British psychologist and journalist Christian Jarrett has written a detailed and up-to-date summary at BPS Research Digest, a news website of the British Psychological Society, of what we currently do — and don’t — know about the “mysterious and maddening” placebo effect.
As Jarrett notes, the term placebo effect “is short-hand for how our mere beliefs about the effectiveness of an inert treatment or intervention can lead to demonstrable health benefits and cognitive changes — an apparently incontrovertible demonstration of the near-magical power of mind over matter.”
The mysterious part of the placebo effect is that it works at all. The maddening part is mainly a matter for researchers, who view the placebo effect as “a methodological nuisance,” as Jarrett puts it.
“Researchers must go to extreme lengths to rule out the influence of participant expectations, so as to establish which observed effects are truly attributable to an intervention,” he writes.
In his article, Jarrett describes (with British spellings and punctuation) 10 of the more amazing placebo-related findings, including three excerpted here:
The placebo effect works even when you know it’s a placebo
For the placebo effect to occur, it’s usually considered that deception is required — tricking the patient into thinking that an inert treatment is actually a powerful drug or similar. It’s this need for trickery that has long meant the deliberate inducement of placebo effects in mainstream medicine is seen as unethical. Nearly ten years ago, however, researchers showed that people with irritable bowel syndrome showed greater improvement after being given a so-called “open placebo” that they were told was completely inert, as compared to receiving no treatment. … More recent research has since shown benefits of open placebos for many other conditions including back pain and hay fever. …
Some people are more prone to the placebo effect than others
Certain personality traits are associated with it being more likely that a person will experience the placebo effect. This is logical since the placebo effect depends on our beliefs and expectations, which some of us may subscribe to more readily and enthusiastically than others. Among the results in this area, optimists are more responsive to analgesic placebos, as are people who score higher for emotional resilience and friendliness (this last finding may relate to the social dynamic involved in the elicitation of the placebo effect by physicians). Curiously, the traits related to placebo response vary according to the condition being treated – in the context of stress, for instance, one study found it was the more pessimistic and less empathic participants who showed a greater placebo response. …
The placebo effect has an evil twin
If the placebo effect occurs simply because you believe a given treatment will be beneficial, it follows that if you have negative expectations, this could result in a worsening of your symptoms. That’s exactly what researchers have found and they’ve called this the “nocebo effect”. The placebo effect’s twin is not to be sniffed at either. A meta-analysis in the context of analgesia (in which some participants are told that an inert cream or pill leads to increased pain in some people) found that the nocebo effect is roughly similar in size to positive placebo effects.
Intriguingly, nocebo effects can even occur in the presence of real pain-relieving medications, not just inert treatments — in one study, participants were told that their pain would increase after an analgesia treatment was stopped. The physiological effect of the analgesia would normally persist, however in these participants it ended abruptly, as if the negative expectations had cancelled out the genuine analgesic effect. …
Here are other placebo-related findings that Jarrett covers in his article:
- Branding, Colours and Medical Paraphernalia Can All Boost the Placebo Effect
- Some Doctors Are Better at Inducing the Placebo Effect than Others
- There’s Even Such a Thing as Placebo Sleep
- Animals Seem to Experience the Placebo Effect Too
- The Placebo Effect Is a Bit of a Pain for Many Psychology Researchers
- The Placebo Effect Appears to be Getting Stronger
You can read about all of them on the BPS Research website.