Nocebo

What it is

The clearest recent demonstration is the SAMSON trial at Imperial College London. Sixty people who had stopped statins because of side effects were randomised to rotate through periods on a statin, on an identical placebo and on no tablet, scoring symptoms daily; 49 completed it. Average symptom scores were 8.0 with no tablet, 15.4 on placebo and 16.3 on the statin. About 90 per cent of the symptom burden on the statin also appeared on placebo, and half of the sixty later restarted statins.

David Robson's The Expectation Effect treats nocebo across two chapters, citing adverse events reported by people taking placebo across more than 1,200 trials. A 2020 review by Luana Colloca and Arthur Barsky in the New England Journal of Medicine covers placebo and nocebo together.

In effect

Information shapes experience. Warnings, leaflets and stories tell people what to watch for, and people who have been told a tablet may cause aches are more likely to notice ordinary aches and attribute them to the tablet. That leaves a genuine dilemma: people have a right to know side effects, and the knowing can produce some of them.

What it does not say

It does not mean symptoms are imaginary, or that people reporting side effects are making them up.

It does not mean any individual's symptoms are nocebo. Some people have genuine side effects, some serious. Never stop or change a medicine without talking to a doctor or pharmacist.

It does not support claims that belief alone can kill. The evidence is for symptom report, discontinuation and non-adherence.

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