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Editorial: Could informed consent be harmful? – the problem of the nocebo effect

There are a variety of ways harm can happen in medical research, from physiological reactions, interactions with existing medication or co-morbidities, researcher error to harms occurring because the research participants expect them to. These harms are referred to as nocebo harms, in effect the dark side of placebo effects. Like placebo effects, nocebo effects are caused by psychological factors but can have profound physiological impacts for research participants. While it is likely that differing physiological conditions are more or less susceptible to nocebo effects, there have been some profoundly worrying examples. For example, one study of beta blockers found that the number of research participants suffering the side-effect of erectile dysfunction varied significantly depending on the content of the information sheet. Information sheets that excluded any mention of a risk of erectile dysfunction led to patients reporting this in only 3% of cases, whereas information sheets that included this risk led to patients reporting erectile dysfunction in 30% of cases (Wells and Kaptchuk, 2012). Now there are, of course, multiple interpretations available for this data − erectile dysfunction is, after all, notoriously sensitive to psychological effects, and this might also be somewhat explained by having the risk included in the information sheet serve as a prompt so that more of the second group reported their difficulties than in the first group. Nonetheless, the nocebo effect seems relatively well established if only murkily understood in the literature, having an effect on pain levels, nausea, heart attack risks and many others.