A person’s susceptibility to the placebo effect can vary based on certain personality traits, according to a new international study.
The research was based on a relatively small group of participants, and showed that about one-quarter of the effect is linked with resiliency, straightforwardness, altruism, and anger.
“We started this study not just looking at measures that might seem more obviously related to placebo responses, such as maybe impulsivity, or reward-seeking, but explored potential associations broadly without a particular hypothesis,” said study co-author Jon-Kar Zubieta at the University of Michigan in a press release.
“We ended up finding that the greatest influence came from a series of factors related to individual resiliency, the capacity to withstand and overcome stressors and difficult situations.
“People with those factors had the greatest ability to take environmental information—the placebo—and convert it to a change in biology.”
The team tested nearly 50 healthy male and female volunteers aged 19 to 38, using standard psychological tests to identify personality traits.
They then imaged the subjects’ brains with a positron emission tomography (PET) scanner while injecting their jaw muscles with salt water to cause pain, followed by a so-called painkiller—which was actually a placebo—during a 20-minute period.
The scans showed the level of natural painkillers released by different parts of the brain, and blood tests were used to measure the levels of the stress hormone cortisol.
These results were analyzed in relation to the personality traits, and showed that angry hostile types had the least effects from the placebo.
Natural painkiller levels and patient-rated pain intensity levels were influenced by personality traits and the placebo effect, but cortisol levels did not seem to be affected.
The findings could apply to other stress-inducing circumstances, and were published in Neuropsychopharmacology on Nov. 16.
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