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Unnecessary Harm Caused by Informed Consent

10 May 2021

The Medical Research Council (MRC) has funded a project to reduce unnecessary harm caused by the way potential trial harms are communicated to potential patients.

Making informed consent more ethical

Patients need to be informed about potential risks of taking part in clinical trials. A problem is that there are no standards telling researchers or ethics committees how these risks need to be communicated. The research team’s background research suggests that the way harms are communicated can actually increase the risks of the harms occurring. Over half of their sample of 250,000 patients who took placebo pills (like sugar pills) in clinical trials reported some negative side effect (like pain or nausea but also more serious things). Their sample of information leaflets provided to patients also found that potential trial benefits were sometimes not mentioned, with potential harms being emphasized.

The MRC has funded the team, based at Cardiff University (and including researchers from Manchester University, and the University of Aberdeen) to investigate ways to share potential trial harms honestly and completely, yet in a balanced way that does not actually cause unnecessary harms. With input from real patients, trial researchers, industry, and legal experts, they will develop new ways of sharing information about potential trial benefits and harms. They will then test these in five clinical trials, to see whether they reduce harms.

The output of the project will be a set of Principles for Patient Information Leaflets (PrinciPILs), which will help trialists design information about potential trial risks and benefits in an ethical and balanced way that does not cause unnecessary harm. PrinciPILs will also save time because researchers and ethics committees won’t have to reinvent the wheel whenever they are thinking about ways to present potential trial risks and benefits. As one of the reviewers of this project stated, this ‘should have been addressed years ago’.

The Nocebo effect

The nocebo effect (the effect of expecting a negative outcome) has been almost ignored. Epistemic and ethical confusions related to its existence have gone all but unnoticed. Contrary to what is often asserted, adverse events following from taking placebo interventions are not necessarily nocebo effects; they could have arisen due to natural history. Meanwhile, ethical informed consent (in clinical trials and clinical practice) has centred almost exclusively on the need to share intervention risks with patients to preserve their autonomy. Researchers have failed to consider the harm caused by the way in which such risk information is shared. The magnitude of nocebo effects must be measured using control groups consisting of untreated patients. And, because the nocebo effect can produce harm, the principle of non-maleficence must be taken into account alongside the principle of autonomy when obtaining (ethical) informed consent.


Medical Research Council, award number MR/V020706/1


For further information or comment, please contact Dr Jeremy Howick, (senior research and principal investigator or Professor Kerry Hood (