Poor expectations of treatment can override all the effect of a potent pain-relieving drug, a brain imaging study at Oxford University has shown.

In contrast, positive expectations of treatment doubled the natural physiological or biochemical effect of the opioid drug among the healthy volunteers in the study.

The study of the placebo effect — and its opposite the nocebo effect — is published in Science Translational Medicine. The findings suggest that doctors may need to consider dealing with patients’ beliefs about the effectiveness of any treatment, as well as determining which drug might be the best for that patient.

‘Doctors shouldn’t underestimate the significant influence that patients’ negative expectations can have on outcome,’ says Professor Irene Tracey of the Centre for Functional Magnetic Resonance Imaging of the Brain at Oxford University, who led the research.

For example, people with chronic pain will often have seen many doctors and tried many drugs that haven’t worked for them. They come to see the clinician with all this negative experience, not expecting to receive anything that will work for them. Doctors have almost got to work on that first before any drug will have an effect on their pain.’

The placebo effect describes the improvements seen when patients — unknowingly — are given dummy pills or sham treatments but believe it will do them good. This is a very real physiological effect; it is not just about patients ‘feeling’ better. The nocebo effect is the opposite: patients see poorer outcomes as the result of doubts about a medical treatment.

Previous studies have investigated the basis of the placebo effect, when using sugar pills or saline injections for example, and confirmed it can elicit a real response.

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