The Independent, 4 March

Placebos can be just as effective as anti-depressants. Five years ago, Italian researchers carried out tests on patients recovering from serious operations, needing morphine to dull their pain and diazepam to calm their nerves. Patients received their medicine automatically through intra-venous drips, but were not told when the drugs were being administered. The scientists found that not being told that they were receiving morphine cut the effect of pain relief on the patients in half. Those who were given diazepam without being told did not get calmer at all.

The placebo response is extremely powerful. If we believe we are getting heavy treatment then we automatically feel better, even if there is nothing in the medication at all. The larger and more dramatic we perceive the intervention to be, the greater the impact. For this reason, placebo morphine is far stronger as pain relief than placebo aspirin – though both contain no medicine.

Last week, Irving Kirsch, professor of psychology at the University of Hull, and his team, discovered that leading brands of modern anti-depressants work only slightly better than placebos in all but the most serious cases of depression. Reports concluded that anti-depressants may be useless, but that response to placebos was exceptionally large. However, this does not indicate the failure of anti-depressants, but more the potential for placebos to work very well.

The placebo effect is not just confined to medicines. Sham operations for angina and knee surgery, where the knee is only punctured, is just as successful as the real thing. According to one study, painting warts with brightly coloured dye and telling them their warts will go when the dye wears off is also effective.

It is remarkable that such fakery should be so powerful. The placebo effect means up to 75 per cent of patients improve on a dummy pill, sometimes for years at a time. So how does it work? There are many theories circulating, including Boston psychologist and physician, Dr Richard Kradin’s notion that the key to the placebo effect lies in the relationship between patient and doctor, or therapist. A leading researcher in the field, Kradin’s book The Placebo Response and the Power of Unconscious Healing argues that even a trusted friend can trigger the placebo response. ‘It needs to be someone who you trust, who you have some confidence in and who proposes they have something to offer you. For many people that’s enough.’

However, placebos work best for conditions with a subjective element to them – depression, anxiety, irritable bowel syndrome and pain. It can’t cure sugar blood levels, a broken leg, or pneumonia – although Dr Kradin believes spontaneous remission may be down to placebos. ‘Doctors need to be aware that how they interact with their patients has a great deal to do with the outcomes they are going to get.’ Maybe placebos are just the trick.