Reconceptualizing the Placebo Effect

Disclaimer: I read about pain research regularly, but I’m not a doctor/medical professional, and there’s always the chance I’m talking out my own ass. So while perhaps it would be advisable to take the following somewhat with a grain of salt, I will endeavor to make it as accurate and interesting a grain of salt as I am able.

I had a conversation with a friend a while ago about pain. I was talking about the idea that your brain can create pain independent of any actual physical damage to your body. You can hook a person up to a device and tell them it will be, say, running a current through them that is proportionate to how far a dial is turned, and they will report a pain experience proportionate to how far the dial is turned, even when the device does not actually do anything.

Her response to this was, “Oh, yeah, the placebo effect!”

This threw me, because she was absolutely right, but I hadn’t thought about that phenomenon in terms of the the placebo effect in quite some time.

When I think about the placebo effect, I think of it the same way that I think about a computer bug. It’s a mistake, a glitch, an error in the way the system was written. It’s as though the system works in a particular way – that is, it is designed to produce pain in response to physical damage – and the placebo effect is the phenomenon where every now and then the system gets fucked up and overwritten by what we think is actually happening.

That way of thinking about the placebo effect is wrong. It took having this conversation for me to realize that. The placebo effect isn’t a bug in the sense that I was thinking about it. For the most part, it’s a feature. The placebo effect happens as a result of the fact that your brain always, without exception, takes context into account when making a decision about whether or not to create an experience of pain. The fact that it sometimes gets this wrong isn’t because of some random glitch in the system, it’s an inescapable byproduct of how the system fundamentally works. In some sense, every physical experience you have is the placebo effect.

What I mean by that is that every physical experience you have is modulated by context that has nothing to do with what is actually happening to you physically, and everything to do with the associations you have with what is happening to you physically, with contextual cues, et cetera. That isn’t a separate phenomenon, it isn’t something that happens sometimes, it is a basic, core part of how every physical sensation happens (or doesn’t).

Fun example fact: if you prick the finger of a dancer and then of a violinist, there’s a pretty good chance the same prick will hurt more for the violinist. Their finger is more important to their wellbeing, and so the context of the prick is that it represents a greater threat to the violinist, and thus there is a greater impulse to avoid it, and thus the brain will create a correspondingly greater experience of pain1.

It’s time again to review Lorimer Moseley’s snake bite story2,3, because it’s such a perfect illustration of this idea:

Lorimer was hiking with some friends one day and felt a mild twinge on his leg, thought nothing of it, and ended up in a hospital having been bitten by an incredibly poisonous snake. One of the effects of snake venom is that it locks nociceptors into an activated position, so the amount of danger signals sent to the brain would have been massive, and yet when those signals got to the brain, the brain had no historical context to indicate such signals were dangerous, and so did not create a correspondingly massive pain experience. In fact, it created almost no sensory experience at all. As a result, Lorimer nearly died. About six months later, however, Lorimer was hiking again and experienced a sudden, massive pain on his leg in the same place as before, and very nearly ended up taking a trip to the hospital until one of his friends took a glance at the leg and discovered that it was only a tiny scratch from a twig.

In both of those cases, the system failed. When the trigger was a snake bite, the brain did not produce a sensory experience that felt anything like a snake bite. Later, when the trigger was only a twig, the brain interpreted it, mistakenly, as incredibly dangerous, presumably because it then had the context of the near-fatal snakebite informing the sensory interpretation.

So why does this matter? It matters because this model makes it possible to better understand what’s going on with the placebo effect and how the phenomenon of pain being modulated by context can be applied to solving pain problems.

In Lorimer’s story, we have an illustration of both sides of the coin: not having an experience of pain when it would have made more sense to have one, and having an experience of pain when it would have made more sense not to.

Here’s one of the ways I apply this model of thinking: what does it mean when someone says acupuncture cured their chronic pain, given that we know acupuncture performs no better than sham acupuncture in studies4?

The interesting thing to note here is that both the pain and the cessation of pain could have nothing to do with damage to the body. I.e. it is possible to experience chronic pain that is not a result of physical damage, and it is also possible to stop experiencing pain regardless of whether or not any physical damage has actually been fixed. All that needs to change is what your brain thinks of what is going on.

So what happens if your brain thought something was wrong when nothing actually was, and then for whatever complex, chaotic, emergent reasons thought that acupuncture had fixed it?

Well, acupuncture would have, quite literally, cured your pain.

I want to be very clear here that this does not mean I’m advocating acupuncture as a treatment. Given the right context, just about any experience you could imagine, if it hits your brain at just the right time and angle, has some chance of convincing your brain everything is fine. The fact that acupuncture may possibly do this does not meaningfully distinguish it from homeopathy, prayer, or exorcism.

But I do think it’s an idea worth thinking about. Anything that changes the context in which your brain processes physical experiences has the potential to change the nature of those experiences, e.g. to make things hurt or not hurt. Anything at all. Because our brains are generally very good at evaluating context effectively, we don’t notice how powerful this influence is, but it’s always there and it has significant implications for thinking about pain and the placebo effect5.

1 Explain Pain (2013)

2 Video of him telling the story

3 Original post where I wrote this summary of the story

4  Though both sham acupuncture and regular acupuncture to slightly outperform nothing at all, which has led to some fascinating hypotheses about why that may be the case.

5 A good example of these implications are some of the studies that have shown that educating pain patients about pain actually reduces their experiences of pain.

By ResearchToBeDone Posted in other