Patients in clinical trials should be given the full benefit of informed consent by raising their awareness of the significant and sustained effects placebo treatments, as well as active drugs, may have on them in this setting, researchers from the UK and the US have concluded.

In a study published in the open-access journal PLoS One, a research team from the University of Southampton, Northern Arizona University and Harvard Medical School in Boston looked at the wording of 45 information leaflets for patients taking part in clinical trials that were placebo-controlled and listed on the database of the National Institute for Health Research’s Clinical Research Network in the UK.

Among the key findings were:

• There was an emphasis on the active treatment being more desirable than the placebo.

• Active treatments were widely described as “real”, “genuine”, and as the focus of the trial. Placebos were rarely characterised in their own right. Instead, they were mostly referred to in comparison with target treatments.

• Active treatments were often described in relation to a class of drug, thereby implying a particular effect – for example, antibiotics (fighting infection) or statins (lowering cholesterol).

• Placebos were often described in negative terms, such as “dummy” or “fake”.

• The information leaflets emphasised both the potential benefits and adverse effects associated with the active treatment. But they largely ignored any effects that might result from taking the placebo.

Consistently prioritised

The study found that active treatments were consistently prioritised over placebos in information leaflets, from the words in the leaflet titles to the description of the trial process, and right through to explanations of what would happen at the end of the study.

According to George Lewith, Professor of Health Research at the University of Southampton, studies conducted at the university have “clearly shown placebos can help about half of the people we treat with chronic pain and can be effective for a long time afterwards”.

The placebo effect is achieved by releasing the body’s own natural painkillers into the nervous system, Lewith adds.

Informed consent

Writing in PLoS One, the researchers argue that volunteers for clinical trials should be more fully informed about the health changes they might experience when taking a placebo.

Otherwise, the researchers believe, patients’ informed consent is jeopardised. Different ways of describing placebos, both in information leaflets and personal interactions with those conducting the research, need to be developed and tested, they suggest.

“We believe the health changes associated with placebos should be better represented in the literature given to patients before they take part in a clinical trial,” comments Dr Felicity Bishop, lecturer in psychology and lead researcher at the University of Southampton.