"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. At the moment these effects are largely being ignored in the patient information leaflets," says lead researcher at Southampton and lecturer in psychology, Dr Felicity Bishop.
She continues, "There is an important issue of consent here – patients should be fully aware of possible health changes from all treatments in a trial before agreeing to take part."
The research team, led by the University of Southampton in collaboration with Harvard Medical School and Northern Arizona University, examined the wording of 45 participant information leaflets from clinical trials which used placebos and are listed on the UK Clinical Research Network Database.
Analysis of the participant leaflets led to these key observations:
Crucially, the study showed the target treatments were prioritised over the placebo, from the words in the leaflet titles, to the description of the trial process, through to explaining what would happen at the end of the trial.
Professor of Health Research at the University of Southampton, George Lewith, comments, "The leaflets largely ignored the overwhelming evidence that placebos can actually have significant and sustained effects on people. This could affect the treatment beliefs and expectations of those volunteering for studies and in turn the results.
"Studies at Southampton 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 works by releasing our bodies' own natural painkillers into our nervous system."
The researchers argue that volunteers for clinical trials should be more fully informed about the health changes they might experience from a placebo, otherwise their informed consent, crucial to taking part, is in jeopardy. They believe different ways of describing placebos need to be developed and tested, both for participant information leaflets and for personal contact with those conducting research.
The research was funded by Primary Care and Population Science, part of the Faculty of Medicine, at the University of Southampton.