Placebo effects and personalised medicine

Placebo is Latin for, “I will please.” It’s also the name given to the effect where a person’s expectation of a positive outcome from an intervention produces a real clinical benefit despite the absence in some cases of any “real” therapeutic content. Literally, telling someone they’re going to feel relief from a painkiller produces analgesia even if you just inject them with saline. But in the era of personalised medicine, where treatments are tailor made to patients, might - Dasha Sandra wondered - there be an additional placebo effect just because someone regards the treatment as personal and therefore a bit more “special”. The answer is, as she explains to Chris Smith, there is!

Dasha -  We went first for a proof of concept in the lab with healthy participants. We invited people to the lab for a pain study where they received heat stimulations on their forearm multiple times. And on half of those stimulations, they received a machine that they could use to reduce their pain. So this was presented as an analgesic machine, but in reality it was a placebo. And for half of those participants, we made them believe that it was personalised. And for the other half we told them that it was generally effective and used in hospitals. And to personalise it, we went through this very elaborate procedure with multiple sham tests and false feedback that we pretended to apply to the machine so that they really saw that it was personalised to their genetics.

Chris -  And the outcome measure was how much heat you could apply to them before they said 'Ouch!'?

Dasha -  We applied the same level of heat that they rated as, for example, level 6 out of 10 pain. And they would rate that pain intensity. So they would say yes, this felt like a 60 out of a 100. We gave them the same heat stimulation, both on the trials with and without the machine. And then we compared when they were using this placebo machine, they actually rated their pain intensity as lower.

Chris -  How much of an effect was there when you said to the people who were getting the personalised - let's call it that the "personalised" pain relief - you're going to get pain relief. Now, how much less pain did they feel compared to people who just thought the machine was there for some pain relief?

Dasha -  So close to six points reduction on a scale of a hundred, which was relatively small in sort of general terms, but if you compare it to the control condition where they thought that it was generally effective, there was no pain relief there. So comparatively it was a lot larger.

Chris - That's an average though, I presume, isn't it? So were there any people in the study - because we're talking here about personalised medicine! - were there any people for whom this particular thing appeared to be extremely effective and some for whom it was less effective?

Dasha -  Yes, absolutely. So there may have been some personality effects that contributed to some people benefiting from this sort of quote unquote 'personalisation', more so there was one personality trait needed for uniqueness or the desire to be seen as different from others that had this kind of moderating effect. So people who wanted to be seen as different and scored high on that benefited from the treatment the most if it was presented as personalised to them.

Chris -  And, considering the mechanism, I mean obviously that's not what you set out to find, you were looking at the impact of the intervention rather than how it might be working, but is this just an extension of the placebo effect in the same way that if I give you an injection, I tend to get more of a dramatic response reported by you than if I feed you a pill or rub your back or something. Is it that people think because it's an enhanced intervention, it produces a greater effect? Is that how you think this works?

Dasha -  It could be. There are several possible ways that it could be working, and that is something that we need to understand further. So in this particular study, we really went with a very precise purpose to find "does this exist" - does the allure of personalisation contribute to the placebo effect? And we found that it did. Now, whether this is a different type of placebo effect or whether there was a compounded interaction with other contextual factors is sort of up for debate right now. We think that this is a different kind of placebo effect that was specific to personalisation, but it is only the first study. And so we would definitely need to look more into the mechanism.