The placebo effect works even when people know they are taking a dummy drug, scientists have found, in a breakthrough that could lead to cheap medicines which work by the power of suggestion alone.
Traditionally it was thought that sugar pills were only effective when their clinical inefficacy was hidden from the patient.
However, an intriguing new trial has shown that people still get the benefits even if they know it is placebo, provided they are told they may experience an effect.
Researchers at Harvard University in the US and the University of Basel in Switzerland conducted an experiment on 160 volunteers who were asked to put their arm on a heating plate until they could no longer withstand the pain.
All were then given placebos, but one third of the group were told they they had received the topical painkiller lidocaine to help with the burn. A second group was warned the cream was only a placebo but also given a 15 minute talk explaining how dummy drugs can help. A control group was told they would have a placebo, but without any additional commentary.
The results showed that those who knew about the placebo experienced similar pain relief as those who thought they had been administered with lidocaine. In contrast the control group were left in uncomfortable pain.
“The previous assumption that placebos only work when they are administered by deception needs to be reconsidered,” said Dr Cosima Locher, a member of the University of Basel’s Faculty of Psychology and first author of the study.
Previous studies have shown that placebo medication can have a significant impact on physical complaints, including chronic back pain, irritable bowel syndrome, episodic migraine and rhinitis.
However scientists have struggled to come up with a way to harness the effect without deceiving patients, which would be unethical.
The new study suggests that the placebo effect could still be useful even when patients were told about it, as long as they were given an explanation about how it might bring benefits.
“Openly administering a placebo offers new possibilities for using the placebo effect in an ethically justifiable way,” said co-author Professor Jens Gaab, Head of the Division of Clinical Psychology and Psychotherapy at the University of Basel.
The new research was published in the journal Pain.