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If there is one thing you want to take from a trip to your doctor, she is optimistic.
A new study, published Monday in the journal Nature Human Behavior notes that patients may choose to become familiar with subtle facial signals from physicians that reflect the physician's belief in efficacy clarify a treatment. And that can have a real impact on the patient's outcome.
Scientists have known since at least the 1930's that the expectations and personal characteristics of a physician can significantly affect a patient's symptom relief. In research, avoiding these placebo effects is one of the reasons for double-blind studies – to prevent experimenters from inadvertently distorting their results with telegraphs on subjects, which they expect from the results of a study.
The new study proves that the placebo effect is transmitted from the doctor to the patient and shows how he may be acting. Randomly, the researchers chose students who play the role of a patient or a physician. The "patients" received a controlled thermal stimulus to the forearm after receiving one of two types of cream from the "doctor."
Students in the medical group had previously been conditioned to believe that one of the creams is a painkiller. In fact, both creams administered were an identical, petrolatum-based placebo. And yet, when the doctors 'actors thought the cream was a real drug – the researchers even called the pseudo-medication "Thermedol" – the patients' actors reported that they had significantly less pain.
As well documented as the placebo effect is, the authors of the study were surprised that it was so clean. "We did more research to convince ourselves that it was not just a coincidence," said lead author of the study, Luke Chang of Dartmouth University. "I am impressed by how robust the effect seems to be."
Once they were sure that their study demonstrated the placebo effect at work, researchers could ask the question that interested them most: how do patients experience what their doctors expect as a result of treatment?
Using head-mounted GoPro cameras to collect video from study participants, the study fed the footage to a computer model that analyzed the intensity and type of facial expressions known as facial units and correlated facial features such as lip curling. Wrinkles in the nose and eyebrows lower with the experience of pain.
The model found that while administering the pain stimulus, the physicians group showed measurably less facial pain when they believed that the patients had been given a cream that provided real pain relief. As this happened, the patient group also seemed to have less pain. The students in this group showed less painful facial expressions and had less pain from other measures. In studies where the group of physicians believed the cream was effective, patients reported that they found the physicians more empathetic.
According to Chang, the paper proves that subtle, non-verbal factors "can have a major impact on pain perception," and he hopes his study will encourage more research into the mechanisms that lead to pain relief alongside medications.
The psychologist Harald Walach from the Medical University of Poznan in Poland, who was not involved in the study but wrote an accompanying commentary, finds the parallel experience of physicians and patients in treatment and placebo groups "fascinating".
"A lot of self-healing is more driven by expectations than medication," he says. "In therapeutic processes, much happens by giving the patient expectations and hopes, and not necessarily treatment as such."
"This finding is a bit painful for doctors," he says.
One specific area in which Chang would like to see more studies is the interpersonal expectation effect – a well-documented phenomenon where expectations influence outcomes. He refers to a study from 1964, which found that rodents went through a labyrinth measurably faster than experimenters believed that these rats were bred smarter. In such cases, he says, "we know something happens, but we do not know why."
Lauren Atlas, a neuroscientist and pain researcher at the National Institutes of Health who was not involved in the study, believes the research could have lessons for people working in pain research. "We'll benefit a lot from studying interpersonal issues and how they shape pain," she says. She says, for example, that it can have a significant impact on the outcome of treatment, whether doctors and patients are a good match or not.
Walach is pleased that the placebo effect is being taken seriously. "It used to be a grinning field." The word "placebo" has been used more derogatively, he says, "but it is beginning to be understood that these effects are very strong and that we can use them for the benefit of humans."