A new study suggests that, through neuroimaging, a placebo reduces pain in the same way as distracting the person who is in pain.
In both situations, scientists observe brain activity in the dorsolateral prefrontal cortex — the part of the brain that controls high-level cognitive functions like working memory and attention.
Now, however, a new study challenges the theory that the placebo effect is a high-level cognitive function. The results could help clinicians maximize pain relief without drugs.
For the study, researchers reduced pain in two ways — either by giving participants a placebo or a difficult memory task.
But when they put the two together, “the level of pain reduction that people experienced added up. There was no interference between them,” says Jason T. Buhle of Columbia University. “That suggests they rely on separate mechanisms.”
For the study, 33 volunteers attended three separate sessions. In the first, researchers applied heat to the skin with a small metal plate and adjusted each person’s pain perception. In the second session, some of the subjects were given an ordinary skin cream but were told it was a powerful but safe analgesic. The others applied the cream and were told it was regular hand cream.
In the placebo-only trials, volunteers stared at a cross on a screen and were asked to rate the pain of numerous heat applications — the same level of pain, although they were told it varied.
During other trials they were given a tough memory task — distraction and placebo simultaneously. For the third session, individuals who had been given the plain cream received the “analgesic” and vice versa. The procedure was the same.
The results show that when either the memory task or the placebo was given alone, volunteers felt less pain than during the trials when they just stared at the cross. Together, the two effects added up and did not interact or interfere with each other. This suggests that the placebo effect does not require executive attention or working memory.
“Neuroimaging is great,” says Buhle, “but because each brain region does many things, when you see activation in a particular area, you don’t know what cognitive process is driving it.”
The findings are promising for pain relief. Clinicians utilize both placebos and distraction—for example, virtual reality in burn units, but it has been unclear if one could diminish the other’s efficacy. “This study shows you can use them together,” says Buhle, “and get the maximum bang for your buck without medications.”
The research is published in Psychological Science.
Photo courtesy of Science Photo Library.