The title was on the cover of the April 2015 Monitor on Psychology of the American Psychological Association. Inside the issue was an article by Stacy Lu, “Great expectations: New research is leading to an understanding of how placebos work—findings that may lead to more effective treatments and better drug research. Our understanding and attitudes towards placebos is advancing.
In one study neuroscience researcher Shaffer and his colleagues asked participants to apply a “powerful analgesic” on their hands and arms. Then the researchers administered small bursts of heat where the cream had been applied. The cream was actually petroleum jelly, but participants reported that the s-called powerful cream protected them from feeling as much of a burn as a control cream. Even after the researchers showed them that the active cream was just petroleum jelly, it made little difference. The participants still reported less pain from the heat when they were re-tested versus the control cream (The Journal of Pain, 2015).
Today scientists are studying placebos as a psychobiological phenomenon and the placebo response as a potentially important part of the success of many medical treatments. Psychological assessments, brain scans, and genotyping are used to understand better how placebo responses work and to identify who may be most likely to respond to them. Placebos are similar to cognitive therapies in that they tap into people’s beliefs that there’s hope and that they will get better.
A meta-analysis of 25 neuroimaging studies of pain and placebos conducted by Wager and Atlas of the National Center for Complementary and Integrative Health (NCCIH) found that people who took placebos and expected have reduced pain had less activity in brain regions associated with pain processing, including the dorsal anterior cingulate, thamalus, and insula (Handbook of Experimental Pharmacology, 2014).
Research suggests that placebos have the greater effect in neural systems involved with processing reward seeking, motivation, and emotion. Placebos seem to work especially well in patients with depression, Parkinson’s disease, and pain. All three conditions involve the neurotransmitter dopamine. These are also areas where people can consciously monitor their own treatment results.
In a study of patients with Parkinson’s disease Wager and colleagues found that simply expecting medication altered brain activity in the striatum and ventromedial prefrontal cortex in brain areas associated with reward learning in ways similar to actual dopaminergic medication (Nature Neuroscience, 2014).
In another study of people with migraines, placebos elicited a response without any verbal cue to effectiveness, Slavenka Kam-Hansen and colleagues openly labeled placebo pills for some patients who reported as much pain relief as those who also got a placebo but had been told that they’d received real medication. (Science Translational Medicine, 2014).
Genetics research has found that participants with a specific genotype related to having more dopamine in the prefrontal cortex reported having a larger effect from a placebo treatment than participants with a genotype that produces less dopamine in the prefrontal cortex (PLOS ONE, 2012).
Children seem to respond especially well to placebos. In one study their placebo response was 5.6 that of adults (The Journal of Pain, 2014).
Patients are interested and enthusiastic about placebo treatments. They are pleased to discover that they can contribute to their own healing.