We’ve probably all heard of the placebo effect, but what is it, and how does it work? For something that happens regularly, it’s not all that well understood.
A placebo is any substance that’s not intended or expected to have any therapeutic effect. Ethically, it generally wouldn’t be considered acceptable to give a patient a placebo in clinical practice, since there would be no informed consent.
Placebos are very useful in research studies, though. As part of the consent process to enrol in a study, participants would be informed that they could potentially receive a placebo or an active drug, but they wouldn’t know which. In a “double-blinded” study, neither the patient nor the researchers dealing with them would be aware of whether the patient received the active drug or a placebo. Wikipedia says that a doctor named Louis Lasagna helped to make placebo-controlled clinical trials the norm in the US; I must say, I’m somewhat tempted to change my last name to Lasagna.
Professor Ted Kaptchuk, a placebo effect researcher at Harvard University, says:
“The placebo effect is more than positive thinking — believing a treatment or procedure will work. It’s about creating a stronger connection between the brain and body and how they work together,”
Harvard Health Publishing
I think that’s a very interesting way of framing it.
The effects of placebos
When placebos do have a benefit, it tends to be in terms of subjective symptoms rather than a change in underlying disease processes. Pain is the most common type of symptom that responds to placebos. It’s not that pain isn’t real, but the way it’s experienced depends on how pain signals are managed in the brain.
For people with cancer, a placebo isn’t going to change the disease process and certainly isn’t going to cure their cancer. However, it may help lessen side effects like fatigue and nausea from cancer treatment.
Placebo can also help with stress-related insomnia. An interesting study cited by Wikipedia found that people believed that they were sleeping better while taking a placebo, but objectively, there was actually no change in their sleep.
Placebos can also be associated with negative effects, which is called a nocebo effect. This doesn’t seem surprising, given how problems in the head can wreak havoc on the body.
What’s behind the placebo effect
Some of the benefit from placebos seems to be linked to expectancy. If you expect that something is likely to work, you may start to feel better after taking it. On the other hand, if you expect negative effects, you might be headed for nocebo effects. Expecting pain actually makes the brain more sensitive to pain signals.
Conditioned responses can occur when taking a placebo becomes associated with taking actual treatment. This can happen if, for example, the pill or capsule looks similar to an actual treatment. Think Pavlov’s dogs, where the bell is the placebo stimulus. Similarly, the routine and attention of getting treatment can also contribute to the placebo effect.
Placebo analgesic effects may result from the release of endogenous opioids and the inhibition of pain signals travelling up to the brain.
Not everyone who improves while taking a placebo is actually experiencing a true placebo effect. Some people may have gotten better due to the natural course of their condition; the fancy term for that is regression towards the mean. To differentiate between the two, a study might compare one group of patients getting a placebo and another getting no intervention. When clinical drug trials are done, it doesn’t add any new information about the drug to add a no-treatment arm in addition to the drug and the placebo arms; therefore, the placebo response rates encompass both placebo and regression towards the mean.
Do alternative therapies rely on the placebo effect?
It’s quite possible that some alternative remedies that haven’t demonstrated efficacy in clinical trials may be beneficial via a placebo effect.
It’s also possible that traditional or alternative therapies may exert a physiological effect via a mechanism other than what’s traditionally been claimed. For example, there’s no evidence that acupuncture works by affecting qi, the existence of which hasn’t been proven. However, it does appear to have a therapeutic effect related to the gate-control theory of pain.
The key thing, though, is to make sure that there isn’t an underlying issue that’s going unaddressed because of reliance on something that might just be a placebo. Relying on the placebo effect of psychic surgery to treat a tumour just isn’t going to cut the mustard. On the other hand, if someone is having reiki for chronic pain, whether there’s an effect via a placebo effect or something beyond that really doesn’t matter that much, since there’s a plausible potential for benefit with little to no risk. The claims just need to match the reality.
As long as no one is trying to trick anyone or make things up, I say bring on the placebo. The brain and body are intimately interconnected in ways science hasn’t fully figured out, so why not take advantage of that as long as there’s no risk involved?
References
- Cancer.org: Placebo effect
- Harvard Health Publishing: The power of the placebo effect
- Wikipedia: Placebo effect
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