuroanatomical and neurobiological level and have a strong impact on people’s ability to harness positive and minimize negative effects therapeutically.2

1. Psychology

Stress, anxiety, and depression, can increase susceptibility to the nocebo response. Prolonged symptoms of stress can lead to psychosomatic health problems where a physical problem is caused or strongly influenced by a psychological problems.

2. Conditioning

Does Ivan Pavlov ring a bell? Negative experiences and developed side effects from the past are often associated with visual, auditory, kinesthetic and other cues. For example, some cancer patients experience nausea or even vomit when they enter a room where they have recently had a chemotherapy.

3. Context

Did you know that the packaging of medication can influence how you respond to the medication? Bright colors such as red, orange, and yellow are associated with stimulation and arousal. Darker colors such as blue and green are associated with sedation. Patients who take blue placebo pills are morel likely to say that they feel sleepy comparing to those who take pink placebo pills.

4. The Power Of Suggestion

When doctors describe possible side effects of treatment, they have to be careful about what they say and how they say it because their words can strongly influence the patient’s expectations. Patients view their doctors as authoritative experts. What a doctor may suggest as a possible outcome, can become a self-fulfilling prophecy for the patient.

5. Language

Strong words such as danger, electric shock and pain can actually increase the subjective feeling of pain. Choose your words carefully, they may hurt someone.


The exact mechanism of the nocebo response is still unknown. Placebo activates endorphins in the brain to provide pain relief. It is possible that nocebo activates the receptors in the brain that stimulate the production of stress hormones, which influence the perception of pain. Both effects are unconscious and both can produce  biological changes.

Words can create powerful experiences in people. I think that that healthcare professionals and parents should be especially be mindful about what they say and how they say it. Be careful of what you say to other people because for some of the it come become true.

Have you experienced any placebo or nocebo effects in your life?

  1. New insights into the nocebo response. (2011). Harvard Mental Health Letter, 27(11), 6. 

  2. Tracey, I. (2010). Getting the pain you expect: mechanisms of placebo, nocebo and reappraisal effects in humans. Nature Medicine, 16(11), 1277-1283. doi:10.1038/nm.2229 

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