The purpose of this blog is to discuss the science of placebo and why you should care.
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When you hear the word “placebo,” do you think about a sugar pill?
Or maybe you think of this scene from Space Jam.
The power of placebo in this scene had nothing to do with the substance itself, which was just water, but the expectations of the players to whom it was provided.
In a healthcare setting, placebo effects can be enhanced by various contextual factors:
- Do you expect the treatment to work?
- Is the treatment highly marketed and supposedly cutting edge?
- Does your provider seem knowledgeable and trustworthy?
- Do they listen and maintain eye contact?
- Is the office clean and relaxing?
These contextual factors can involve conscious or unconscious processes. They can also be conditioned or learned.
Do you expect that hands-on treatment from your physical therapist to reduce your symptoms because it has in the past?
Or do you expect that kinesiotape to help because you saw your favorite athlete wearing it in the Olympics?
If we look beyond placebo effects for a moment, many conditions have a natural history, which means that they often get better on their own.
There’s a funny saying in medicine that makes this concept easier to understand – “..if you treat a cold it will disappear in a week, but if you leave it alone it will last for seven days.”
This is true for many of the first-time symptoms that bring you to see a physical therapist. Regardless of what’s done, you might have gotten better anyway.
Regression to the Mean
There’s another phenomenon to consider known as “regression to the mean.”
Let’s say that over the course of a year, I shot 10 free throws per day and my average accuracy was 70%. If I made 10 out of 10 shots today, what do you expect my accuracy to be tomorrow? What if I made 5 out of 10 shots today?
In both cases, it’s safe to guess that I would make 7 out of 10 free throws tomorrow.
This is common for certain conditions. For example, the symptoms of osteoarthritis generally fluctuate over time. You might typically report your symptoms to hover around a 3/10. However, some days you might report an 8/10 and other days you might not notice your symptoms at all. In either scenario, it’s likely that you’ll eventually return to your setpoint of 3/10.
Correlation is Not Causation
Let’s imagine a scenario in which you come to see me for your low back pain, I provide an intervention, and your symptoms improve dramatically within a few days. It would be easy for us to attribute your reduction in pain to the treatment I provided.
This is a fallacy known as post hoc, ergo propter hoc, which translates to “after this, therefore because of this.” I provided a treatment (X). Your symptoms improved (Y). Therefore, X caused Y.
But this doesn’t take into account everything I’ve already mentioned. There may have been specific effects from my treatment that contributed to your improvement in symptoms, but we also have to consider the natural history of low back pain, regression to the mean, and contextual factors, such as your beliefs, expectations, previous experiences, etc.
If your symptoms improved though, why does any of this matter?
Because everything has a cost, whether that’s money, time, or associated risks.
Kinesiotape is no better than placebo for pain, performance, or injury prevention. If you’re aware of this information, but you still use kinesiotape because it helps you, that’s completely fine. It’s low cost, low risk, and takes minimal time to apply yourself.
But what if the cost, time, and risks increase? For example, a PRP injection is no more effective than a saline injection for patellar tendinopathy.
And what if we take it one step further? Real surgery for shoulder impingement provides no additional benefit than fake surgery.
Any treatment can “work,” but it’s important that research is conducted that controls for natural history, regression to the mean, our biases, and these contextual factors, so you aren’t wasting time or money, or taking unnecessary risks, on something that doesn’t have any specific effects.
If a healthcare provider promises a quick fix, a guaranteed solution, or requests that you see them 3 times per week for 6 months, consider this information and ask questions. Although experience is valuable, if that’s the only rationale for their treatment, you should be skeptical. At the very least, ask yourself – “Are there any other explanations for why this treatment might help?”
The last thing I want to mention is nocebo effects, which are the contextual factors that can worsen outcomes. Do any of these sound familiar?
“That’s the worst knee I’ve ever seen.”
“Your hips are out of alignment.”
“Your rotator cuff is impinging whenever you lift your arm up.”
If your healthcare provider ONLY tells you information that increases your fear, anxiety, or stress and increases your dependency on them, I’d try to find someone else who will lift you up and empower you instead.