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Nocebo Effects

Posted by Nicholas Dang on
Nocebo Effects

Here is a real story…

Mr A, a 26-year-old male, presented to an emergency department saying, ‘Help me, I took all my pills’, and then collapsed. As he fell, he dropped an empty prescription bottle.

He had taken all of his medication, which he said was a new experimental drug for depression. The bottle contained capsules to be taken as part of a research trial of an antidepressant medication, but the bottle did not say whether he received the active medication or placebo.

Mr A had been depressed for about 2 months after his girlfriend broke up with him. Subsequently, he felt hopeless and joined a research trial for a new antidepressant at a large university. During the first month of the trial, he felt that his mood improved significantly. He had just started his second month in the trial when he took all of the remaining 29 capsules after an argument with his girlfriend.

When he was assessed, he was pale and he had low blood pressure and high heart rate. He was shaking and breathing rapidly. Over 4 hours, he received treatment but he remained lethargic and his blood pressure and heart rate were still irregular.

However, a physician from the research trial arrived and determined that Mr A had taken placebos. When Mr A was told this, he was very surprised and relieved. Within 15 minutes, he was fully alert and his blood pressure and heart rate returned to normal.1

‘Nocebo’ refers to the negative effects of an inert treatment (in contrast to ‘placebo’, which refers to positive effects).

Nocebo effects may occur if we expect unfavourable outcomes. For instance:

  • If you believe you will hurt your back when lifting because you were told that lifting is bad for your back, then your pain/nervous system is more likely to produce or amplify pain (even if your back and spine are robust—which is true—and can physically tolerate lifting).
  • If you have been told that sitting is harmful but you have to sit a lot for study or work, then this may sensitise your body. It is normal to feel discomfort after prolonged sitting (your body is telling you to move) but because you have negative expectations, you may experience pain sooner and/or higher in intensity.

Many things we hear and see can promote a placebo or nocebo effect.

Can you think of times when you have been placebo-ed or nocebo-ed?



  1. Reeves et al. (2007) (PMID: 17484949)

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