Medicine works better the more doctors believe in it, a new study suggests.
Scientists say that when medics are confident in a treatment, patients pick up on subtle inter-personal signals such as a warmer manner and increased eye contact.
A series of experiments at Dartmouth College revealed that this results in decreased levels of pain and better outcomes.
Published in the journal Nature Human Behaviour, the results imply that not only do patients feel better when their doctor has more confidence, the treatment or medicine itself has greater physiological effect.
The research team tested their theory on 24 trial participants, each paired with a person pretending to be a doctor.
Each of the patient participants had an uncomfortable degree of heat applied to their arm.
They were then offered one of two types of soothing cream by the participant playing the part of the doctor.
The pretend doctors had been told by the study organisers that one of the creams was a recommended medicated substance and the other a fake.
However, in reality both creams were unmedicated, simply Vaseline in disguise.
Despite this, patient participants, who had been told nothing about either cream, enjoyed a sharper decrease of pain when applied with the substance the pretend doctor believed was the superior treatment.
This was measured by means of a GoPro camera linked to an artificial intelligence system programmed to interpret signals such as wrinkled noses, raised eyebrows and upper lip movement.
Skin measurements also recorded decreased psychophysiological arousal with this treatment
The experiment was repeated a number of times to vary the order in which the patient participants received the two creams.
Professor Luke J Chang, senior author of the study, said: "These findings demonstrate how subtle social interactions can impact clinical outcomes.
“Even though the study participants were role playing and weren't actual health professionals or patients, you can imagine that in a real clinical context, if the healthcare providers seemed competent, empathetic and confident that a treatment may work, the impact on patient outcomes could be even stronger.”