People overestimate the benefits and underestimate the risks of medical interventions

From major heart surgery to drugs for a minor ailment, people overestimate the benefits and underestimate the risks of medical procedures.

This could mean patients have unrealistic expectations about the treatments they are offered, according to Dr Jonathan Rolison, from our Department of Psychology.

In a study involving 376 adults, participants were asked to imagine their doctor had recommended a treatment for different conditions – a drug for an eye infection, surgery for a gum infection, burst eardrum and a benign growth and a newly-developed medication for a life-threatening blood disorder.

In each scenario they were provided with precise information about the probability of success (for example saving a tooth) and the probability of the risks (such as liver damage). The treatments and side effects were taken from medical studies, but the probabilities of them happening were devised by the study authors for the purposes of the research.

Participants were then asked to indicate how likely they believed they were to experience one of the benefits or risks by moving a pointer on a scale from 0% to 100%.

Dr Rolison said: “On average, participants were overly optimistic about the treatment outcomes, underestimating their chances of experiencing the side effects of a treatment and overestimating their chances of experiencing its benefits.

“The findings have worrying consequences for clinical practice. Patients are encouraged to make informed decisions, which may involve deciding on a cancer treatment. Our study shows that patients may have unrealistic expectations about such treatment options.”

Results showed on average people perceived the benefit as higher than the benefit midpoint – in the case of the tooth, the perceived likelihood of benefit was 48%, compared with the midpoint of 45%.

In contrast risks were underestimated. The biggest difference was regarding a kidney operation for a benign growth, where the perceived risk of the possible side effect, paralysis (43%) was significantly lower than the actual risk (53%).

Lead author Professor Yaniv Hanoch, Professor of Decision Science at the University of Plymouth, said: “These were really interesting results. By presenting participants with a wide range of medical scenarios – including minor and serious ones, as well as physical, psychological, and dental – our findings lend support to a growing body of evidence regarding unrealistic optimism.

“From an applied perspective, these results suggest that clinicians may need to ensure that patients do not underestimate risks of medical interventions, and that they convey realistic expectations about the benefits that can be obtained with certain procedures. It would be good to carry out further studies on a larger population and also explore if and how clinicians can help manage expectations.”

The study, which also involved Alexandra Freund from the University of Zurich, was published in the journal Risk Analysis.